Sponge

15 files changed, 948 insertions, 1264 deletions

diff --git a/src/OSSupport/CMakeLists.txt b/src/OSSupport/CMakeLists.txt
index 9424b63da..81b37ef0e 100644
--- a/src/OSSupport/CMakeLists.txt
+++ b/src/OSSupport/CMakeLists.txt
@@ -13,14 +13,12 @@ SET (SRCS
 	HostnameLookup.cpp
 	IPLookup.cpp
 	IsThread.cpp
-	ListenThread.cpp
 	NetworkSingleton.cpp
 	Semaphore.cpp
 	ServerHandleImpl.cpp
-	Socket.cpp
-	SocketThreads.cpp
 	StackTrace.cpp
 	TCPLinkImpl.cpp
+	UDPEndpointImpl.cpp
 )
 
 SET (HDRS
@@ -32,16 +30,14 @@ SET (HDRS
 	HostnameLookup.h
 	IPLookup.h
 	IsThread.h
-	ListenThread.h
 	Network.h
 	NetworkSingleton.h
 	Queue.h
 	Semaphore.h
 	ServerHandleImpl.h
-	Socket.h
-	SocketThreads.h
 	StackTrace.h
 	TCPLinkImpl.h
+	UDPEndpointImpl.h
 )
 
 if(NOT MSVC)
@@ -52,6 +48,6 @@ if(NOT MSVC)
 			target_link_libraries(OSSupport rt)
 		endif()
 
-		target_link_libraries(OSSupport pthread)
+		target_link_libraries(OSSupport pthread event_core event_extra)
 	endif()
 endif()
diff --git a/src/OSSupport/File.h b/src/OSSupport/File.h
index dfb38e839..ac6d1ab21 100644
--- a/src/OSSupport/File.h
+++ b/src/OSSupport/File.h
@@ -126,7 +126,7 @@ public:
 	
 	/** Returns the entire contents of the specified file as a string. Returns empty string on error. */
 	static AString ReadWholeFile(const AString & a_FileName);
-	
+
 	// tolua_end
 	
 	/** Returns the list of all items in the specified folder (files, folders, nix pipes, whatever's there). */
diff --git a/src/OSSupport/HostnameLookup.cpp b/src/OSSupport/HostnameLookup.cpp
index 3a2997ffd..0944153be 100644
--- a/src/OSSupport/HostnameLookup.cpp
+++ b/src/OSSupport/HostnameLookup.cpp
@@ -69,12 +69,24 @@ void cHostnameLookup::Callback(int a_ErrCode, evutil_addrinfo * a_Addr, void * a
 			case AF_INET:  // IPv4
 			{
 				sockaddr_in * sin = reinterpret_cast<sockaddr_in *>(a_Addr->ai_addr);
+				if (!Self->m_Callbacks->OnNameResolvedV4(Self->m_Hostname, sin))
+				{
+					// Callback indicated that the IP shouldn't be serialized to a string, just continue with the next address:
+					HasResolved = true;
+					continue;
+				}
 				evutil_inet_ntop(AF_INET, &(sin->sin_addr), IP, sizeof(IP));
 				break;
 			}
 			case AF_INET6:  // IPv6
 			{
 				sockaddr_in6 * sin = reinterpret_cast<sockaddr_in6 *>(a_Addr->ai_addr);
+				if (!Self->m_Callbacks->OnNameResolvedV6(Self->m_Hostname, sin))
+				{
+					// Callback indicated that the IP shouldn't be serialized to a string, just continue with the next address:
+					HasResolved = true;
+					continue;
+				}
 				evutil_inet_ntop(AF_INET6, &(sin->sin6_addr), IP, sizeof(IP));
 				break;
 			}
diff --git a/src/OSSupport/ListenThread.cpp b/src/OSSupport/ListenThread.cpp
deleted file mode 100644
index b029634e9..000000000
--- a/src/OSSupport/ListenThread.cpp
+++ /dev/null
@@ -1,238 +0,0 @@
-
-// ListenThread.cpp
-
-// Implements the cListenThread class representing the thread that listens for client connections
-
-#include "Globals.h"
-#include "ListenThread.h"
-
-
-
-
-
-cListenThread::cListenThread(cCallback & a_Callback, cSocket::eFamily a_Family, const AString & a_ServiceName) :
-	super(Printf("ListenThread %s", a_ServiceName.c_str())),
-	m_Callback(a_Callback),
-	m_Family(a_Family),
-	m_ShouldReuseAddr(false),
-	m_ServiceName(a_ServiceName)
-{
-}
-
-
-
-
-
-cListenThread::~cListenThread()
-{
-	Stop();
-}
-
-
-
-
-
-bool cListenThread::Initialize(const AString & a_PortsString)
-{
-	ASSERT(m_Sockets.empty());  // Not yet started
-	
-	if (!CreateSockets(a_PortsString))
-	{
-		return false;
-	}
-	
-	return true;
-}
-
-
-
-
-
-bool cListenThread::Start(void)
-{
-	if (m_Sockets.empty())
-	{
-		// There are no sockets listening, either forgotten to initialize or the user specified no listening ports
-		// Report as successful, though
-		return true;
-	}
-	return super::Start();
-}
-
-
-
-
-
-void cListenThread::Stop(void)
-{
-	if (m_Sockets.empty())
-	{
-		// No sockets means no thread was running in the first place
-		return;
-	}
-
-	m_ShouldTerminate = true;
-	
-	// Close one socket to wake the thread up from the select() call
-	m_Sockets[0].CloseSocket();
-	
-	// Wait for the thread to finish
-	super::Wait();
-	
-	// Close all the listening sockets:
-	for (cSockets::iterator itr = m_Sockets.begin() + 1, end = m_Sockets.end(); itr != end; ++itr)
-	{
-		itr->CloseSocket();
-	}  // for itr - m_Sockets[]
-	m_Sockets.clear();
-}
-
-
-
-
-
-void cListenThread::SetReuseAddr(bool a_Reuse)
-{
-	ASSERT(m_Sockets.empty());  // Must not have been Initialize()d yet
-	
-	m_ShouldReuseAddr = a_Reuse;
-}
-
-
-
-
-
-bool cListenThread::CreateSockets(const AString & a_PortsString)
-{
-	AStringVector Ports = StringSplitAndTrim(a_PortsString, ",");
-	
-	if (Ports.empty())
-	{
-		return false;
-	}
-	
-	AString FamilyStr = m_ServiceName;
-	switch (m_Family)
-	{
-		case cSocket::IPv4: FamilyStr.append(" IPv4"); break;
-		case cSocket::IPv6: FamilyStr.append(" IPv6"); break;
-		default:
-		{
-			ASSERT(!"Unknown address family");
-			break;
-		}
-	}
-	
-	for (AStringVector::const_iterator itr = Ports.begin(), end = Ports.end(); itr != end; ++itr)
-	{
-		int Port = atoi(itr->c_str());
-		if ((Port <= 0) || (Port > 65535))
-		{
-			LOGWARNING("%s: Invalid port specified: \"%s\".", FamilyStr.c_str(), itr->c_str());
-			continue;
-		}
-		m_Sockets.push_back(cSocket::CreateSocket(m_Family));
-		if (!m_Sockets.back().IsValid())
-		{
-			LOGWARNING("%s: Cannot create listening socket for port %d: \"%s\"", FamilyStr.c_str(), Port, cSocket::GetLastErrorString().c_str());
-			m_Sockets.pop_back();
-			continue;
-		}
-
-		if (m_ShouldReuseAddr)
-		{
-			if (!m_Sockets.back().SetReuseAddress())
-			{
-				LOG("%s: Port %d cannot reuse addr, syscall failed: \"%s\".", FamilyStr.c_str(), Port, cSocket::GetLastErrorString().c_str());
-			}
-		}
-		
-		// Bind to port:
-		bool res = false;
-		switch (m_Family)
-		{
-			case cSocket::IPv4: res = m_Sockets.back().BindToAnyIPv4(Port); break;
-			case cSocket::IPv6: res = m_Sockets.back().BindToAnyIPv6(Port); break;
-			default:
-			{
-				ASSERT(!"Unknown address family");
-				res = false;
-			}
-		}
-		if (!res)
-		{
-			LOGWARNING("%s: Cannot bind port %d: \"%s\".", FamilyStr.c_str(), Port, cSocket::GetLastErrorString().c_str());
-			m_Sockets.pop_back();
-			continue;
-		}
-		
-		if (!m_Sockets.back().Listen())
-		{
-			LOGWARNING("%s: Cannot listen on port %d: \"%s\".", FamilyStr.c_str(), Port, cSocket::GetLastErrorString().c_str());
-			m_Sockets.pop_back();
-			continue;
-		}
-		
-		LOGINFO("%s: Port %d is open for connections", FamilyStr.c_str(), Port);
-	}  // for itr - Ports[]
-	
-	return !(m_Sockets.empty());
-}
-
-
-
-
-
-void cListenThread::Execute(void)
-{
-	if (m_Sockets.empty())
-	{
-		LOGD("Empty cListenThread, ending thread now.");
-		return;
-	}
-	
-	// Find the highest socket number:
-	cSocket::xSocket Highest = m_Sockets[0].GetSocket();
-	for (cSockets::iterator itr = m_Sockets.begin(), end = m_Sockets.end(); itr != end; ++itr)
-	{
-		if (itr->GetSocket() > Highest)
-		{
-			Highest = itr->GetSocket();
-		}
-	}  // for itr - m_Sockets[]
-
-	while (!m_ShouldTerminate)
-	{
-		// Put all sockets into a FD set:
-		fd_set fdRead;
-		FD_ZERO(&fdRead);
-		for (cSockets::iterator itr = m_Sockets.begin(), end = m_Sockets.end(); itr != end; ++itr)
-		{
-			FD_SET(itr->GetSocket(), &fdRead);
-		}  // for itr - m_Sockets[]
-		
-		timeval tv;  // On Linux select() doesn't seem to wake up when socket is closed, so let's kinda busy-wait:
-		tv.tv_sec = 1;
-		tv.tv_usec = 0;
-		if (select((int)Highest + 1, &fdRead, nullptr, nullptr, &tv) == -1)
-		{
-			LOG("select(R) call failed in cListenThread: \"%s\"", cSocket::GetLastErrorString().c_str());
-			continue;
-		}
-		for (cSockets::iterator itr = m_Sockets.begin(), end = m_Sockets.end(); itr != end; ++itr)
-		{
-			if (itr->IsValid() && FD_ISSET(itr->GetSocket(), &fdRead))
-			{
-				cSocket Client = (m_Family == cSocket::IPv4) ? itr->AcceptIPv4() : itr->AcceptIPv6();
-				if (Client.IsValid())
-				{
-					m_Callback.OnConnectionAccepted(Client);
-				}
-			}
-		}  // for itr - m_Sockets[]
-	}  // while (!m_ShouldTerminate)
-}
-
-
-
-
diff --git a/src/OSSupport/ListenThread.h b/src/OSSupport/ListenThread.h
deleted file mode 100644
index b2d806c82..000000000
--- a/src/OSSupport/ListenThread.h
+++ /dev/null
@@ -1,85 +0,0 @@
-
-// ListenThread.h
-
-// Declares the cListenThread class representing the thread that listens for client connections
-
-
-
-
-
-#pragma once
-
-#include "IsThread.h"
-#include "Socket.h"
-
-
-
-
-
-// fwd:
-class cServer;
-
-
-
-
-
-class cListenThread :
-	public cIsThread
-{
-	typedef cIsThread super;
-	
-public:
-	/** Used as the callback for connection events */
-	class cCallback
-	{
-	public:
-		virtual ~cCallback() {}
-		
-		/** This callback is called whenever a socket connection is accepted */
-		virtual void OnConnectionAccepted(cSocket & a_Socket) = 0;
-	} ;
-	
-	cListenThread(cCallback & a_Callback, cSocket::eFamily a_Family, const AString & a_ServiceName = "");
-	~cListenThread();
-	
-	/** Creates all the sockets, returns trus if successful, false if not. */
-	bool Initialize(const AString & a_PortsString);
-	
-	bool Start(void);
-	
-	void Stop(void);
-	
-	/** Call before Initialize() to set the "reuse" flag on the sockets */
-	void SetReuseAddr(bool a_Reuse = true);
-	
-protected:
-	typedef std::vector<cSocket> cSockets;
-
-	/** The callback which to notify of incoming connections	 */
-	cCallback & m_Callback;
-	
-	/** Socket address family to use */
-	cSocket::eFamily m_Family;
-	
-	/** Sockets that are being monitored */
-	cSockets m_Sockets;
-	
-	/** If set to true, the SO_REUSEADDR socket option is set to true */
-	bool m_ShouldReuseAddr;
-	
-	/** Name of the service that's listening on the ports; for logging purposes only */
-	AString m_ServiceName;
-	
-	
-	/** Fills in m_Sockets with individual sockets, each for one port specified in a_PortsString.
-	Returns true if successful and at least one socket has been created
-	*/
-	bool CreateSockets(const AString & a_PortsString);
-	
-	// cIsThread override:
-	virtual void Execute(void) override;
-} ;
-
-
-
-
diff --git a/src/OSSupport/Network.h b/src/OSSupport/Network.h
index cdf6ba0e9..5dd596223 100644
--- a/src/OSSupport/Network.h
+++ b/src/OSSupport/Network.h
@@ -90,6 +90,9 @@ public:
 	Sends the RST packet, queued outgoing and incoming data is lost. */
 	virtual void Close(void) = 0;
 
+	/** Returns the callbacks that are used. */
+	cCallbacksPtr GetCallbacks(void) const { return m_Callbacks; }
+
 protected:
 	/** Callbacks to be used for the various situations. */
 	cCallbacksPtr m_Callbacks;
@@ -127,6 +130,64 @@ public:
 
 
 
+/** Interface that provides methods available on UDP communication endpoints. */
+class cUDPEndpoint
+{
+public:
+	/** Interface for the callbacks for events that can happen on the endpoint. */
+	class cCallbacks
+	{
+	public:
+		// Force a virtual destructor in all descendants:
+		virtual ~cCallbacks() {}
+
+		/** Called when an error occurs on the endpoint. */
+		virtual void OnError(int a_ErrorCode, const AString & a_ErrorMsg) = 0;
+
+		/** Called when there is an incoming datagram from a remote host. */
+		virtual void OnReceivedData(const char * a_Data, size_t a_Size, const AString & a_RemoteHost, UInt16 a_RemotePort) = 0;
+	};
+
+
+	// Force a virtual destructor for all descendants:
+	virtual ~cUDPEndpoint() {}
+
+	/** Closes the underlying socket.
+	Note that there still might be callbacks in-flight after this method returns. */
+	virtual void Close(void) = 0;
+
+	/** Returns true if the endpoint is open. */
+	virtual bool IsOpen(void) const = 0;
+
+	/** Returns the local port to which the underlying socket is bound. */
+	virtual UInt16 GetPort(void) const = 0;
+
+	/** Sends the specified payload in a single UDP datagram to the specified host+port combination.
+	Note that in order to send to a broadcast address, you need to call EnableBroadcasts() first. */
+	virtual bool Send(const AString & a_Payload, const AString & a_Host, UInt16 a_Port) = 0;
+
+	/** Marks the socket as capable of sending broadcast, using whatever OS API is needed.
+	Without this call, sending to a broadcast address using Send() may fail. */
+	virtual void EnableBroadcasts(void) = 0;
+
+protected:
+	/** The callbacks used for various events on the endpoint. */
+	cCallbacks & m_Callbacks;
+
+
+	/** Creates a new instance of an endpoint, with the specified callbacks. */
+	cUDPEndpoint(cCallbacks & a_Callbacks):
+		m_Callbacks(a_Callbacks)
+	{
+	}
+};
+
+typedef SharedPtr<cUDPEndpoint> cUDPEndpointPtr;
+
+
+
+
+
 class cNetwork
 {
 public:
@@ -180,9 +241,22 @@ public:
 
 		/** Called when the hostname is successfully resolved into an IP address.
 		May be called multiple times if a name resolves to multiple addresses.
-		a_IP may be either an IPv4 or an IPv6 address with their proper formatting. */
+		a_IP may be either an IPv4 or an IPv6 address with their proper formatting.
+		Each call to OnNameResolved() is preceded by a call to either OnNameResolvedV4() or OnNameResolvedV6(). */
 		virtual void OnNameResolved(const AString & a_Name, const AString & a_IP) = 0;
 
+		/** Called when the hostname is successfully resolved into an IPv4 address.
+		May be called multiple times if a name resolves to multiple addresses.
+		Each call to OnNameResolvedV4 is followed by OnNameResolved with the IP address serialized to a string.
+		If this callback returns false, the OnNameResolved() call is skipped for this address. */
+		virtual bool OnNameResolvedV4(const AString & a_Name, const sockaddr_in * a_IP) { return true; }
+
+		/** Called when the hostname is successfully resolved into an IPv6 address.
+		May be called multiple times if a name resolves to multiple addresses.
+		Each call to OnNameResolvedV4 is followed by OnNameResolved with the IP address serialized to a string.
+		If this callback returns false, the OnNameResolved() call is skipped for this address. */
+		virtual bool OnNameResolvedV6(const AString & a_Name, const sockaddr_in6 * a_IP) { return true; }
+
 		/** Called when an error is encountered while resolving.
 		If an error is reported, the OnFinished() callback is not called. */
 		virtual void OnError(int a_ErrorCode, const AString & a_ErrorMsg) = 0;
@@ -239,6 +313,11 @@ public:
 		const AString & a_IP,
 		cResolveNameCallbacksPtr a_Callbacks
 	);
+
+	/** Opens up an UDP endpoint for sending and receiving UDP datagrams on the specified port.
+	If a_Port is 0, the OS is free to assign any port number it likes to the endpoint.
+	Returns the endpoint object that can be interacted with. */
+	static cUDPEndpointPtr CreateUDPEndpoint(UInt16 a_Port, cUDPEndpoint::cCallbacks & a_Callbacks);
 };
 
 
diff --git a/src/OSSupport/NetworkSingleton.cpp b/src/OSSupport/NetworkSingleton.cpp
index 92f0604cd..358e24438 100644
--- a/src/OSSupport/NetworkSingleton.cpp
+++ b/src/OSSupport/NetworkSingleton.cpp
@@ -18,7 +18,8 @@
 
 
 
-cNetworkSingleton::cNetworkSingleton(void)
+cNetworkSingleton::cNetworkSingleton(void):
+	m_HasTerminated(false)
 {
 	// Windows: initialize networking:
 	#ifdef _WIN32
@@ -62,8 +63,7 @@ cNetworkSingleton::cNetworkSingleton(void)
 	}
 
 	// Create the event loop thread:
-	std::thread EventLoopThread(RunEventLoop, this);
-	EventLoopThread.detach();
+	m_EventLoopThread = std::thread(RunEventLoop, this);
 }
 
 
@@ -72,9 +72,32 @@ cNetworkSingleton::cNetworkSingleton(void)
 
 cNetworkSingleton::~cNetworkSingleton()
 {
+	// Check that Terminate has been called already:
+	ASSERT(m_HasTerminated);
+}
+
+
+
+
+
+cNetworkSingleton & cNetworkSingleton::Get(void)
+{
+	static cNetworkSingleton Instance;
+	return Instance;
+}
+
+
+
+
+
+void cNetworkSingleton::Terminate(void)
+{
+	ASSERT(!m_HasTerminated);
+	m_HasTerminated = true;
+
 	// Wait for the LibEvent event loop to terminate:
 	event_base_loopbreak(m_EventBase);
-	m_EventLoopTerminated.Wait();
+	m_EventLoopThread.join();
 
 	// Remove all objects:
 	{
@@ -96,16 +119,6 @@ cNetworkSingleton::~cNetworkSingleton()
 
 
 
-cNetworkSingleton & cNetworkSingleton::Get(void)
-{
-	static cNetworkSingleton Instance;
-	return Instance;
-}
-
-
-
-
-
 void cNetworkSingleton::LogCallback(int a_Severity, const char * a_Msg)
 {
 	switch (a_Severity)
@@ -129,7 +142,6 @@ void cNetworkSingleton::LogCallback(int a_Severity, const char * a_Msg)
 void cNetworkSingleton::RunEventLoop(cNetworkSingleton * a_Self)
 {
 	event_base_loop(a_Self->m_EventBase, EVLOOP_NO_EXIT_ON_EMPTY);
-	a_Self->m_EventLoopTerminated.Set();
 }
 
 
@@ -138,6 +150,7 @@ void cNetworkSingleton::RunEventLoop(cNetworkSingleton * a_Self)
 
 void cNetworkSingleton::AddHostnameLookup(cHostnameLookupPtr a_HostnameLookup)
 {
+	ASSERT(!m_HasTerminated);
 	cCSLock Lock(m_CS);
 	m_HostnameLookups.push_back(a_HostnameLookup);
 }
@@ -148,6 +161,7 @@ void cNetworkSingleton::AddHostnameLookup(cHostnameLookupPtr a_HostnameLookup)
 
 void cNetworkSingleton::RemoveHostnameLookup(const cHostnameLookup * a_HostnameLookup)
 {
+	ASSERT(!m_HasTerminated);
 	cCSLock Lock(m_CS);
 	for (auto itr = m_HostnameLookups.begin(), end = m_HostnameLookups.end(); itr != end; ++itr)
 	{
@@ -165,6 +179,7 @@ void cNetworkSingleton::RemoveHostnameLookup(const cHostnameLookup * a_HostnameL
 
 void cNetworkSingleton::AddIPLookup(cIPLookupPtr a_IPLookup)
 {
+	ASSERT(!m_HasTerminated);
 	cCSLock Lock(m_CS);
 	m_IPLookups.push_back(a_IPLookup);
 }
@@ -175,6 +190,7 @@ void cNetworkSingleton::AddIPLookup(cIPLookupPtr a_IPLookup)
 
 void cNetworkSingleton::RemoveIPLookup(const cIPLookup * a_IPLookup)
 {
+	ASSERT(!m_HasTerminated);
 	cCSLock Lock(m_CS);
 	for (auto itr = m_IPLookups.begin(), end = m_IPLookups.end(); itr != end; ++itr)
 	{
@@ -192,6 +208,7 @@ void cNetworkSingleton::RemoveIPLookup(const cIPLookup * a_IPLookup)
 
 void cNetworkSingleton::AddLink(cTCPLinkImplPtr a_Link)
 {
+	ASSERT(!m_HasTerminated);
 	cCSLock Lock(m_CS);
 	m_Connections.push_back(a_Link);
 }
@@ -202,6 +219,7 @@ void cNetworkSingleton::AddLink(cTCPLinkImplPtr a_Link)
 
 void cNetworkSingleton::RemoveLink(const cTCPLinkImpl * a_Link)
 {
+	ASSERT(!m_HasTerminated);
 	cCSLock Lock(m_CS);
 	for (auto itr = m_Connections.begin(), end = m_Connections.end(); itr != end; ++itr)
 	{
@@ -219,6 +237,7 @@ void cNetworkSingleton::RemoveLink(const cTCPLinkImpl * a_Link)
 
 void cNetworkSingleton::AddServer(cServerHandleImplPtr a_Server)
 {
+	ASSERT(!m_HasTerminated);
 	cCSLock Lock(m_CS);
 	m_Servers.push_back(a_Server);
 }
@@ -229,6 +248,7 @@ void cNetworkSingleton::AddServer(cServerHandleImplPtr a_Server)
 
 void cNetworkSingleton::RemoveServer(const cServerHandleImpl * a_Server)
 {
+	ASSERT(!m_HasTerminated);
 	cCSLock Lock(m_CS);
 	for (auto itr = m_Servers.begin(), end = m_Servers.end(); itr != end; ++itr)
 	{
diff --git a/src/OSSupport/NetworkSingleton.h b/src/OSSupport/NetworkSingleton.h
index 1d26fc8f4..0536a1c82 100644
--- a/src/OSSupport/NetworkSingleton.h
+++ b/src/OSSupport/NetworkSingleton.h
@@ -4,7 +4,8 @@
 // Declares the cNetworkSingleton class representing the storage for global data pertaining to network API
 // such as a list of all connections, all listening sockets and the LibEvent dispatch thread.
 
-// This is an internal header, no-one outside OSSupport should need to include it; use Network.h instead
+// This is an internal header, no-one outside OSSupport should need to include it; use Network.h instead;
+// the only exception being the main app entrypoint that needs to call Terminate before quitting.
 
 
 
@@ -48,6 +49,11 @@ public:
 	/** Returns the singleton instance of this class */
 	static cNetworkSingleton & Get(void);
 
+	/** Terminates all network-related threads.
+	To be used only on app shutdown.
+	MSVC runtime requires that the LibEvent networking be shut down before the main() function is exitted; this is the way to do it. */
+	void Terminate(void);
+
 	/** Returns the main LibEvent handle for event registering. */
 	event_base * GetEventBase(void) { return m_EventBase; }
 
@@ -110,8 +116,11 @@ protected:
 	/** Mutex protecting all containers against multithreaded access. */
 	cCriticalSection m_CS;
 
-	/** Event that gets signalled when the event loop terminates. */
-	cEvent m_EventLoopTerminated;
+	/** Set to true if Terminate has been called. */
+	volatile bool m_HasTerminated;
+
+	/** The thread in which the main LibEvent loop runs. */
+	std::thread m_EventLoopThread;
 
 
 	/** Initializes the LibEvent internals. */
diff --git a/src/OSSupport/ServerHandleImpl.cpp b/src/OSSupport/ServerHandleImpl.cpp
index ba38dbf2e..44ace448b 100644
--- a/src/OSSupport/ServerHandleImpl.cpp
+++ b/src/OSSupport/ServerHandleImpl.cpp
@@ -83,6 +83,9 @@ void cServerHandleImpl::Close(void)
 
 	// Remove the ptr to self, so that the object may be freed:
 	m_SelfPtr.reset();
+
+	// Remove self from cNetworkSingleton:
+	cNetworkSingleton::Get().RemoveServer(this);
 }
 
 
@@ -122,6 +125,7 @@ bool cServerHandleImpl::Listen(UInt16 a_Port)
 	bool NeedsTwoSockets = false;
 	int err;
 	evutil_socket_t MainSock = socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP);
+
 	if (!IsValidSocket(MainSock))
 	{
 		// Failed to create IPv6 socket, create an IPv4 one instead:
@@ -135,6 +139,16 @@ bool cServerHandleImpl::Listen(UInt16 a_Port)
 			return false;
 		}
 
+		// Allow the port to be reused right after the socket closes:
+		if (evutil_make_listen_socket_reuseable(MainSock) != 0)
+		{
+			m_ErrorCode = EVUTIL_SOCKET_ERROR();
+			Printf(m_ErrorMsg, "Port %d cannot be made reusable: %d (%s). Restarting the server might not work.",
+				a_Port, m_ErrorCode, evutil_socket_error_to_string(m_ErrorCode)
+			);
+			LOG("%s", m_ErrorMsg.c_str());
+		}
+
 		// Bind to all interfaces:
 		sockaddr_in name;
 		memset(&name, 0, sizeof(name));
@@ -157,14 +171,20 @@ bool cServerHandleImpl::Listen(UInt16 a_Port)
 			int res = setsockopt(MainSock, IPPROTO_IPV6, IPV6_V6ONLY, reinterpret_cast<const char *>(&Zero), sizeof(Zero));
 			err = EVUTIL_SOCKET_ERROR();
 			NeedsTwoSockets = ((res == SOCKET_ERROR) && (err == WSAENOPROTOOPT));
-			LOGD("setsockopt(IPV6_V6ONLY) returned %d, err is %d (%s). %s",
-				res, err, evutil_socket_error_to_string(err),
-				NeedsTwoSockets ? "Second socket will be created" : "Second socket not needed"
-			);
 		#else
 			setsockopt(MainSock, IPPROTO_IPV6, IPV6_V6ONLY, reinterpret_cast<const char *>(&Zero), sizeof(Zero));
 		#endif
 
+		// Allow the port to be reused right after the socket closes:
+		if (evutil_make_listen_socket_reuseable(MainSock) != 0)
+		{
+			m_ErrorCode = EVUTIL_SOCKET_ERROR();
+			Printf(m_ErrorMsg, "Port %d cannot be made reusable: %d (%s). Restarting the server might not work.",
+				a_Port, m_ErrorCode, evutil_socket_error_to_string(m_ErrorCode)
+			);
+			LOG("%s", m_ErrorMsg.c_str());
+		}
+
 		// Bind to all interfaces:
 		sockaddr_in6 name;
 		memset(&name, 0, sizeof(name));
@@ -194,6 +214,7 @@ bool cServerHandleImpl::Listen(UInt16 a_Port)
 	}
 	m_ConnListener = evconnlistener_new(cNetworkSingleton::Get().GetEventBase(), Callback, this, LEV_OPT_CLOSE_ON_FREE | LEV_OPT_REUSEABLE, 0, MainSock);
 	m_IsListening = true;
+
 	if (!NeedsTwoSockets)
 	{
 		return true;
@@ -202,6 +223,7 @@ bool cServerHandleImpl::Listen(UInt16 a_Port)
 	// If a secondary socket is required (WinXP dual-stack), create it here:
 	LOGD("Creating a second socket for IPv4");
 	evutil_socket_t SecondSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+
 	if (!IsValidSocket(SecondSock))
 	{
 		err = EVUTIL_SOCKET_ERROR();
@@ -209,6 +231,16 @@ bool cServerHandleImpl::Listen(UInt16 a_Port)
 		return true;  // Report as success, the primary socket is working
 	}
 
+	// Allow the port to be reused right after the socket closes:
+	if (evutil_make_listen_socket_reuseable(SecondSock) != 0)
+	{
+		m_ErrorCode = EVUTIL_SOCKET_ERROR();
+		Printf(m_ErrorMsg, "Port %d cannot be made reusable (second socket): %d (%s). Restarting the server might not work.",
+			a_Port, m_ErrorCode, evutil_socket_error_to_string(m_ErrorCode)
+		);
+		LOG("%s", m_ErrorMsg.c_str());
+	}
+
 	// Make the secondary socket nonblocking:
 	if (evutil_make_socket_nonblocking(SecondSock) != 0)
 	{
@@ -234,7 +266,7 @@ bool cServerHandleImpl::Listen(UInt16 a_Port)
 	if (listen(SecondSock, 0) != 0)
 	{
 		err = EVUTIL_SOCKET_ERROR();
-		LOGD("Cannot listen on on secondary socket on port %d: %d (%s)", a_Port, err, evutil_socket_error_to_string(err));
+		LOGD("Cannot listen on secondary socket on port %d: %d (%s)", a_Port, err, evutil_socket_error_to_string(err));
 		evutil_closesocket(SecondSock);
 		return true;  // Report as success, the primary socket is working
 	}
@@ -256,19 +288,20 @@ void cServerHandleImpl::Callback(evconnlistener * a_Listener, evutil_socket_t a_
 
 	// Get the textual IP address and port number out of a_Addr:
 	char IPAddress[128];
-	evutil_inet_ntop(a_Addr->sa_family, a_Addr->sa_data, IPAddress, ARRAYCOUNT(IPAddress));
 	UInt16 Port = 0;
 	switch (a_Addr->sa_family)
 	{
 		case AF_INET:
 		{
 			sockaddr_in * sin = reinterpret_cast<sockaddr_in *>(a_Addr);
+			evutil_inet_ntop(AF_INET, sin, IPAddress, ARRAYCOUNT(IPAddress));
 			Port = ntohs(sin->sin_port);
 			break;
 		}
 		case AF_INET6:
 		{
 			sockaddr_in6 * sin6 = reinterpret_cast<sockaddr_in6 *>(a_Addr);
+			evutil_inet_ntop(AF_INET, sin6, IPAddress, ARRAYCOUNT(IPAddress));
 			Port = ntohs(sin6->sin6_port);
 			break;
 		}
diff --git a/src/OSSupport/SocketThreads.cpp b/src/OSSupport/SocketThreads.cpp
deleted file mode 100644
index 153d6ed1d..000000000
--- a/src/OSSupport/SocketThreads.cpp
+++ /dev/null
@@ -1,702 +0,0 @@
-
-// cSocketThreads.cpp
-
-// Implements the cSocketThreads class representing the heart of MCS's client networking.
-// This object takes care of network communication, groups sockets into threads and uses as little threads as possible for full read / write support
-// For more detail, see http://forum.mc-server.org/showthread.php?tid=327
-
-#include "Globals.h"
-#include "SocketThreads.h"
-#include "Errors.h"
-
-
-
-
-
-////////////////////////////////////////////////////////////////////////////////
-// cSocketThreads:
-
-cSocketThreads::cSocketThreads(void)
-{
-}
-
-
-
-
-
-cSocketThreads::~cSocketThreads()
-{
-	for (cSocketThreadList::iterator itr = m_Threads.begin(); itr != m_Threads.end(); ++itr)
-	{
-		delete *itr;
-	}  // for itr - m_Threads[]
-	m_Threads.clear();
-}
-
-
-
-
-
-
-bool cSocketThreads::AddClient(const cSocket & a_Socket, cCallback * a_Client)
-{
-	// Add a (socket, client) pair for processing, data from a_Socket is to be sent to a_Client
-	
-	// Try to add to existing threads:
-	cCSLock Lock(m_CS);
-	for (cSocketThreadList::iterator itr = m_Threads.begin(); itr != m_Threads.end(); ++itr)
-	{
-		if ((*itr)->IsValid() && (*itr)->HasEmptySlot())
-		{
-			(*itr)->AddClient(a_Socket, a_Client);
-			return true;
-		}
-	}
-	
-	// No thread has free space, create a new one:
-	LOGD("Creating a new cSocketThread (currently have " SIZE_T_FMT ")", m_Threads.size());
-	cSocketThread * Thread = new cSocketThread(this);
-	if (!Thread->Start())
-	{
-		// There was an error launching the thread (but it was already logged along with the reason)
-		LOGERROR("A new cSocketThread failed to start");
-		delete Thread;
-		Thread = nullptr;
-		return false;
-	}
-	Thread->AddClient(a_Socket, a_Client);
-	m_Threads.push_back(Thread);
-	return true;
-}
-
-
-
-
-
-void cSocketThreads::RemoveClient(const cCallback * a_Client)
-{
-	// Remove the associated socket and the client from processing
-
-	cCSLock Lock(m_CS);
-	for (cSocketThreadList::iterator itr = m_Threads.begin(); itr != m_Threads.end(); ++itr)
-	{
-		if ((*itr)->RemoveClient(a_Client))
-		{
-			return;
-		}
-	}  // for itr - m_Threads[]
-
-	// This client wasn't found.
-	// It's not an error, because it may have been removed by a different thread in the meantime.
-}
-
-
-
-
-
-void cSocketThreads::NotifyWrite(const cCallback * a_Client)
-{
-	// Notifies the thread responsible for a_Client that the client has something to write
-
-	cCSLock Lock(m_CS);
-	for (cSocketThreadList::iterator itr = m_Threads.begin(); itr != m_Threads.end(); ++itr)
-	{
-		if ((*itr)->NotifyWrite(a_Client))
-		{
-			return;
-		}
-	}  // for itr - m_Threads[]
-	
-	// Cannot assert - this normally happens if a client disconnects and has pending packets, the cServer::cNotifyWriteThread will call this on invalid clients too
-	// ASSERT(!"Notifying write to an unknown client");
-}
-
-
-
-
-
-void cSocketThreads::Write(const cCallback * a_Client, const AString & a_Data)
-{
-	// Puts a_Data into outgoing data queue for a_Client
-	cCSLock Lock(m_CS);
-	for (cSocketThreadList::iterator itr = m_Threads.begin(); itr != m_Threads.end(); ++itr)
-	{
-		if ((*itr)->Write(a_Client, a_Data))
-		{
-			return;
-		}
-	}  // for itr - m_Threads[]
-	
-	// This may be perfectly legal, if the socket has been destroyed and the client is finishing up
-	// ASSERT(!"Writing to an unknown socket");
-}
-
-
-
-
-
-////////////////////////////////////////////////////////////////////////////////
-// cSocketThreads::cSocketThread:
-
-cSocketThreads::cSocketThread::cSocketThread(cSocketThreads * a_Parent) :
-	cIsThread("cSocketThread"),
-	m_Parent(a_Parent),
-	m_NumSlots(0)
-{
-	// Nothing needed yet
-}
-
-
-
-
-
-cSocketThreads::cSocketThread::~cSocketThread()
-{
-	m_ShouldTerminate = true;
-
-	// Notify the thread:
-	ASSERT(m_ControlSocket2.IsValid());
-	m_ControlSocket2.Send("a", 1);
-
-	// Wait for the thread to finish:
-	Wait();
-	
-	// Close the control sockets:
-	m_ControlSocket1.CloseSocket();
-	m_ControlSocket2.CloseSocket();
-}
-
-
-
-
-
-void cSocketThreads::cSocketThread::AddClient(const cSocket & a_Socket, cCallback * a_Client)
-{
-	ASSERT(m_Parent->m_CS.IsLockedByCurrentThread());
-	ASSERT(m_NumSlots < MAX_SLOTS);  // Use HasEmptySlot() to check before adding
-	
-	m_Slots[m_NumSlots].m_Client = a_Client;
-	m_Slots[m_NumSlots].m_Socket = a_Socket;
-	m_Slots[m_NumSlots].m_Socket.SetNonBlocking();
-	m_Slots[m_NumSlots].m_Outgoing.clear();
-	m_Slots[m_NumSlots].m_State = sSlot::ssNormal;
-	m_NumSlots++;
-	
-	// Notify the thread of the change:
-	ASSERT(m_ControlSocket2.IsValid());
-	m_ControlSocket2.Send("a", 1);
-}
-
-
-
-
-
-bool cSocketThreads::cSocketThread::RemoveClient(const cCallback * a_Client)
-{
-	ASSERT(m_Parent->m_CS.IsLockedByCurrentThread());
-	
-	if (m_NumSlots == 0)
-	{
-		return false;
-	}
-	
-	for (int i = m_NumSlots - 1; i >= 0 ; --i)
-	{
-		if (m_Slots[i].m_Client != a_Client)
-		{
-			continue;
-		}
-		
-		// Found the slot:
-		if (m_Slots[i].m_State == sSlot::ssRemoteClosed)
-		{
-			// The remote has already closed the socket, remove the slot altogether:
-			if (m_Slots[i].m_Socket.IsValid())
-			{
-				m_Slots[i].m_Socket.CloseSocket();
-			}
-			m_Slots[i] = m_Slots[--m_NumSlots];
-		}
-		else
-		{
-			// Query and queue the last batch of outgoing data:
-			AString Data;
-			m_Slots[i].m_Client->GetOutgoingData(Data);
-			m_Slots[i].m_Outgoing.append(Data);
-			if (m_Slots[i].m_Outgoing.empty())
-			{
-				// No more outgoing data, shut the socket down immediately:
-				m_Slots[i].m_Socket.ShutdownReadWrite();
-				m_Slots[i].m_State = sSlot::ssShuttingDown;
-			}
-			else
-			{
-				// More data to send, shut down reading and wait for the rest to get sent:
-				m_Slots[i].m_State = sSlot::ssWritingRestOut;
-			}
-			m_Slots[i].m_Client = nullptr;
-		}
-		
-		// Notify the thread of the change:
-		ASSERT(m_ControlSocket2.IsValid());
-		m_ControlSocket2.Send("r", 1);
-		return true;
-	}  // for i - m_Slots[]
-	
-	// Not found
-	return false;
-}
-
-
-
-
-
-bool cSocketThreads::cSocketThread::HasClient(const cCallback * a_Client) const
-{
-	ASSERT(m_Parent->m_CS.IsLockedByCurrentThread());
-
-	for (int i = m_NumSlots - 1; i >= 0; --i)
-	{
-		if (m_Slots[i].m_Client == a_Client)
-		{
-			return true;
-		}
-	}  // for i - m_Slots[]
-	return false;
-}
-
-
-
-
-
-bool cSocketThreads::cSocketThread::HasSocket(const cSocket * a_Socket) const
-{
-	for (int i = m_NumSlots - 1; i >= 0; --i)
-	{
-		if (m_Slots[i].m_Socket == *a_Socket)
-		{
-			return true;
-		}
-	}  // for i - m_Slots[]
-	return false;
-}
-
-
-
-
-
-bool cSocketThreads::cSocketThread::NotifyWrite(const cCallback * a_Client)
-{
-	ASSERT(m_Parent->m_CS.IsLockedByCurrentThread());
-
-	if (HasClient(a_Client))
-	{
-		// Notify the thread that there's another packet in the queue:
-		ASSERT(m_ControlSocket2.IsValid());
-		m_ControlSocket2.Send("q", 1);
-		return true;
-	}
-	return false;
-}
-
-
-
-
-
-bool cSocketThreads::cSocketThread::Write(const cCallback * a_Client, const AString & a_Data)
-{
-	ASSERT(m_Parent->m_CS.IsLockedByCurrentThread());
-	for (int i = m_NumSlots - 1; i >= 0; --i)
-	{
-		if (m_Slots[i].m_Client == a_Client)
-		{
-			m_Slots[i].m_Outgoing.append(a_Data);
-			
-			// Notify the thread that there's data in the queue:
-			ASSERT(m_ControlSocket2.IsValid());
-			m_ControlSocket2.Send("q", 1);
-			
-			return true;
-		}
-	}  // for i - m_Slots[]
-	return false;
-}
-
-
-
-
-
-bool cSocketThreads::cSocketThread::Start(void)
-{
-	// Create the control socket listener
-	m_ControlSocket2 = cSocket::CreateSocket(cSocket::IPv4);
-	if (!m_ControlSocket2.IsValid())
-	{
-		LOGERROR("Cannot create a Control socket for a cSocketThread (\"%s\"); continuing, but server may be unreachable from now on.", cSocket::GetLastErrorString().c_str());
-		return false;
-	}
-	if (!m_ControlSocket2.BindToLocalhostIPv4(cSocket::ANY_PORT))
-	{
-		LOGERROR("Cannot bind a Control socket for a cSocketThread (\"%s\"); continuing, but server may be unreachable from now on.", cSocket::GetLastErrorString().c_str());
-		m_ControlSocket2.CloseSocket();
-		return false;
-	}
-	if (!m_ControlSocket2.Listen(1))
-	{
-		LOGERROR("Cannot listen on a Control socket for a cSocketThread (\"%s\"); continuing, but server may be unreachable from now on.", cSocket::GetLastErrorString().c_str());
-		m_ControlSocket2.CloseSocket();
-		return false;
-	}
-	if (m_ControlSocket2.GetPort() == 0)
-	{
-		LOGERROR("Cannot determine Control socket port (\"%s\"); conitnuing, but the server may be unreachable from now on.", cSocket::GetLastErrorString().c_str());
-		m_ControlSocket2.CloseSocket();
-		return false;
-	}
-
-	// Start the thread
-	if (!super::Start())
-	{
-		LOGERROR("Cannot start new cSocketThread");
-		m_ControlSocket2.CloseSocket();
-		return false;
-	}
-	
-	// Finish connecting the control socket by accepting connection from the thread's socket
-	cSocket tmp = m_ControlSocket2.AcceptIPv4();
-	if (!tmp.IsValid())
-	{
-		LOGERROR("Cannot link Control sockets for a cSocketThread (\"%s\"); continuing, but server may be unreachable from now on.", cSocket::GetLastErrorString().c_str());
-		m_ControlSocket2.CloseSocket();
-		return false;
-	}
-	m_ControlSocket2.CloseSocket();
-	m_ControlSocket2 = tmp;
-	
-	return true;
-}
-
-
-
-
-
-void cSocketThreads::cSocketThread::Execute(void)
-{
-	// Connect the "client" part of the Control socket:
-	m_ControlSocket1 = cSocket::CreateSocket(cSocket::IPv4);
-	ASSERT(m_ControlSocket2.GetPort() != 0);  // We checked in the Start() method, but let's be sure
-	if (!m_ControlSocket1.ConnectToLocalhostIPv4(m_ControlSocket2.GetPort()))
-	{
-		LOGERROR("Cannot connect Control sockets for a cSocketThread (\"%s\"); continuing, but the server may be unreachable from now on.", cSocket::GetLastErrorString().c_str());
-		m_ControlSocket2.CloseSocket();
-		return;
-	}
-	
-	// The main thread loop:
-	while (!m_ShouldTerminate)
-	{
-		// Read outgoing data from the clients:
-		QueueOutgoingData();
-		
-		// Put sockets into the sets
-		fd_set fdRead;
-		fd_set fdWrite;
-		cSocket::xSocket Highest = m_ControlSocket1.GetSocket();
-		PrepareSets(&fdRead, &fdWrite, Highest);
-		
-		// Wait for the sockets:
-		timeval Timeout;
-		Timeout.tv_sec = 5;
-		Timeout.tv_usec = 0;
-		if (select((int)Highest + 1, &fdRead, &fdWrite, nullptr, &Timeout) == -1)
-		{
-			LOG("select() call failed in cSocketThread: \"%s\"", cSocket::GetLastErrorString().c_str());
-			continue;
-		}
-		
-		// Perform the IO:
-		ReadFromSockets(&fdRead);
-		WriteToSockets(&fdWrite);
-		CleanUpShutSockets();
-	}  // while (!mShouldTerminate)
-}
-
-
-
-
-
-void cSocketThreads::cSocketThread::PrepareSets(fd_set * a_Read, fd_set * a_Write, cSocket::xSocket & a_Highest)
-{
-	FD_ZERO(a_Read);
-	FD_ZERO(a_Write);
-	FD_SET(m_ControlSocket1.GetSocket(), a_Read);
-
-	cCSLock Lock(m_Parent->m_CS);
-	for (int i = m_NumSlots - 1; i >= 0; --i)
-	{
-		if (!m_Slots[i].m_Socket.IsValid())
-		{
-			continue;
-		}
-		if (m_Slots[i].m_State == sSlot::ssRemoteClosed)
-		{
-			// This socket won't provide nor consume any data anymore, don't put it in the Set
-			continue;
-		}
-		cSocket::xSocket s = m_Slots[i].m_Socket.GetSocket();
-		FD_SET(s, a_Read);
-		if (s > a_Highest)
-		{
-			a_Highest = s;
-		}
-		if (!m_Slots[i].m_Outgoing.empty())
-		{
-			// There's outgoing data for the socket, put it in the Write set
-			FD_SET(s, a_Write);
-		}
-	}  // for i - m_Slots[]
-}
-
-
-
-
-
-void cSocketThreads::cSocketThread::ReadFromSockets(fd_set * a_Read)
-{
-	// Read on available sockets:
-
-	// Reset Control socket state:
-	if (FD_ISSET(m_ControlSocket1.GetSocket(), a_Read))
-	{
-		char Dummy[128];
-		m_ControlSocket1.Receive(Dummy, sizeof(Dummy), 0);
-	}
-
-	// Read from clients:
-	cCSLock Lock(m_Parent->m_CS);
-	for (int i = m_NumSlots - 1; i >= 0; --i)
-	{
-		cSocket::xSocket Socket = m_Slots[i].m_Socket.GetSocket();
-		if (!cSocket::IsValidSocket(Socket) || !FD_ISSET(Socket, a_Read))
-		{
-			continue;
-		}
-		char Buffer[1024];
-		int Received = m_Slots[i].m_Socket.Receive(Buffer, ARRAYCOUNT(Buffer), 0);
-		if (Received <= 0)
-		{
-			if (cSocket::GetLastError() != cSocket::ErrWouldBlock)
-			{
-				// The socket has been closed by the remote party
-				switch (m_Slots[i].m_State)
-				{
-					case sSlot::ssNormal:
-					{
-						// Close the socket on our side:
-						m_Slots[i].m_State = sSlot::ssRemoteClosed;
-						m_Slots[i].m_Socket.CloseSocket();
-
-						// Notify the callback that the remote has closed the socket, *after* removing the socket:
-						cCallback * client = m_Slots[i].m_Client;
-						m_Slots[i] = m_Slots[--m_NumSlots];
-						if (client != nullptr)
-						{
-							client->SocketClosed();
-						}
-						break;
-					}
-					case sSlot::ssWritingRestOut:
-					case sSlot::ssShuttingDown:
-					case sSlot::ssShuttingDown2:
-					{
-						// Force-close the socket and remove the slot:
-						m_Slots[i].m_Socket.CloseSocket();
-						m_Slots[i] = m_Slots[--m_NumSlots];
-						break;
-					}
-					default:
-					{
-						LOG("%s: Unexpected socket state: %d (%s)",
-							__FUNCTION__, m_Slots[i].m_Socket.GetSocket(), m_Slots[i].m_Socket.GetIPString().c_str()
-						);
-						ASSERT(!"Unexpected socket state");
-						break;
-					}
-				}  // switch (m_Slots[i].m_State)
-			}
-		}
-		else
-		{
-			if (m_Slots[i].m_Client != nullptr)
-			{
-				m_Slots[i].m_Client->DataReceived(Buffer, Received);
-			}
-		}
-	}  // for i - m_Slots[]
-}
-
-
-
-
-
-void cSocketThreads::cSocketThread::WriteToSockets(fd_set * a_Write)
-{
-	// Write to available client sockets:
-	cCSLock Lock(m_Parent->m_CS);
-	for (int i = m_NumSlots - 1; i >= 0; --i)
-	{
-		cSocket::xSocket Socket = m_Slots[i].m_Socket.GetSocket();
-		if (!cSocket::IsValidSocket(Socket) || !FD_ISSET(Socket, a_Write))
-		{
-			continue;
-		}
-		if (m_Slots[i].m_Outgoing.empty())
-		{
-			// Request another chunk of outgoing data:
-			if (m_Slots[i].m_Client != nullptr)
-			{
-				AString Data;
-				m_Slots[i].m_Client->GetOutgoingData(Data);
-				m_Slots[i].m_Outgoing.append(Data);
-			}
-			if (m_Slots[i].m_Outgoing.empty())
-			{
-				// No outgoing data is ready
-				if (m_Slots[i].m_State == sSlot::ssWritingRestOut)
-				{
-					m_Slots[i].m_State = sSlot::ssShuttingDown;
-					m_Slots[i].m_Socket.ShutdownReadWrite();
-				}
-				continue;
-			}
-		}  // if (outgoing data is empty)
-		
-		if (m_Slots[i].m_State == sSlot::ssRemoteClosed)
-		{
-			continue;
-		}
-		
-		if (!SendDataThroughSocket(m_Slots[i].m_Socket, m_Slots[i].m_Outgoing))
-		{
-			int Err = cSocket::GetLastError();
-			LOGWARNING("Error %d while writing to client \"%s\", disconnecting. \"%s\"", Err, m_Slots[i].m_Socket.GetIPString().c_str(), GetOSErrorString(Err).c_str());
-			m_Slots[i].m_Socket.CloseSocket();
-			if (m_Slots[i].m_Client != nullptr)
-			{
-				m_Slots[i].m_Client->SocketClosed();
-			}
-			continue;
-		}
-		
-		if (m_Slots[i].m_Outgoing.empty() && (m_Slots[i].m_State == sSlot::ssWritingRestOut))
-		{
-			m_Slots[i].m_State = sSlot::ssShuttingDown;
-			m_Slots[i].m_Socket.ShutdownReadWrite();
-		}
-
-		// _X: If there's data left, it means the client is not reading fast enough, the server would unnecessarily spin in the main loop with zero actions taken; so signalling is disabled
-		// This means that if there's data left, it will be sent only when there's incoming data or someone queues another packet (for any socket handled by this thread)
-		/*
-		// If there's any data left, signalize the Control socket:
-		if (!m_Slots[i].m_Outgoing.empty())
-		{
-			ASSERT(m_ControlSocket2.IsValid());
-			m_ControlSocket2.Send("q", 1);
-		}
-		*/
-	}  // for i - m_Slots[i]
-}
-
-
-
-
-
-bool cSocketThreads::cSocketThread::SendDataThroughSocket(cSocket & a_Socket, AString & a_Data)
-{
-	// Send data in smaller chunks, so that the OS send buffers aren't overflown easily
-	while (!a_Data.empty())
-	{
-		size_t NumToSend = std::min(a_Data.size(), (size_t)1024);
-		int Sent = a_Socket.Send(a_Data.data(), NumToSend);
-		if (Sent < 0)
-		{
-			int Err = cSocket::GetLastError();
-			if (Err == cSocket::ErrWouldBlock)
-			{
-				// The OS send buffer is full, leave the outgoing data for the next time
-				return true;
-			}
-			// An error has occured
-			return false;
-		}
-		if (Sent == 0)
-		{
-			a_Socket.CloseSocket();
-			return true;
-		}
-		a_Data.erase(0, Sent);
-	}
-	return true;
-}
-
-
-
-
-
-void cSocketThreads::cSocketThread::CleanUpShutSockets(void)
-{
-	cCSLock Lock(m_Parent->m_CS);
-	for (int i = m_NumSlots - 1; i >= 0; i--)
-	{
-		switch (m_Slots[i].m_State)
-		{
-			case sSlot::ssShuttingDown2:
-			{
-				// The socket has reached the shutdown timeout, close it and clear its slot:
-				m_Slots[i].m_Socket.CloseSocket();
-				m_Slots[i] = m_Slots[--m_NumSlots];
-				break;
-			}
-			case sSlot::ssShuttingDown:
-			{
-				// The socket has been shut down for a single thread loop, let it loop once more before closing:
-				m_Slots[i].m_State = sSlot::ssShuttingDown2;
-				break;
-			}
-			default: break;
-		}
-	}  // for i - m_Slots[]
-}
-
-
-
-
-void cSocketThreads::cSocketThread::QueueOutgoingData(void)
-{
-	cCSLock Lock(m_Parent->m_CS);
-	for (int i = 0; i < m_NumSlots; i++)
-	{
-		if (m_Slots[i].m_Client != nullptr)
-		{
-			AString Data;
-			m_Slots[i].m_Client->GetOutgoingData(Data);
-			m_Slots[i].m_Outgoing.append(Data);
-		}
-		if (m_Slots[i].m_Outgoing.empty())
-		{
-			// No outgoing data is ready
-			if (m_Slots[i].m_State == sSlot::ssWritingRestOut)
-			{
-				// The socket doesn't want to be kept alive anymore, and doesn't have any remaining data to send.
-				// Shut it down and then close it after a timeout, or when the other side agrees
-				m_Slots[i].m_State = sSlot::ssShuttingDown;
-				m_Slots[i].m_Socket.ShutdownReadWrite();
-			}
-			continue;
-		}
-	}
-}
-
-
-
-
diff --git a/src/OSSupport/SocketThreads.h b/src/OSSupport/SocketThreads.h
deleted file mode 100644
index df819468d..000000000
--- a/src/OSSupport/SocketThreads.h
+++ /dev/null
@@ -1,194 +0,0 @@
-
-// SocketThreads.h
-
-// Interfaces to the cSocketThreads class representing the heart of MCS's client networking.
-// This object takes care of network communication, groups sockets into threads and uses as little threads as possible for full read / write support
-// For more detail, see http://forum.mc-server.org/showthread.php?tid=327
-
-/*
-Additional details:
-When a client wants to terminate the connection, they call the RemoveClient() function. This calls the
-callback one last time to read all the available outgoing data, putting it in the slot's m_OutgoingData
-buffer. Then it marks the slot as having no callback. The socket is kept alive until its outgoing data
-queue is empty, then shutdown is called on it and finally the socket is closed after a timeout.
-If at any time within this the remote end closes the socket, then the socket is closed directly.
-As soon as the socket is closed, the slot is finally removed from the SocketThread.
-The graph in $/docs/SocketThreads States.gv shows the state-machine transitions of the slot.
-*/
-
-
-
-
-
-/** How many clients should one thread handle? (must be less than FD_SETSIZE for your platform) */
-#define MAX_SLOTS 63
-
-
-
-
-
-#pragma once
-
-#include "Socket.h"
-#include "IsThread.h"
-
-
-
-
-// Check MAX_SLOTS:
-#if MAX_SLOTS >= FD_SETSIZE
-	#error "MAX_SLOTS must be less than FD_SETSIZE for your platform! (otherwise select() won't work)"
-#endif
-
-
-
-
-
-// fwd:
-class cSocket;
-class cClientHandle;
-
-
-
-
-
-class cSocketThreads
-{
-public:
-
-	// Clients of cSocketThreads must implement this interface to be able to communicate
-	class cCallback
-	{
-	public:
-		// Force a virtual destructor in all subclasses:
-		virtual ~cCallback() {}
-		
-		/** Called when data is received from the remote party.
-		SocketThreads does not care about the return value, others can use it for their specific purpose -
-		for example HTTPServer uses it to signal if the connection was terminated as a result of the data received. */
-		virtual bool DataReceived(const char * a_Data, size_t a_Size) = 0;
-		
-		/** Called when data can be sent to remote party
-		The function is supposed to *set* outgoing data to a_Data (overwrite) */
-		virtual void GetOutgoingData(AString & a_Data) = 0;
-		
-		/** Called when the socket has been closed for any reason */
-		virtual void SocketClosed(void) = 0;
-	} ;
-
-	
-	cSocketThreads(void);
-	~cSocketThreads();
-	
-	/** Add a (socket, client) pair for processing, data from a_Socket is to be sent to a_Client; returns true if successful */
-	bool AddClient(const cSocket & a_Socket, cCallback * a_Client);
-	
-	/** Remove the associated socket and the client from processing.
-	The socket is left to send its last outgoing data and is removed only after all its m_Outgoing is sent
-	and after the socket is properly shutdown (unless the remote disconnects before that)
-	*/
-	void RemoveClient(const cCallback * a_Client);
-	
-	/** Notify the thread responsible for a_Client that the client has something to write */
-	void NotifyWrite(const cCallback * a_Client);
-	
-	/** Puts a_Data into outgoing data queue for a_Client */
-	void Write(const cCallback * a_Client, const AString & a_Data);
-	
-private:
-
-	class cSocketThread :
-		public cIsThread
-	{
-		typedef cIsThread super;
-		
-	public:
-	
-		cSocketThread(cSocketThreads * a_Parent);
-		virtual ~cSocketThread();
-		
-		// All these methods assume parent's m_CS is locked
-		bool HasEmptySlot(void) const {return m_NumSlots < MAX_SLOTS; }
-		bool IsEmpty     (void) const {return m_NumSlots == 0; }
-
-		void AddClient   (const cSocket &   a_Socket, cCallback * a_Client);  // Takes ownership of the socket
-		bool RemoveClient(const cCallback * a_Client);  // Returns true if removed, false if not found
-		bool HasClient   (const cCallback * a_Client) const;
-		bool HasSocket   (const cSocket *   a_Socket) const;
-		bool NotifyWrite (const cCallback * a_Client);  // Returns true if client handled by this thread
-		bool Write       (const cCallback * a_Client, const AString & a_Data);  // Returns true if client handled by this thread
-		
-		bool Start(void);  // Hide the cIsThread's Start method, we need to provide our own startup to create the control socket
-		
-		bool IsValid(void) const {return m_ControlSocket2.IsValid(); }  // If the Control socket dies, the thread is not valid anymore
-		
-	private:
-	
-		cSocketThreads * m_Parent;
-	
-		// Two ends of the control socket, the first is select()-ed, the second is written to for notifications
-		cSocket m_ControlSocket1;
-		cSocket m_ControlSocket2;
-		
-		// Socket-client-dataqueues-state quadruplets.
-		// Manipulation with these assumes that the parent's m_CS is locked
-		struct sSlot
-		{
-			/** The socket is primarily owned by this object */
-			cSocket m_Socket;
-			
-			/** The callback to call for events. May be nullptr */
-			cCallback * m_Client;
-			
-			/** If sending writes only partial data, the rest is stored here for another send.
-			Also used when the slot is being removed to store the last batch of outgoing data. */
-			AString m_Outgoing;
-			
-			enum eState
-			{
-				ssNormal,          ///< Normal read / write operations
-				ssWritingRestOut,  ///< The client callback was removed, continue to send outgoing data
-				ssShuttingDown,    ///< The last outgoing data has been sent, the socket has called shutdown()
-				ssShuttingDown2,   ///< The shutdown has been done at least 1 thread loop ago (timeout detection)
-				ssRemoteClosed,    ///< The remote end has closed the connection (and we still have a client callback)
-			} m_State;
-		} ;
-		
-		sSlot m_Slots[MAX_SLOTS];
-		int   m_NumSlots;  // Number of slots actually used
-		
-		virtual void Execute(void) override;
-		
-		/** Prepares the Read and Write socket sets for select()
-		Puts all sockets into the read set, along with m_ControlSocket1.
-		Only sockets that have outgoing data queued on them are put in the write set.*/
-		void PrepareSets(fd_set * a_ReadSet, fd_set * a_WriteSet, cSocket::xSocket & a_Highest);
-		
-		/** Reads from sockets indicated in a_Read */
-		void ReadFromSockets(fd_set * a_Read);
-		
-		/** Writes to sockets indicated in a_Write */
-		void WriteToSockets (fd_set * a_Write);
-		
-		/** Sends data through the specified socket, trying to fill the OS send buffer in chunks.
-		Returns true if there was no error while sending, false if an error has occured.
-		Modifies a_Data to contain only the unsent data. */
-		bool SendDataThroughSocket(cSocket & a_Socket, AString & a_Data);
-
-		/** Removes those slots in ssShuttingDown2 state, sets those with ssShuttingDown state to ssShuttingDown2 */
-		void CleanUpShutSockets(void);
-		
-		/** Calls each client's callback to retrieve outgoing data for that client. */
-		void QueueOutgoingData(void);
-	} ;
-	
-	typedef std::list<cSocketThread *> cSocketThreadList;
-	
-	
-	cCriticalSection  m_CS;
-	cSocketThreadList m_Threads;
-} ;
-
-
-
-
diff --git a/src/OSSupport/TCPLinkImpl.cpp b/src/OSSupport/TCPLinkImpl.cpp
index b4cefa60c..c6f1978ad 100644
--- a/src/OSSupport/TCPLinkImpl.cpp
+++ b/src/OSSupport/TCPLinkImpl.cpp
@@ -7,6 +7,7 @@
 #include "TCPLinkImpl.h"
 #include "NetworkSingleton.h"
 #include "ServerHandleImpl.h"
+#include "event2/buffer.h"
 
 
 
@@ -17,8 +18,12 @@
 
 cTCPLinkImpl::cTCPLinkImpl(cTCPLink::cCallbacksPtr a_LinkCallbacks):
 	super(a_LinkCallbacks),
-	m_BufferEvent(bufferevent_socket_new(cNetworkSingleton::Get().GetEventBase(), -1, BEV_OPT_CLOSE_ON_FREE))
+	m_BufferEvent(bufferevent_socket_new(cNetworkSingleton::Get().GetEventBase(), -1, BEV_OPT_CLOSE_ON_FREE | BEV_OPT_THREADSAFE)),
+	m_LocalPort(0),
+	m_RemotePort(0),
+	m_ShouldShutdown(false)
 {
+	LOGD("Created new cTCPLinkImpl at %p with BufferEvent at %p", this, m_BufferEvent);
 }
 
 
@@ -27,9 +32,14 @@ cTCPLinkImpl::cTCPLinkImpl(cTCPLink::cCallbacksPtr a_LinkCallbacks):
 
 cTCPLinkImpl::cTCPLinkImpl(evutil_socket_t a_Socket, cTCPLink::cCallbacksPtr a_LinkCallbacks, cServerHandleImplPtr a_Server, const sockaddr * a_Address, socklen_t a_AddrLen):
 	super(a_LinkCallbacks),
-	m_BufferEvent(bufferevent_socket_new(cNetworkSingleton::Get().GetEventBase(), a_Socket, BEV_OPT_CLOSE_ON_FREE)),
-	m_Server(a_Server)
+	m_BufferEvent(bufferevent_socket_new(cNetworkSingleton::Get().GetEventBase(), a_Socket, BEV_OPT_CLOSE_ON_FREE | BEV_OPT_THREADSAFE)),
+	m_Server(a_Server),
+	m_LocalPort(0),
+	m_RemotePort(0),
+	m_ShouldShutdown(false)
 {
+	LOGD("Created new cTCPLinkImpl at %p with BufferEvent at %p", this, m_BufferEvent);
+
 	// Update the endpoint addresses:
 	UpdateLocalAddress();
 	UpdateAddress(a_Address, a_AddrLen, m_RemoteIP, m_RemotePort);
@@ -41,6 +51,7 @@ cTCPLinkImpl::cTCPLinkImpl(evutil_socket_t a_Socket, cTCPLink::cCallbacksPtr a_L
 
 cTCPLinkImpl::~cTCPLinkImpl()
 {
+	LOGD("Deleting cTCPLinkImpl at %p with BufferEvent at %p", this, m_BufferEvent);
 	bufferevent_free(m_BufferEvent);
 }
 
@@ -107,7 +118,7 @@ void cTCPLinkImpl::Enable(cTCPLinkImplPtr a_Self)
 	m_Self = a_Self;
 
 	// Set the LibEvent callbacks and enable processing:
-	bufferevent_setcb(m_BufferEvent, ReadCallback, nullptr, EventCallback, this);
+	bufferevent_setcb(m_BufferEvent, ReadCallback, WriteCallback, EventCallback, this);
 	bufferevent_enable(m_BufferEvent, EV_READ | EV_WRITE);
 }
 
@@ -117,6 +128,11 @@ void cTCPLinkImpl::Enable(cTCPLinkImplPtr a_Self)
 
 bool cTCPLinkImpl::Send(const void * a_Data, size_t a_Length)
 {
+	if (m_ShouldShutdown)
+	{
+		LOGD("%s: Cannot send data, the link is already shut down.", __FUNCTION__);
+		return false;
+	}
 	return (bufferevent_write(m_BufferEvent, a_Data, a_Length) == 0);
 }
 
@@ -126,12 +142,15 @@ bool cTCPLinkImpl::Send(const void * a_Data, size_t a_Length)
 
 void cTCPLinkImpl::Shutdown(void)
 {
-	#ifdef _WIN32
-		shutdown(bufferevent_getfd(m_BufferEvent), SD_SEND);
-	#else
-		shutdown(bufferevent_getfd(m_BufferEvent), SHUT_WR);
-	#endif
-	bufferevent_disable(m_BufferEvent, EV_WRITE);
+	// If there's no outgoing data, shutdown the socket directly:
+	if (evbuffer_get_length(bufferevent_get_output(m_BufferEvent)) == 0)
+	{
+		DoActualShutdown();
+		return;
+	}
+
+	// There's still outgoing data in the LibEvent buffer, schedule a shutdown when it's written to OS's TCP stack:
+	m_ShouldShutdown = true;
 }
 
 
@@ -177,8 +196,28 @@ void cTCPLinkImpl::ReadCallback(bufferevent * a_BufferEvent, void * a_Self)
 
 
 
+void cTCPLinkImpl::WriteCallback(bufferevent * a_BufferEvent, void * a_Self)
+{
+	ASSERT(a_Self != nullptr);
+	auto Self = static_cast<cTCPLinkImpl *>(a_Self);
+	ASSERT(Self->m_Callbacks != nullptr);
+
+	// If there's no more data to write and the link has been scheduled for shutdown, do the shutdown:
+	auto OutLen = evbuffer_get_length(bufferevent_get_output(Self->m_BufferEvent));
+	if ((OutLen == 0) && (Self->m_ShouldShutdown))
+	{
+		Self->DoActualShutdown();
+	}
+}
+
+
+
+
+
 void cTCPLinkImpl::EventCallback(bufferevent * a_BufferEvent, short a_What, void * a_Self)
 {
+	LOGD("cTCPLink event callback for link %p, BEV %p; what = 0x%02x", a_Self, a_BufferEvent, a_What);
+
 	ASSERT(a_Self != nullptr);
 	cTCPLinkImplPtr Self = static_cast<cTCPLinkImpl *>(a_Self)->m_Self;
 
@@ -215,6 +254,8 @@ void cTCPLinkImpl::EventCallback(bufferevent * a_BufferEvent, short a_What, void
 	// Pending connection succeeded, call the connection callback:
 	if (a_What & BEV_EVENT_CONNECTED)
 	{
+		Self->UpdateLocalAddress();
+		Self->UpdateRemoteAddress();
 		if (Self->m_ConnectCallbacks != nullptr)
 		{
 			Self->m_ConnectCallbacks->OnConnected(*Self);
@@ -222,8 +263,6 @@ void cTCPLinkImpl::EventCallback(bufferevent * a_BufferEvent, short a_What, void
 			Self->m_ConnectCallbacks.reset();
 			return;
 		}
-		Self->UpdateLocalAddress();
-		Self->UpdateRemoteAddress();
 	}
 
 	// If the connection has been closed, call the link callback and remove the connection:
@@ -310,6 +349,20 @@ void cTCPLinkImpl::UpdateRemoteAddress(void)
 
 
 
+void cTCPLinkImpl::DoActualShutdown(void)
+{
+	#ifdef _WIN32
+		shutdown(bufferevent_getfd(m_BufferEvent), SD_SEND);
+	#else
+		shutdown(bufferevent_getfd(m_BufferEvent), SHUT_WR);
+	#endif
+	bufferevent_disable(m_BufferEvent, EV_WRITE);
+}
+
+
+
+
+
 ////////////////////////////////////////////////////////////////////////////////
 // cNetwork API:
 
diff --git a/src/OSSupport/TCPLinkImpl.h b/src/OSSupport/TCPLinkImpl.h
index 735e8ed9d..bea21aeff 100644
--- a/src/OSSupport/TCPLinkImpl.h
+++ b/src/OSSupport/TCPLinkImpl.h
@@ -94,6 +94,11 @@ protected:
 	Initialized in Enable(), cleared in Close() and EventCallback(RemoteClosed). */
 	cTCPLinkImplPtr m_Self;
 
+	/** If true, Shutdown() has been called and is in queue.
+	No more data is allowed to be sent via Send() and after all the currently buffered
+	data is sent to the OS TCP stack, the socket gets shut down. */
+	bool m_ShouldShutdown;
+
 
 	/** Creates a new link to be queued to connect to a specified host:port.
 	Used for outgoing connections created using cNetwork::Connect().
@@ -104,6 +109,9 @@ protected:
 	/** Callback that LibEvent calls when there's data available from the remote peer. */
 	static void ReadCallback(bufferevent * a_BufferEvent, void * a_Self);
 
+	/** Callback that LibEvent calls when the remote peer can receive more data. */
+	static void WriteCallback(bufferevent * a_BufferEvent, void * a_Self);
+
 	/** Callback that LibEvent calls when there's a non-data-related event on the socket. */
 	static void EventCallback(bufferevent * a_BufferEvent, short a_What, void * a_Self);
 
@@ -115,6 +123,10 @@ protected:
 
 	/** Updates m_RemoteIP and m_RemotePort based on the metadata read from the socket. */
 	void UpdateRemoteAddress(void);
+
+	/** Calls shutdown on the link and disables LibEvent writing.
+	Called after all data from LibEvent buffers is sent to the OS TCP stack and shutdown() has been called before. */
+	void DoActualShutdown(void);
 };
 
 
diff --git a/src/OSSupport/UDPEndpointImpl.cpp b/src/OSSupport/UDPEndpointImpl.cpp
new file mode 100644
index 000000000..ece521ab8
--- /dev/null
+++ b/src/OSSupport/UDPEndpointImpl.cpp
@@ -0,0 +1,608 @@
+
+// UDPEndpointImpl.cpp
+
+// Implements the cUDPEndpointImpl class representing an implementation of an endpoint in UDP communication
+
+#include "Globals.h"
+#include "UDPEndpointImpl.h"
+#include "NetworkSingleton.h"
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// Globals:
+
+static bool IsValidSocket(evutil_socket_t a_Socket)
+{
+	#ifdef _WIN32
+		return (a_Socket != INVALID_SOCKET);
+	#else  // _WIN32
+		return (a_Socket >= 0);
+	#endif  // else _WIN32
+}
+
+
+
+
+
+/** Converts a_SrcAddr in IPv4 format to a_DstAddr in IPv6 format (using IPv4-mapped IPv6). */
+static void ConvertIPv4ToMappedIPv6(sockaddr_in & a_SrcAddr, sockaddr_in6 & a_DstAddr)
+{
+	memset(&a_DstAddr, 0, sizeof(a_DstAddr));
+	a_DstAddr.sin6_family = AF_INET6;
+	a_DstAddr.sin6_addr.s6_addr[10] = 0xff;
+	a_DstAddr.sin6_addr.s6_addr[11] = 0xff;
+	a_DstAddr.sin6_addr.s6_addr[12] = static_cast<Byte>((a_SrcAddr.sin_addr.s_addr >>  0) & 0xff);
+	a_DstAddr.sin6_addr.s6_addr[13] = static_cast<Byte>((a_SrcAddr.sin_addr.s_addr >>  8) & 0xff);
+	a_DstAddr.sin6_addr.s6_addr[14] = static_cast<Byte>((a_SrcAddr.sin_addr.s_addr >> 16) & 0xff);
+	a_DstAddr.sin6_addr.s6_addr[15] = static_cast<Byte>((a_SrcAddr.sin_addr.s_addr >> 24) & 0xff);
+	a_DstAddr.sin6_port = a_SrcAddr.sin_port;
+}
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cUDPSendAfterLookup:
+
+/** A hostname-to-IP resolver callback that sends the data stored within to the resolved IP address.
+This is used for sending UDP datagrams to hostnames, so that the cUDPEndpoint::Send() doesn't block.
+Instead an instance of this callback is queued for resolving and the data is sent once the IP is resolved. */
+class cUDPSendAfterLookup:
+	public cNetwork::cResolveNameCallbacks
+{
+public:
+	cUDPSendAfterLookup(const AString & a_Data, UInt16 a_Port, evutil_socket_t a_MainSock, evutil_socket_t a_SecondSock, bool a_IsMainSockIPv6):
+		m_Data(a_Data),
+		m_Port(a_Port),
+		m_MainSock(a_MainSock),
+		m_SecondSock(a_SecondSock),
+		m_IsMainSockIPv6(a_IsMainSockIPv6),
+		m_HasIPv4(false),
+		m_HasIPv6(false)
+	{
+	}
+
+protected:
+	/** The data to send after the hostname is resolved. */
+	AString m_Data;
+
+	/** The port to which to send the data. */
+	UInt16 m_Port;
+
+	/** The primary socket to use for sending. */
+	evutil_socket_t m_MainSock;
+
+	/** The secondary socket to use for sending, if needed by the OS. */
+	evutil_socket_t m_SecondSock;
+
+	/** True if m_MainSock is an IPv6 socket. */
+	bool m_IsMainSockIPv6;
+
+	/** The IPv4 address resolved, if any. */
+	sockaddr_in m_AddrIPv4;
+
+	/** Set to true if the name resolved to an IPv4 address. */
+	bool m_HasIPv4;
+
+	/** The IPv6 address resolved, if any. */
+	sockaddr_in6 m_AddrIPv6;
+
+	/** Set to true if the name resolved to an IPv6 address. */
+	bool m_HasIPv6;
+
+
+	// cNetwork::cResolveNameCallbacks overrides:
+	virtual void OnNameResolved(const AString & a_Name, const AString & a_PI) override
+	{
+		// Not needed
+	}
+
+	virtual bool OnNameResolvedV4(const AString & a_Name, const sockaddr_in * a_IP) override
+	{
+		if (!m_HasIPv4)
+		{
+			m_AddrIPv4 = *a_IP;
+			m_AddrIPv4.sin_port = htons(m_Port);
+			m_HasIPv4 = true;
+		}
+
+		// Don't want OnNameResolved() callback
+		return false;
+	}
+
+	virtual bool OnNameResolvedV6(const AString & a_Name, const sockaddr_in6 * a_IP) override
+	{
+		if (!m_HasIPv6)
+		{
+			m_AddrIPv6 = *a_IP;
+			m_AddrIPv6.sin6_port = htons(m_Port);
+			m_HasIPv6 = true;
+		}
+
+		// Don't want OnNameResolved() callback
+		return false;
+	}
+
+	virtual void OnFinished(void) override
+	{
+		// Send the actual data, through the correct socket and using the correct resolved address:
+		if (m_IsMainSockIPv6)
+		{
+			if (m_HasIPv6)
+			{
+				sendto(m_MainSock, m_Data.data(), static_cast<socklen_t>(m_Data.size()), 0, reinterpret_cast<const sockaddr *>(&m_AddrIPv6), static_cast<socklen_t>(sizeof(m_AddrIPv6)));
+			}
+			else if (m_HasIPv4)
+			{
+				// If the secondary socket is valid, it is an IPv4 socket, so use that:
+				if (m_SecondSock != -1)
+				{
+					sendto(m_SecondSock, m_Data.data(), static_cast<socklen_t>(m_Data.size()), 0, reinterpret_cast<const sockaddr *>(&m_AddrIPv4), static_cast<socklen_t>(sizeof(m_AddrIPv4)));
+				}
+				else
+				{
+					// Need an address conversion from IPv4 to IPv6-mapped-IPv4:
+					ConvertIPv4ToMappedIPv6(m_AddrIPv4, m_AddrIPv6);
+					sendto(m_MainSock, m_Data.data(), static_cast<socklen_t>(m_Data.size()), 0, reinterpret_cast<const sockaddr *>(&m_AddrIPv6), static_cast<socklen_t>(sizeof(m_AddrIPv6)));
+				}
+			}
+			else
+			{
+				LOGD("UDP endpoint queued sendto: Name not resolved");
+				return;
+			}
+		}
+		else  // m_IsMainSockIPv6
+		{
+			// Main socket is IPv4 only, only allow IPv4 dst address:
+			if (!m_HasIPv4)
+			{
+				LOGD("UDP endpoint queued sendto: Name not resolved to IPv4 for an IPv4-only socket");
+				return;
+			}
+			sendto(m_MainSock, m_Data.data(), static_cast<socklen_t>(m_Data.size()), 0, reinterpret_cast<const sockaddr *>(&m_AddrIPv4), static_cast<socklen_t>(sizeof(m_AddrIPv4)));
+		}
+	}
+
+	virtual void OnError(int a_ErrorCode, const AString & a_ErrorMsg) override
+	{
+		// Nothing needed
+	}
+};
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cUDPEndpointImpl:
+
+cUDPEndpointImpl::cUDPEndpointImpl(UInt16 a_Port, cUDPEndpoint::cCallbacks & a_Callbacks):
+	super(a_Callbacks),
+	m_Port(0),
+	m_MainSock(-1),
+	m_IsMainSockIPv6(true),
+	m_SecondarySock(-1),
+	m_MainEvent(nullptr),
+	m_SecondaryEvent(nullptr)
+{
+	Open(a_Port);
+}
+
+
+
+
+
+void cUDPEndpointImpl::Close(void)
+{
+	if (m_Port == 0)
+	{
+		// Already closed
+		return;
+	}
+
+	// Close the LibEvent handles:
+	if (m_MainEvent != nullptr)
+	{
+		event_free(m_MainEvent);
+		m_MainEvent = nullptr;
+	}
+	if (m_SecondaryEvent != nullptr)
+	{
+		event_free(m_SecondaryEvent);
+		m_SecondaryEvent = nullptr;
+	}
+
+	// Close the OS sockets:
+	evutil_closesocket(m_MainSock);
+	m_MainSock = -1;
+	evutil_closesocket(m_SecondarySock);
+	m_SecondarySock = -1;
+
+	// Mark as closed:
+	m_Port = 0;
+}
+
+
+
+
+
+bool cUDPEndpointImpl::IsOpen(void) const
+{
+	return (m_Port != 0);
+}
+
+
+
+
+
+UInt16 cUDPEndpointImpl::GetPort(void) const
+{
+	return m_Port;
+}
+
+
+
+
+
+bool cUDPEndpointImpl::Send(const AString & a_Payload, const AString & a_Host, UInt16 a_Port)
+{
+	// If a_Host is an IP address, send the data directly:
+	sockaddr_storage sa;
+	int salen = static_cast<int>(sizeof(sa));
+	memset(&sa, 0, sizeof(sa));
+	if (evutil_parse_sockaddr_port(a_Host.c_str(), reinterpret_cast<sockaddr *>(&sa), &salen) != 0)
+	{
+		// a_Host is a hostname, we need to do a lookup first:
+		auto queue = std::make_shared<cUDPSendAfterLookup>(a_Payload, a_Port, m_MainSock, m_SecondarySock, m_IsMainSockIPv6);
+		return cNetwork::HostnameToIP(a_Host, queue);
+	}
+
+	// a_Host is an IP address and has been parsed into "sa"
+	// Insert the correct port and send data:
+	int NumSent;
+	switch (sa.ss_family)
+	{
+		case AF_INET:
+		{
+			reinterpret_cast<sockaddr_in *>(&sa)->sin_port = htons(a_Port);
+			if (m_IsMainSockIPv6)
+			{
+				if (IsValidSocket(m_SecondarySock))
+				{
+					// The secondary socket, which is always IPv4, is present:
+					NumSent = static_cast<int>(sendto(m_SecondarySock, a_Payload.data(), static_cast<socklen_t>(a_Payload.size()), 0, reinterpret_cast<const sockaddr *>(&sa), static_cast<socklen_t>(salen)));
+				}
+				else
+				{
+					// Need to convert IPv4 to IPv6 address before sending:
+					sockaddr_in6 IPv6;
+					ConvertIPv4ToMappedIPv6(*reinterpret_cast<sockaddr_in *>(&sa), IPv6);
+					NumSent = static_cast<int>(sendto(m_MainSock, a_Payload.data(), static_cast<socklen_t>(a_Payload.size()), 0, reinterpret_cast<const sockaddr *>(&IPv6), static_cast<socklen_t>(sizeof(IPv6))));
+				}
+			}
+			else
+			{
+				NumSent = static_cast<int>(sendto(m_MainSock, a_Payload.data(), static_cast<socklen_t>(a_Payload.size()), 0, reinterpret_cast<const sockaddr *>(&sa), static_cast<socklen_t>(salen)));
+			}
+			break;
+		}
+
+		case AF_INET6:
+		{
+			reinterpret_cast<sockaddr_in6 *>(&sa)->sin6_port = htons(a_Port);
+			NumSent = static_cast<int>(sendto(m_MainSock, a_Payload.data(), static_cast<socklen_t>(a_Payload.size()), 0, reinterpret_cast<const sockaddr *>(&sa), static_cast<socklen_t>(salen)));
+			break;
+		}
+		default:
+		{
+			LOGD("UDP sendto: Invalid address family for address \"%s\".", a_Host.c_str());
+			return false;
+		}
+	}
+	return (NumSent > 0);
+}
+
+
+
+
+
+void cUDPEndpointImpl::EnableBroadcasts(void)
+{
+	ASSERT(IsOpen());
+
+	// Enable broadcasts on the main socket:
+	// Some OSes use ints, others use chars, so we try both
+	int broadcastInt = 1;
+	char broadcastChar = 1;
+	// (Note that Windows uses const char * for option values, while Linux uses const void *)
+	if (setsockopt(m_MainSock, SOL_SOCKET, SO_BROADCAST, reinterpret_cast<const char *>(&broadcastInt), sizeof(broadcastInt)) == -1)
+	{
+		if (setsockopt(m_MainSock, SOL_SOCKET, SO_BROADCAST, &broadcastChar, sizeof(broadcastChar)) == -1)
+		{
+			int err = EVUTIL_SOCKET_ERROR();
+			LOGWARNING("Cannot enable broadcasts on port %d: %d (%s)", m_Port, err, evutil_socket_error_to_string(err));
+			return;
+		}
+
+		// Enable broadcasts on the secondary socket, if opened (use char, it worked for primary):
+		if (IsValidSocket(m_SecondarySock))
+		{
+			if (setsockopt(m_SecondarySock, SOL_SOCKET, SO_BROADCAST, &broadcastChar, sizeof(broadcastChar)) == -1)
+			{
+				int err = EVUTIL_SOCKET_ERROR();
+				LOGWARNING("Cannot enable broadcasts on port %d (secondary): %d (%s)", m_Port, err, evutil_socket_error_to_string(err));
+			}
+		}
+		return;
+	}
+
+	// Enable broadcasts on the secondary socket, if opened (use int, it worked for primary):
+	if (IsValidSocket(m_SecondarySock))
+	{
+		if (setsockopt(m_SecondarySock, SOL_SOCKET, SO_BROADCAST, reinterpret_cast<const char *>(&broadcastInt), sizeof(broadcastInt)) == -1)
+		{
+			int err = EVUTIL_SOCKET_ERROR();
+			LOGWARNING("Cannot enable broadcasts on port %d (secondary): %d (%s)", m_Port, err, evutil_socket_error_to_string(err));
+		}
+	}
+}
+
+
+
+
+
+void cUDPEndpointImpl::Open(UInt16 a_Port)
+{
+	ASSERT(m_Port == 0);  // Must not be already open
+
+	// Make sure the cNetwork internals are innitialized:
+	cNetworkSingleton::Get();
+
+	// Set up the main socket:
+	// It should listen on IPv6 with IPv4 fallback, when available; IPv4 when IPv6 is not available.
+	bool NeedsTwoSockets = false;
+	m_IsMainSockIPv6 = true;
+	m_MainSock = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);
+
+	int err;
+	if (!IsValidSocket(m_MainSock))
+	{
+		// Failed to create IPv6 socket, create an IPv4 one instead:
+		m_IsMainSockIPv6 = false;
+		err = EVUTIL_SOCKET_ERROR();
+		LOGD("Failed to create IPv6 MainSock: %d (%s)", err, evutil_socket_error_to_string(err));
+		m_MainSock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+		if (!IsValidSocket(m_MainSock))
+		{
+			err = EVUTIL_SOCKET_ERROR();
+			m_Callbacks.OnError(err, Printf("Cannot create UDP socket for port %d: %s", a_Port, evutil_socket_error_to_string(err)));
+			return;
+		}
+
+		// Allow the port to be reused right after the socket closes:
+		if (evutil_make_listen_socket_reuseable(m_MainSock) != 0)
+		{
+			err = EVUTIL_SOCKET_ERROR();
+			LOG("UDP Port %d cannot be made reusable: %d (%s). Restarting the server might not work.",
+				a_Port, err, evutil_socket_error_to_string(err)
+			);
+		}
+
+		// Bind to all interfaces:
+		sockaddr_in name;
+		memset(&name, 0, sizeof(name));
+		name.sin_family = AF_INET;
+		name.sin_port = ntohs(a_Port);
+		if (bind(m_MainSock, reinterpret_cast<const sockaddr *>(&name), sizeof(name)) != 0)
+		{
+			err = EVUTIL_SOCKET_ERROR();
+			m_Callbacks.OnError(err, Printf("Cannot bind UDP port %d: %s", a_Port, evutil_socket_error_to_string(err)));
+			evutil_closesocket(m_MainSock);
+			return;
+		}
+	}
+	else
+	{
+		// IPv6 socket created, switch it into "dualstack" mode:
+		UInt32 Zero = 0;
+		#ifdef _WIN32
+			// WinXP doesn't support this feature, so if the setting fails, create another socket later on:
+			int res = setsockopt(m_MainSock, IPPROTO_IPV6, IPV6_V6ONLY, reinterpret_cast<const char *>(&Zero), sizeof(Zero));
+			err = EVUTIL_SOCKET_ERROR();
+			NeedsTwoSockets = ((res == SOCKET_ERROR) && (err == WSAENOPROTOOPT));
+		#else
+			setsockopt(m_MainSock, IPPROTO_IPV6, IPV6_V6ONLY, reinterpret_cast<const char *>(&Zero), sizeof(Zero));
+		#endif
+
+		// Allow the port to be reused right after the socket closes:
+		if (evutil_make_listen_socket_reuseable(m_MainSock) != 0)
+		{
+			err  = EVUTIL_SOCKET_ERROR();
+			LOG("UDP Port %d cannot be made reusable: %d (%s). Restarting the server might not work.",
+				a_Port, err, evutil_socket_error_to_string(err)
+			);
+		}
+
+		// Bind to all interfaces:
+		sockaddr_in6 name;
+		memset(&name, 0, sizeof(name));
+		name.sin6_family = AF_INET6;
+		name.sin6_port = ntohs(a_Port);
+		if (bind(m_MainSock, reinterpret_cast<const sockaddr *>(&name), sizeof(name)) != 0)
+		{
+			err = EVUTIL_SOCKET_ERROR();
+			m_Callbacks.OnError(err, Printf("Cannot bind to UDP port %d: %s", a_Port, evutil_socket_error_to_string(err)));
+			evutil_closesocket(m_MainSock);
+			return;
+		}
+	}
+	if (evutil_make_socket_nonblocking(m_MainSock) != 0)
+	{
+		err = EVUTIL_SOCKET_ERROR();
+		m_Callbacks.OnError(err, Printf("Cannot make socket on UDP port %d nonblocking: %s", a_Port, evutil_socket_error_to_string(err)));
+		evutil_closesocket(m_MainSock);
+		return;
+	}
+	m_MainEvent = event_new(cNetworkSingleton::Get().GetEventBase(), m_MainSock, EV_READ | EV_PERSIST, RawCallback, this);
+	event_add(m_MainEvent, nullptr);
+
+	// Read the actual port number on which the socket is listening:
+	{
+		sockaddr_storage name;
+		socklen_t namelen = static_cast<socklen_t>(sizeof(name));
+		getsockname(m_MainSock, reinterpret_cast<sockaddr *>(&name), &namelen);
+		switch (name.ss_family)
+		{
+			case AF_INET:
+			{
+				sockaddr_in * sin = reinterpret_cast<sockaddr_in *>(&name);
+				m_Port = ntohs(sin->sin_port);
+				break;
+			}
+			case AF_INET6:
+			{
+				sockaddr_in6 * sin6 = reinterpret_cast<sockaddr_in6 *>(&name);
+				m_Port = ntohs(sin6->sin6_port);
+				break;
+			}
+		}
+	}
+
+	// If we don't need to create another socket, bail out now:
+	if (!NeedsTwoSockets)
+	{
+		return;
+	}
+
+	// If a secondary socket is required (WinXP dual-stack), create it here:
+	LOGD("Creating a second UDP socket for IPv4");
+	m_SecondarySock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+
+	if (!IsValidSocket(m_SecondarySock))
+	{
+		// Don't report as an error, the primary socket is working
+		err = EVUTIL_SOCKET_ERROR();
+		LOGD("Socket creation failed for secondary UDP socket for port %d: %d, %s", m_Port, err, evutil_socket_error_to_string(err));
+		return;
+	}
+
+	// Allow the port to be reused right after the socket closes:
+	if (evutil_make_listen_socket_reuseable(m_SecondarySock) != 0)
+	{
+		// Don't report as an error, the primary socket is working
+		err = EVUTIL_SOCKET_ERROR();
+		LOGD("UDP Port %d cannot be made reusable (second socket): %d (%s). Restarting the server might not work.",
+			a_Port, err, evutil_socket_error_to_string(err)
+		);
+		evutil_closesocket(m_SecondarySock);
+		m_SecondarySock = -1;
+		return;
+	}
+
+	// Make the secondary socket nonblocking:
+	if (evutil_make_socket_nonblocking(m_SecondarySock) != 0)
+	{
+		// Don't report as an error, the primary socket is working
+		err = EVUTIL_SOCKET_ERROR();
+		LOGD("evutil_make_socket_nonblocking() failed for secondary UDP socket: %d, %s", err, evutil_socket_error_to_string(err));
+		evutil_closesocket(m_SecondarySock);
+		m_SecondarySock = -1;
+		return;
+	}
+
+	// Bind to all IPv4 interfaces:
+	sockaddr_in name;
+	memset(&name, 0, sizeof(name));
+	name.sin_family = AF_INET;
+	name.sin_port = ntohs(m_Port);
+	if (bind(m_SecondarySock, reinterpret_cast<const sockaddr *>(&name), sizeof(name)) != 0)
+	{
+		// Don't report as an error, the primary socket is working
+		err = EVUTIL_SOCKET_ERROR();
+		LOGD("Cannot bind secondary socket to UDP port %d: %d (%s)", m_Port, err, evutil_socket_error_to_string(err));
+		evutil_closesocket(m_SecondarySock);
+		m_SecondarySock = -1;
+		return;
+	}
+
+	m_SecondaryEvent = event_new(cNetworkSingleton::Get().GetEventBase(), m_SecondarySock, EV_READ | EV_PERSIST, RawCallback, this);
+	event_add(m_SecondaryEvent, nullptr);
+}
+
+
+
+
+
+void cUDPEndpointImpl::RawCallback(evutil_socket_t a_Socket, short a_What, void * a_Self)
+{
+	cUDPEndpointImpl * Self = reinterpret_cast<cUDPEndpointImpl *>(a_Self);
+	Self->Callback(a_Socket, a_What);
+}
+
+
+
+
+
+void cUDPEndpointImpl::Callback(evutil_socket_t a_Socket, short a_What)
+{
+	if ((a_What & EV_READ) != 0)
+	{
+		// Receive datagram from the socket:
+		char buf[64 KiB];
+		socklen_t buflen = static_cast<socklen_t>(sizeof(buf));
+		sockaddr_storage sa;
+		socklen_t salen = static_cast<socklen_t>(sizeof(sa));
+		auto len = recvfrom(a_Socket, buf, buflen, 0, reinterpret_cast<sockaddr *>(&sa), &salen);
+		if (len >= 0)
+		{
+			// Convert the remote IP address to a string:
+			char RemoteHost[128];
+			UInt16 RemotePort;
+			switch (sa.ss_family)
+			{
+				case AF_INET:
+				{
+					auto sin = reinterpret_cast<sockaddr_in *>(&sa);
+					evutil_inet_ntop(sa.ss_family, &sin->sin_addr, RemoteHost, sizeof(RemoteHost));
+					RemotePort = ntohs(sin->sin_port);
+					break;
+				}
+				case AF_INET6:
+				{
+					auto sin = reinterpret_cast<sockaddr_in6 *>(&sa);
+					evutil_inet_ntop(sa.ss_family, &sin->sin6_addr, RemoteHost, sizeof(RemoteHost));
+					RemotePort = ntohs(sin->sin6_port);
+					break;
+				}
+				default:
+				{
+					return;
+				}
+			}
+
+			// Call the callback:
+			m_Callbacks.OnReceivedData(buf, static_cast<size_t>(len), RemoteHost, RemotePort);
+		}
+	}
+}
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cNetwork API:
+
+cUDPEndpointPtr cNetwork::CreateUDPEndpoint(UInt16 a_Port, cUDPEndpoint::cCallbacks & a_Callbacks)
+{
+	return std::make_shared<cUDPEndpointImpl>(a_Port, a_Callbacks);
+}
+
+
+
+
diff --git a/src/OSSupport/UDPEndpointImpl.h b/src/OSSupport/UDPEndpointImpl.h
new file mode 100644
index 000000000..75942b0cf
--- /dev/null
+++ b/src/OSSupport/UDPEndpointImpl.h
@@ -0,0 +1,81 @@
+
+// UDPEndpointImpl.h
+
+// Declares the cUDPEndpointImpl class representing an implementation of an endpoint in UDP communication
+
+
+
+
+
+#pragma once
+
+#include "Network.h"
+#include <event2/event.h>
+
+
+
+
+
+// fwd:
+class cUDPEndpointImpl;
+typedef SharedPtr<cUDPEndpointImpl> cUDPEndpointImplPtr;
+
+
+
+
+
+class cUDPEndpointImpl:
+	public cUDPEndpoint
+{
+	typedef cUDPEndpoint super;
+
+public:
+	/** Creates a new instance of the endpoint, with the specified callbacks.
+	Tries to open on the specified port; if it fails, the endpoint is left in the "closed" state.
+	If a_Port is 0, the OS is free to assign any port number it likes to the endpoint. */
+	cUDPEndpointImpl(UInt16 a_Port, cUDPEndpoint::cCallbacks & a_Callbacks);
+
+	// cUDPEndpoint overrides:
+	virtual void Close(void) override;
+	virtual bool IsOpen(void) const override;
+	virtual UInt16 GetPort(void) const override;
+	virtual bool Send(const AString & a_Payload, const AString & a_Host, UInt16 a_Port) override;
+	virtual void EnableBroadcasts(void) override;
+
+protected:
+	/** The local port on which the endpoint is open.
+	If this is zero, it means the endpoint is closed - either opening has failed, or it has been closed explicitly. */
+	UInt16 m_Port;
+
+	/** The primary underlying OS socket. */
+	evutil_socket_t m_MainSock;
+
+	/** True if m_MainSock is in the IPv6 namespace (needs IPv6 addresses for sending). */
+	bool m_IsMainSockIPv6;
+
+	/** The secondary OS socket (if primary doesn't support dualstack). */
+	evutil_socket_t m_SecondarySock;
+
+	/** The LibEvent handle for the primary socket. */
+	event * m_MainEvent;
+
+	/** The LibEvent handle for the secondary socket. */
+	event * m_SecondaryEvent;
+
+
+	/** Creates and opens the socket on the specified port.
+	If a_Port is 0, the OS is free to assign any port number it likes to the endpoint.
+	If the opening fails, the OnError() callback is called and the endpoint is left "closed" (IsOpen() returns false). */
+	void Open(UInt16 a_Port);
+
+	/** The callback that LibEvent calls when an event occurs on one of the sockets.
+	Calls Callback() on a_Self. */
+	static void RawCallback(evutil_socket_t a_Socket, short a_What, void * a_Self);
+
+	/** The callback that is called when an event occurs on one of the sockets. */
+	void Callback(evutil_socket_t a_Socket, short a_What);
+};
+
+
+
+