17 files changed, 1893 insertions, 10 deletions

diff --git a/src/OSSupport/CMakeLists.txt b/src/OSSupport/CMakeLists.txt
index e943ceb18..9424b63da 100644
--- a/src/OSSupport/CMakeLists.txt
+++ b/src/OSSupport/CMakeLists.txt
@@ -10,12 +10,17 @@ SET (SRCS
 	Event.cpp
 	File.cpp
 	GZipFile.cpp
+	HostnameLookup.cpp
+	IPLookup.cpp
 	IsThread.cpp
 	ListenThread.cpp
+	NetworkSingleton.cpp
 	Semaphore.cpp
+	ServerHandleImpl.cpp
 	Socket.cpp
 	SocketThreads.cpp
 	StackTrace.cpp
+	TCPLinkImpl.cpp
 )
 
 SET (HDRS
@@ -24,13 +29,19 @@ SET (HDRS
 	Event.h
 	File.h
 	GZipFile.h
+	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
 )
 
 if(NOT MSVC)
diff --git a/src/OSSupport/CriticalSection.cpp b/src/OSSupport/CriticalSection.cpp
index 13a3e4d9f..5248356c5 100644
--- a/src/OSSupport/CriticalSection.cpp
+++ b/src/OSSupport/CriticalSection.cpp
@@ -1,5 +1,6 @@
 
 #include "Globals.h"  // NOTE: MSVC stupidness requires this to be the same across all modules
+#include "CriticalSection.h"
 
 
 
diff --git a/src/OSSupport/HostnameLookup.cpp b/src/OSSupport/HostnameLookup.cpp
new file mode 100644
index 000000000..3a2997ffd
--- /dev/null
+++ b/src/OSSupport/HostnameLookup.cpp
@@ -0,0 +1,124 @@
+
+// HostnameLookup.cpp
+
+// Implements the cHostnameLookup class representing an in-progress hostname-to-IP lookup
+
+#include "Globals.h"
+#include "HostnameLookup.h"
+#include <event2/dns.h>
+#include "NetworkSingleton.h"
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cHostnameLookup:
+
+cHostnameLookup::cHostnameLookup(cNetwork::cResolveNameCallbacksPtr a_Callbacks):
+	m_Callbacks(a_Callbacks)
+{
+}
+
+
+
+
+
+void cHostnameLookup::Lookup(const AString & a_Hostname)
+{
+	// Store the hostname for the callback:
+	m_Hostname = a_Hostname;
+
+	// Start the lookup:
+	// Note that we don't have to store the LibEvent lookup handle, LibEvent will free it on its own.
+	evutil_addrinfo hints;
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_protocol = IPPROTO_TCP;
+	hints.ai_socktype = SOCK_STREAM;
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_flags = EVUTIL_AI_CANONNAME;
+	evdns_getaddrinfo(cNetworkSingleton::Get().GetDNSBase(), a_Hostname.c_str(), nullptr, &hints, Callback, this);
+}
+
+
+
+
+
+void cHostnameLookup::Callback(int a_ErrCode, evutil_addrinfo * a_Addr, void * a_Self)
+{
+	// Get the Self class:
+	cHostnameLookup * Self = reinterpret_cast<cHostnameLookup *>(a_Self);
+	ASSERT(Self != nullptr);
+
+	// If an error has occurred, notify the error callback:
+	if (a_ErrCode != 0)
+	{
+		Self->m_Callbacks->OnError(a_ErrCode, evutil_socket_error_to_string(a_ErrCode));
+		cNetworkSingleton::Get().RemoveHostnameLookup(Self);
+		return;
+	}
+
+	// Call the success handler for each entry received:
+	bool HasResolved = false;
+	evutil_addrinfo * OrigAddr = a_Addr;
+	for (;a_Addr != nullptr; a_Addr = a_Addr->ai_next)
+	{
+		char IP[128];
+		switch (a_Addr->ai_family)
+		{
+			case AF_INET:  // IPv4
+			{
+				sockaddr_in * sin = reinterpret_cast<sockaddr_in *>(a_Addr->ai_addr);
+				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);
+				evutil_inet_ntop(AF_INET6, &(sin->sin6_addr), IP, sizeof(IP));
+				break;
+			}
+			default:
+			{
+				// Unknown address family, handle as if this entry wasn't received
+				continue;  // for (a_Addr)
+			}
+		}
+		Self->m_Callbacks->OnNameResolved(Self->m_Hostname, IP);
+		HasResolved = true;
+	}  // for (a_Addr)
+
+	// If only unsupported families were reported, call the Error handler:
+	if (!HasResolved)
+	{
+		Self->m_Callbacks->OnError(DNS_ERR_NODATA, "The name does not resolve to any known address.");
+	}
+	else
+	{
+		Self->m_Callbacks->OnFinished();
+	}
+	evutil_freeaddrinfo(OrigAddr);
+	cNetworkSingleton::Get().RemoveHostnameLookup(Self);
+}
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cNetwork API:
+
+bool cNetwork::HostnameToIP(
+	const AString & a_Hostname,
+	cNetwork::cResolveNameCallbacksPtr a_Callbacks
+)
+{
+	auto Lookup = std::make_shared<cHostnameLookup>(a_Callbacks);
+	cNetworkSingleton::Get().AddHostnameLookup(Lookup);
+	Lookup->Lookup(a_Hostname);
+	return true;
+}
+
+
+
+
diff --git a/src/OSSupport/HostnameLookup.h b/src/OSSupport/HostnameLookup.h
new file mode 100644
index 000000000..d69f24707
--- /dev/null
+++ b/src/OSSupport/HostnameLookup.h
@@ -0,0 +1,47 @@
+
+// HostnameLookup.h
+
+// Declares the cHostnameLookup class representing an in-progress hostname-to-IP lookup
+
+// This is an internal header, no-one outside OSSupport should need to include it; use Network.h instead
+
+
+
+
+
+#pragma once
+
+#include "Network.h"
+#include <event2/util.h>
+
+
+
+
+
+/** Holds information about an in-progress Hostname-to-IP lookup. */
+class cHostnameLookup
+{
+public:
+	/** Creates the lookup object. Doesn't start the lookup yet. */
+	cHostnameLookup(cNetwork::cResolveNameCallbacksPtr a_Callbacks);
+
+	/** Starts the lookup. */
+	void Lookup(const AString & a_Hostname);
+
+protected:
+
+	/** The callbacks to call for resolved names / errors. */
+	cNetwork::cResolveNameCallbacksPtr m_Callbacks;
+
+	/** The hostname that was queried (needed for the callbacks). */
+	AString m_Hostname;
+
+	static void Callback(int a_ErrCode, struct evutil_addrinfo * a_Addr, void * a_Self);
+};
+typedef SharedPtr<cHostnameLookup> cHostnameLookupPtr;
+typedef std::vector<cHostnameLookupPtr> cHostnameLookupPtrs;
+
+
+
+
+
diff --git a/src/OSSupport/IPLookup.cpp b/src/OSSupport/IPLookup.cpp
new file mode 100644
index 000000000..8cdc5132d
--- /dev/null
+++ b/src/OSSupport/IPLookup.cpp
@@ -0,0 +1,111 @@
+
+// IPLookup.cpp
+
+// Implements the cIPLookup class representing an IP-to-hostname lookup in progress.
+
+#include "Globals.h"
+#include "IPLookup.h"
+#include <event2/dns.h>
+#include "NetworkSingleton.h"
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cIPLookup:
+
+cIPLookup::cIPLookup(cNetwork::cResolveNameCallbacksPtr a_Callbacks):
+	m_Callbacks(a_Callbacks)
+{
+	ASSERT(a_Callbacks != nullptr);
+}
+
+
+
+
+
+bool cIPLookup::Lookup(const AString & a_IP)
+{
+	// Parse the IP address string into a sockaddr structure:
+	m_IP = a_IP;
+	sockaddr_storage sa;
+	int salen = static_cast<int>(sizeof(sa));
+	memset(&sa, 0, sizeof(sa));
+	if (evutil_parse_sockaddr_port(a_IP.c_str(), reinterpret_cast<sockaddr *>(&sa), &salen) != 0)
+	{
+		LOGD("Failed to parse IP address \"%s\".", a_IP.c_str());
+		return false;
+	}
+
+	// Call the proper resolver based on the address family:
+	// Note that there's no need to store the evdns_request handle returned, LibEvent frees it on its own.
+	switch (sa.ss_family)
+	{
+		case AF_INET:
+		{
+			sockaddr_in * sa4 = reinterpret_cast<sockaddr_in *>(&sa);
+			evdns_base_resolve_reverse(cNetworkSingleton::Get().GetDNSBase(), &(sa4->sin_addr), 0, Callback, this);
+			break;
+		}
+		case AF_INET6:
+		{
+			sockaddr_in6 * sa6 = reinterpret_cast<sockaddr_in6 *>(&sa);
+			evdns_base_resolve_reverse_ipv6(cNetworkSingleton::Get().GetDNSBase(), &(sa6->sin6_addr), 0, Callback, this);
+			break;
+		}
+		default:
+		{
+			LOGWARNING("%s: Unknown address family: %d", __FUNCTION__, sa.ss_family);
+			ASSERT(!"Unknown address family");
+			return false;
+		}
+	}  // switch (address family)
+	return true;
+}
+
+
+
+
+
+void cIPLookup::Callback(int a_Result, char a_Type, int a_Count, int a_Ttl, void * a_Addresses, void * a_Self)
+{
+	// Get the Self class:
+	cIPLookup * Self = reinterpret_cast<cIPLookup *>(a_Self);
+	ASSERT(Self != nullptr);
+
+	// Call the proper callback based on the event received:
+	if ((a_Result != 0) || (a_Addresses == nullptr))
+	{
+		// An error has occurred, notify the error callback:
+		Self->m_Callbacks->OnError(a_Result, evutil_socket_error_to_string(a_Result));
+	}
+	else
+	{
+		// Call the success handler:
+		Self->m_Callbacks->OnNameResolved(*(reinterpret_cast<char **>(a_Addresses)), Self->m_IP);
+		Self->m_Callbacks->OnFinished();
+	}
+	cNetworkSingleton::Get().RemoveIPLookup(Self);
+}
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cNetwork API:
+
+bool cNetwork::IPToHostName(
+	const AString & a_IP,
+	cNetwork::cResolveNameCallbacksPtr a_Callbacks
+)
+{
+	auto res = std::make_shared<cIPLookup>(a_Callbacks);
+	cNetworkSingleton::Get().AddIPLookup(res);
+	return res->Lookup(a_IP);
+}
+
+
+
+
diff --git a/src/OSSupport/IPLookup.h b/src/OSSupport/IPLookup.h
new file mode 100644
index 000000000..af878cbf1
--- /dev/null
+++ b/src/OSSupport/IPLookup.h
@@ -0,0 +1,49 @@
+
+// IPLookup.h
+
+// Declares the cIPLookup class representing an IP-to-hostname lookup in progress.
+
+// This is an internal header, no-one outside OSSupport should need to include it; use Network.h instead
+
+
+
+
+
+#pragma once
+
+#include "Network.h"
+
+
+
+
+
+/** Holds information about an in-progress IP-to-Hostname lookup. */
+class cIPLookup
+{
+public:
+	/** Creates the lookup object. Doesn't start the lookup yet. */
+	cIPLookup(cNetwork::cResolveNameCallbacksPtr a_Callbacks);
+
+	/** Starts the lookup.
+	Returns true if lookup started successfully, false on failure (invalid IP format etc.) */
+	bool Lookup(const AString & a_IP);
+
+protected:
+
+	/** The callbacks to call for resolved names / errors. */
+	cNetwork::cResolveNameCallbacksPtr m_Callbacks;
+
+	/** The IP that was queried (needed for the callbacks). */
+	AString m_IP;
+
+
+	/** Callback that is called by LibEvent when there's an event for the request. */
+	static void Callback(int a_Result, char a_Type, int a_Count, int a_Ttl, void * a_Addresses, void * a_Self);
+};
+typedef SharedPtr<cIPLookup> cIPLookupPtr;
+typedef std::vector<cIPLookupPtr> cIPLookupPtrs;
+
+
+
+
+
diff --git a/src/OSSupport/IsThread.cpp b/src/OSSupport/IsThread.cpp
index 94bed1f56..55e96b622 100644
--- a/src/OSSupport/IsThread.cpp
+++ b/src/OSSupport/IsThread.cpp
@@ -68,11 +68,22 @@ cIsThread::~cIsThread()
 
 
 
+void cIsThread::DoExecute(void)
+{
+	m_evtStart.Wait();
+	Execute();
+}
+
+
+
+
+
 bool cIsThread::Start(void)
 {
 	try
 	{
-		m_Thread = std::thread(&cIsThread::Execute, this);
+		// Initialize the thread:
+		m_Thread = std::thread(&cIsThread::DoExecute, this);
 
 		#if defined (_MSC_VER) && defined(_DEBUG)
 		if (!m_ThreadName.empty())
@@ -81,9 +92,12 @@ bool cIsThread::Start(void)
 		}
 		#endif
 
+		// Notify the thread that initialization is complete and it can run its code safely:
+		m_evtStart.Set();
+
 		return true;
 	}
-	catch (std::system_error & a_Exception)
+	catch (const std::system_error & a_Exception)
 	{
 		LOGERROR("cIsThread::Start error %i: could not construct thread %s; %s", a_Exception.code().value(), m_ThreadName.c_str(), a_Exception.code().message().c_str());
 		return false;
diff --git a/src/OSSupport/IsThread.h b/src/OSSupport/IsThread.h
index 131c6950e..f642c8724 100644
--- a/src/OSSupport/IsThread.h
+++ b/src/OSSupport/IsThread.h
@@ -25,23 +25,28 @@ In the descending class' constructor call the Start() method to start the thread
 class cIsThread
 {
 protected:
-	/// This is the main thread entrypoint
+	/** This is the main thread entrypoint.
+	This function, overloaded by the descendants, is called in the new thread. */
 	virtual void Execute(void) = 0;
 
-	/// The overriden Execute() method should check this value periodically and terminate if this is true
+	/** The overriden Execute() method should check this value periodically and terminate if this is true. */
 	volatile bool m_ShouldTerminate;
 
+private:
+	/** Wrapper for Execute() that waits for the initialization event, to prevent race conditions in thread initialization. */
+	void DoExecute(void);
+
 public:
 	cIsThread(const AString & a_ThreadName);
 	virtual ~cIsThread();
 
-	/// Starts the thread; returns without waiting for the actual start
+	/** Starts the thread; returns without waiting for the actual start. */
 	bool Start(void);
 
-	/// Signals the thread to terminate and waits until it's finished
+	/** Signals the thread to terminate and waits until it's finished. */
 	void Stop(void);
 
-	/// Waits for the thread to finish. Doesn't signalize the ShouldTerminate flag
+	/** Waits for the thread to finish. Doesn't signalize the ShouldTerminate flag. */
 	bool Wait(void);
 
 	/** Returns true if the thread calling this function is the thread contained within this object. */
@@ -50,6 +55,10 @@ public:
 protected:
 	AString m_ThreadName;
 	std::thread m_Thread;
+
+	/** The event that is used to wait with the thread's execution until the thread object is fully initialized.
+	This prevents the IsCurrentThread() call to fail because of a race-condition. */
+	cEvent m_evtStart;
 } ;
 
 
diff --git a/src/OSSupport/Network.h b/src/OSSupport/Network.h
new file mode 100644
index 000000000..cdf6ba0e9
--- /dev/null
+++ b/src/OSSupport/Network.h
@@ -0,0 +1,246 @@
+
+// Network.h
+
+// Declares the classes used for the Network API
+
+
+
+
+
+#pragma once
+
+
+
+
+
+// fwd:
+class cTCPLink;
+typedef SharedPtr<cTCPLink> cTCPLinkPtr;
+typedef std::vector<cTCPLinkPtr> cTCPLinkPtrs;
+class cServerHandle;
+typedef SharedPtr<cServerHandle> cServerHandlePtr;
+typedef std::vector<cServerHandlePtr> cServerHandlePtrs;
+
+
+
+
+
+/** Interface that provides the methods available on a single TCP connection. */
+class cTCPLink
+{
+	friend class cNetwork;
+
+public:
+	class cCallbacks
+	{
+	public:
+		// Force a virtual destructor for all descendants:
+		virtual ~cCallbacks() {}
+
+		/** Called when the cTCPLink for the connection is created.
+		The callback may store the cTCPLink instance for later use, but it should remove it in OnError(), OnRemoteClosed() or right after Close(). */
+		virtual void OnLinkCreated(cTCPLinkPtr a_Link) = 0;
+
+		/** Called when there's data incoming from the remote peer. */
+		virtual void OnReceivedData(const char * a_Data, size_t a_Length) = 0;
+
+		/** Called when the remote end closes the connection.
+		The link is still available for connection information query (IP / port).
+		Sending data on the link is not an error, but the data won't be delivered. */
+		virtual void OnRemoteClosed(void) = 0;
+
+		/** Called when an error is detected on the connection. */
+		virtual void OnError(int a_ErrorCode, const AString & a_ErrorMsg) = 0;
+	};
+	typedef SharedPtr<cCallbacks> cCallbacksPtr;
+
+
+	// Force a virtual destructor for all descendants:
+	virtual ~cTCPLink() {}
+
+	/** Queues the specified data for sending to the remote peer.
+	Returns true on success, false on failure. Note that this success or failure only reports the queue status, not the actual data delivery. */
+	virtual bool Send(const void * a_Data, size_t a_Length) = 0;
+
+	/** Queues the specified data for sending to the remote peer.
+	Returns true on success, false on failure. Note that this success or failure only reports the queue status, not the actual data delivery. */
+	bool Send(const AString & a_Data)
+	{
+		return Send(a_Data.data(), a_Data.size());
+	}
+
+	/** Returns the IP address of the local endpoint of the connection. */
+	virtual AString GetLocalIP(void) const = 0;
+
+	/** Returns the port used by the local endpoint of the connection. */
+	virtual UInt16 GetLocalPort(void) const = 0;
+
+	/** Returns the IP address of the remote endpoint of the connection. */
+	virtual AString GetRemoteIP(void) const = 0;
+
+	/** Returns the port used by the remote endpoint of the connection. */
+	virtual UInt16 GetRemotePort(void) const = 0;
+
+	/** Closes the link gracefully.
+	The link will send any queued outgoing data, then it will send the FIN packet.
+	The link will still receive incoming data from remote until the remote closes the connection. */
+	virtual void Shutdown(void) = 0;
+
+	/** Drops the connection without any more processing.
+	Sends the RST packet, queued outgoing and incoming data is lost. */
+	virtual void Close(void) = 0;
+
+protected:
+	/** Callbacks to be used for the various situations. */
+	cCallbacksPtr m_Callbacks;
+
+
+	/** Creates a new link, with the specified callbacks. */
+	cTCPLink(cCallbacksPtr a_Callbacks):
+		m_Callbacks(a_Callbacks)
+	{
+	}
+};
+
+
+
+
+
+/** Interface that provides the methods available on a listening server socket. */
+class cServerHandle
+{
+	friend class cNetwork;
+public:
+
+	// Force a virtual destructor for all descendants:
+	virtual ~cServerHandle() {}
+
+	/** Stops the server, no more incoming connections will be accepted.
+	All current connections will be shut down (cTCPLink::Shutdown()). */
+	virtual void Close(void) = 0;
+
+	/** Returns true if the server has been started correctly and is currently listening for incoming connections. */
+	virtual bool IsListening(void) const = 0;
+};
+
+
+
+
+
+class cNetwork
+{
+public:
+	/** Callbacks used for connecting to other servers as a client. */
+	class cConnectCallbacks
+	{
+	public:
+		// Force a virtual destructor for all descendants:
+		virtual ~cConnectCallbacks() {}
+
+		/** Called when the Connect call succeeds.
+		Provides the newly created link that can be used for communication. */
+		virtual void OnConnected(cTCPLink & a_Link) = 0;
+
+		/** Called when the Connect call fails. */
+		virtual void OnError(int a_ErrorCode, const AString & a_ErrorMsg) = 0;
+	};
+	typedef SharedPtr<cConnectCallbacks> cConnectCallbacksPtr;
+
+
+	/** Callbacks used when listening for incoming connections as a server. */
+	class cListenCallbacks
+	{
+	public:
+		// Force a virtual destructor for all descendants:
+		virtual ~cListenCallbacks() {}
+
+		/** Called when the TCP server created with Listen() receives a new incoming connection.
+		Returns the link callbacks that the server should use for the newly created link.
+		If a nullptr is returned, the connection is dropped immediately;
+		otherwise a new cTCPLink instance is created and OnAccepted() is called. */
+		virtual cTCPLink::cCallbacksPtr OnIncomingConnection(const AString & a_RemoteIPAddress, UInt16 a_RemotePort) = 0;
+
+		/** Called when the TCP server created with Listen() creates a new link for an incoming connection.
+		Provides the newly created Link that can be used for communication.
+		Called right after a successful OnIncomingConnection(). */
+		virtual void OnAccepted(cTCPLink & a_Link) = 0;
+
+		/** Called when the socket fails to listen on the specified port. */
+		virtual void OnError(int a_ErrorCode, const AString & a_ErrorMsg) = 0;
+	};
+	typedef SharedPtr<cListenCallbacks> cListenCallbacksPtr;
+
+
+	/** Callbacks used when resolving names to IPs. */
+	class cResolveNameCallbacks
+	{
+	public:
+		// Force a virtual destructor for all descendants:
+		virtual ~cResolveNameCallbacks() {}
+
+		/** 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. */
+		virtual void OnNameResolved(const AString & a_Name, const AString & a_IP) = 0;
+
+		/** 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;
+
+		/** Called when all the addresses resolved have been reported via the OnNameResolved() callback.
+		Only called if there was no error reported. */
+		virtual void OnFinished(void) = 0;
+	};
+	typedef SharedPtr<cResolveNameCallbacks> cResolveNameCallbacksPtr;
+
+
+	/** Queues a TCP connection to be made to the specified host.
+	Calls one the connection callbacks (success, error) when the connection is successfully established, or upon failure.
+	The a_LinkCallbacks is passed to the newly created cTCPLink.
+	Returns true if queueing was successful, false on failure to queue.
+	Note that the return value doesn't report the success of the actual connection; the connection is established asynchronously in the background.
+	Implemented in TCPLinkImpl.cpp. */
+	static bool Connect(
+		const AString & a_Host,
+		UInt16 a_Port,
+		cConnectCallbacksPtr a_ConnectCallbacks,
+		cTCPLink::cCallbacksPtr a_LinkCallbacks
+	);
+
+
+	/** Opens up the specified port for incoming connections.
+	Calls an OnAccepted callback for each incoming connection.
+	A cTCPLink with the specified link callbacks is created for each connection.
+	Returns a cServerHandle that can be used to query the operation status and close the server.
+	Implemented in ServerHandleImpl.cpp. */
+	static cServerHandlePtr Listen(
+		UInt16 a_Port,
+		cListenCallbacksPtr a_ListenCallbacks
+	);
+
+
+	/** Queues a DNS query to resolve the specified hostname to IP address.
+	Calls one of the callbacks when the resolving succeeds, or when it fails.
+	Returns true if queueing was successful, false if not.
+	Note that the return value doesn't report the success of the actual lookup; the lookup happens asynchronously on the background.
+	Implemented in HostnameLookup.cpp. */
+	static bool HostnameToIP(
+		const AString & a_Hostname,
+		cResolveNameCallbacksPtr a_Callbacks
+	);
+
+
+	/** Queues a DNS query to resolve the specified IP address to a hostname.
+	Calls one of the callbacks when the resolving succeeds, or when it fails.
+	Returns true if queueing was successful, false if not.
+	Note that the return value doesn't report the success of the actual lookup; the lookup happens asynchronously on the background.
+	Implemented in IPLookup.cpp. */
+	static bool IPToHostName(
+		const AString & a_IP,
+		cResolveNameCallbacksPtr a_Callbacks
+	);
+};
+
+
+
+
diff --git a/src/OSSupport/NetworkSingleton.cpp b/src/OSSupport/NetworkSingleton.cpp
new file mode 100644
index 000000000..92f0604cd
--- /dev/null
+++ b/src/OSSupport/NetworkSingleton.cpp
@@ -0,0 +1,245 @@
+
+// NetworkSingleton.cpp
+
+// Implements 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.
+
+#include "Globals.h"
+#include "NetworkSingleton.h"
+#include <event2/event.h>
+#include <event2/thread.h>
+#include <event2/bufferevent.h>
+#include <event2/dns.h>
+#include <event2/listener.h>
+#include "IPLookup.h"
+#include "HostnameLookup.h"
+
+
+
+
+
+cNetworkSingleton::cNetworkSingleton(void)
+{
+	// Windows: initialize networking:
+	#ifdef _WIN32
+		WSADATA wsaData;
+		memset(&wsaData, 0, sizeof(wsaData));
+		int res = WSAStartup (MAKEWORD(2, 2), &wsaData);
+		if (res != 0)
+		{
+			int err = WSAGetLastError();
+			LOGWARNING("WSAStartup failed: %d, WSAGLE = %d (%s)", res, err, evutil_socket_error_to_string(err));
+			exit(1);
+		}
+	#endif  // _WIN32
+
+	// Initialize LibEvent logging:
+	event_set_log_callback(LogCallback);
+
+	// Initialize threading:
+	#if defined(EVTHREAD_USE_WINDOWS_THREADS_IMPLEMENTED)
+		evthread_use_windows_threads();
+	#elif defined(EVTHREAD_USE_PTHREADS_IMPLEMENTED)
+		evthread_use_pthreads();
+	#else
+		#error No threading implemented for EVTHREAD
+	#endif
+
+	// Create the main event_base:
+	m_EventBase = event_base_new();
+	if (m_EventBase == nullptr)
+	{
+		LOGERROR("Failed to initialize LibEvent. The server will now terminate.");
+		abort();
+	}
+
+	// Create the DNS lookup helper:
+	m_DNSBase = evdns_base_new(m_EventBase, 1);
+	if (m_DNSBase == nullptr)
+	{
+		LOGERROR("Failed to initialize LibEvent's DNS subsystem. The server will now terminate.");
+		abort();
+	}
+
+	// Create the event loop thread:
+	std::thread EventLoopThread(RunEventLoop, this);
+	EventLoopThread.detach();
+}
+
+
+
+
+
+cNetworkSingleton::~cNetworkSingleton()
+{
+	// Wait for the LibEvent event loop to terminate:
+	event_base_loopbreak(m_EventBase);
+	m_EventLoopTerminated.Wait();
+
+	// Remove all objects:
+	{
+		cCSLock Lock(m_CS);
+		m_Connections.clear();
+		m_Servers.clear();
+		m_HostnameLookups.clear();
+		m_IPLookups.clear();
+	}
+
+	// Free the underlying LibEvent objects:
+	evdns_base_free(m_DNSBase, true);
+	event_base_free(m_EventBase);
+
+	libevent_global_shutdown();
+}
+
+
+
+
+
+cNetworkSingleton & cNetworkSingleton::Get(void)
+{
+	static cNetworkSingleton Instance;
+	return Instance;
+}
+
+
+
+
+
+void cNetworkSingleton::LogCallback(int a_Severity, const char * a_Msg)
+{
+	switch (a_Severity)
+	{
+		case _EVENT_LOG_DEBUG: LOGD      ("LibEvent: %s", a_Msg); break;
+		case _EVENT_LOG_MSG:   LOG       ("LibEvent: %s", a_Msg); break;
+		case _EVENT_LOG_WARN:  LOGWARNING("LibEvent: %s", a_Msg); break;
+		case _EVENT_LOG_ERR:   LOGERROR  ("LibEvent: %s", a_Msg); break;
+		default:
+		{
+			LOGWARNING("LibEvent: Unknown log severity (%d): %s", a_Severity, a_Msg);
+			break;
+		}
+	}
+}
+
+
+
+
+
+void cNetworkSingleton::RunEventLoop(cNetworkSingleton * a_Self)
+{
+	event_base_loop(a_Self->m_EventBase, EVLOOP_NO_EXIT_ON_EMPTY);
+	a_Self->m_EventLoopTerminated.Set();
+}
+
+
+
+
+
+void cNetworkSingleton::AddHostnameLookup(cHostnameLookupPtr a_HostnameLookup)
+{
+	cCSLock Lock(m_CS);
+	m_HostnameLookups.push_back(a_HostnameLookup);
+}
+
+
+
+
+
+void cNetworkSingleton::RemoveHostnameLookup(const cHostnameLookup * a_HostnameLookup)
+{
+	cCSLock Lock(m_CS);
+	for (auto itr = m_HostnameLookups.begin(), end = m_HostnameLookups.end(); itr != end; ++itr)
+	{
+		if (itr->get() == a_HostnameLookup)
+		{
+			m_HostnameLookups.erase(itr);
+			return;
+		}
+	}  // for itr - m_HostnameLookups[]
+}
+
+
+
+
+
+void cNetworkSingleton::AddIPLookup(cIPLookupPtr a_IPLookup)
+{
+	cCSLock Lock(m_CS);
+	m_IPLookups.push_back(a_IPLookup);
+}
+
+
+
+
+
+void cNetworkSingleton::RemoveIPLookup(const cIPLookup * a_IPLookup)
+{
+	cCSLock Lock(m_CS);
+	for (auto itr = m_IPLookups.begin(), end = m_IPLookups.end(); itr != end; ++itr)
+	{
+		if (itr->get() == a_IPLookup)
+		{
+			m_IPLookups.erase(itr);
+			return;
+		}
+	}  // for itr - m_IPLookups[]
+}
+
+
+
+
+
+void cNetworkSingleton::AddLink(cTCPLinkImplPtr a_Link)
+{
+	cCSLock Lock(m_CS);
+	m_Connections.push_back(a_Link);
+}
+
+
+
+
+
+void cNetworkSingleton::RemoveLink(const cTCPLinkImpl * a_Link)
+{
+	cCSLock Lock(m_CS);
+	for (auto itr = m_Connections.begin(), end = m_Connections.end(); itr != end; ++itr)
+	{
+		if (itr->get() == a_Link)
+		{
+			m_Connections.erase(itr);
+			return;
+		}
+	}  // for itr - m_Connections[]
+}
+
+
+
+
+
+void cNetworkSingleton::AddServer(cServerHandleImplPtr a_Server)
+{
+	cCSLock Lock(m_CS);
+	m_Servers.push_back(a_Server);
+}
+
+
+
+
+
+void cNetworkSingleton::RemoveServer(const cServerHandleImpl * a_Server)
+{
+	cCSLock Lock(m_CS);
+	for (auto itr = m_Servers.begin(), end = m_Servers.end(); itr != end; ++itr)
+	{
+		if (itr->get() == a_Server)
+		{
+			m_Servers.erase(itr);
+			return;
+		}
+	}  // for itr - m_Servers[]
+}
+
+
+
+
diff --git a/src/OSSupport/NetworkSingleton.h b/src/OSSupport/NetworkSingleton.h
new file mode 100644
index 000000000..1d26fc8f4
--- /dev/null
+++ b/src/OSSupport/NetworkSingleton.h
@@ -0,0 +1,134 @@
+
+// NetworkSingleton.h
+
+// 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
+
+
+
+
+
+#pragma once
+
+#include "Network.h"
+#include "CriticalSection.h"
+#include "Event.h"
+
+
+
+
+
+// fwd:
+struct event_base;
+struct evdns_base;
+class cTCPLinkImpl;
+typedef SharedPtr<cTCPLinkImpl> cTCPLinkImplPtr;
+typedef std::vector<cTCPLinkImplPtr> cTCPLinkImplPtrs;
+class cServerHandleImpl;
+typedef SharedPtr<cServerHandleImpl> cServerHandleImplPtr;
+typedef std::vector<cServerHandleImplPtr> cServerHandleImplPtrs;
+class cHostnameLookup;
+typedef SharedPtr<cHostnameLookup> cHostnameLookupPtr;
+typedef std::vector<cHostnameLookupPtr> cHostnameLookupPtrs;
+class cIPLookup;
+typedef SharedPtr<cIPLookup> cIPLookupPtr;
+typedef std::vector<cIPLookupPtr> cIPLookupPtrs;
+
+
+
+
+
+class cNetworkSingleton
+{
+public:
+	~cNetworkSingleton();
+
+	/** Returns the singleton instance of this class */
+	static cNetworkSingleton & Get(void);
+
+	/** Returns the main LibEvent handle for event registering. */
+	event_base * GetEventBase(void) { return m_EventBase; }
+
+	/** Returns the LibEvent handle for DNS lookups. */
+	evdns_base * GetDNSBase(void) { return m_DNSBase; }
+
+	/** Adds the specified hostname lookup to m_HostnameLookups.
+	Used by the underlying lookup implementation when a new lookup is initiated. */
+	void AddHostnameLookup(cHostnameLookupPtr a_HostnameLookup);
+
+	/** Removes the specified hostname lookup from m_HostnameLookups.
+	Used by the underlying lookup implementation when the lookup is finished. */
+	void RemoveHostnameLookup(const cHostnameLookup * a_HostnameLookup);
+
+	/** Adds the specified IP lookup to M_IPLookups.
+	Used by the underlying lookup implementation when a new lookup is initiated. */
+	void AddIPLookup(cIPLookupPtr a_IPLookup);
+
+	/** Removes the specified IP lookup from m_IPLookups.
+	Used by the underlying lookup implementation when the lookup is finished. */
+	void RemoveIPLookup(const cIPLookup * a_IPLookup);
+
+	/** Adds the specified link to m_Connections.
+	Used by the underlying link implementation when a new link is created. */
+	void AddLink(cTCPLinkImplPtr a_Link);
+
+	/** Removes the specified link from m_Connections.
+	Used by the underlying link implementation when the link is closed / errored. */
+	void RemoveLink(const cTCPLinkImpl * a_Link);
+
+	/** Adds the specified link to m_Servers.
+	Used by the underlying server handle implementation when a new listening server is created.
+	Only servers that succeed in listening are added. */
+	void AddServer(cServerHandleImplPtr a_Server);
+
+	/** Removes the specified server from m_Servers.
+	Used by the underlying server handle implementation when the server is closed. */
+	void RemoveServer(const cServerHandleImpl * a_Server);
+
+protected:
+
+	/** The main LibEvent container for driving the event loop. */
+	event_base * m_EventBase;
+
+	/** The LibEvent handle for doing DNS lookups. */
+	evdns_base * m_DNSBase;
+
+	/** Container for all client connections, including ones with pending-connect. */
+	cTCPLinkImplPtrs m_Connections;
+
+	/** Container for all servers that are currently active. */
+	cServerHandleImplPtrs m_Servers;
+
+	/** Container for all pending hostname lookups. */
+	cHostnameLookupPtrs m_HostnameLookups;
+
+	/** Container for all pending IP lookups. */
+	cIPLookupPtrs m_IPLookups;
+
+	/** Mutex protecting all containers against multithreaded access. */
+	cCriticalSection m_CS;
+
+	/** Event that gets signalled when the event loop terminates. */
+	cEvent m_EventLoopTerminated;
+
+
+	/** Initializes the LibEvent internals. */
+	cNetworkSingleton(void);
+
+	/** Converts LibEvent-generated log events into log messages in MCS log. */
+	static void LogCallback(int a_Severity, const char * a_Msg);
+
+	/** Implements the thread that runs LibEvent's event dispatcher loop. */
+	static void RunEventLoop(cNetworkSingleton * a_Self);
+};
+
+
+
+
+
+
+
+
+
diff --git a/src/OSSupport/Queue.h b/src/OSSupport/Queue.h
index 82f221453..afbde1b0d 100644
--- a/src/OSSupport/Queue.h
+++ b/src/OSSupport/Queue.h
@@ -86,7 +86,7 @@ public:
 	bool TryDequeueItem(ItemType & item)
 	{
 		cCSLock Lock(m_CS);
-		if (m_Contents.size() == 0)
+		if (m_Contents.empty())
 		{
 			return false;
 		}
@@ -101,7 +101,7 @@ public:
 	ItemType DequeueItem(void)
 	{
 		cCSLock Lock(m_CS);
-		while (m_Contents.size() == 0)
+		while (m_Contents.empty())
 		{
 			cCSUnlock Unlock(Lock);
 			m_evtAdded.Wait();
diff --git a/src/OSSupport/ServerHandleImpl.cpp b/src/OSSupport/ServerHandleImpl.cpp
new file mode 100644
index 000000000..ba38dbf2e
--- /dev/null
+++ b/src/OSSupport/ServerHandleImpl.cpp
@@ -0,0 +1,334 @@
+
+// ServerHandleImpl.cpp
+
+// Implements the cServerHandleImpl class implementing the TCP server functionality
+
+#include "Globals.h"
+#include "ServerHandleImpl.h"
+#include "TCPLinkImpl.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
+}
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cServerHandleImpl:
+
+cServerHandleImpl::cServerHandleImpl(cNetwork::cListenCallbacksPtr a_ListenCallbacks):
+	m_ListenCallbacks(a_ListenCallbacks),
+	m_ConnListener(nullptr),
+	m_SecondaryConnListener(nullptr),
+	m_IsListening(false),
+	m_ErrorCode(0)
+{
+}
+
+
+
+
+
+cServerHandleImpl::~cServerHandleImpl()
+{
+	if (m_ConnListener != nullptr)
+	{
+		evconnlistener_free(m_ConnListener);
+	}
+	if (m_SecondaryConnListener != nullptr)
+	{
+		evconnlistener_free(m_SecondaryConnListener);
+	}
+}
+
+
+
+
+
+void cServerHandleImpl::Close(void)
+{
+	// Stop the listener sockets:
+	evconnlistener_disable(m_ConnListener);
+	if (m_SecondaryConnListener != nullptr)
+	{
+		evconnlistener_disable(m_SecondaryConnListener);
+	}
+	m_IsListening = false;
+
+	// Shutdown all connections:
+	cTCPLinkImplPtrs Conns;
+	{
+		cCSLock Lock(m_CS);
+		std::swap(Conns, m_Connections);
+	}
+	for (auto conn: Conns)
+	{
+		conn->Shutdown();
+	}
+
+	// Remove the ptr to self, so that the object may be freed:
+	m_SelfPtr.reset();
+}
+
+
+
+
+
+cServerHandleImplPtr cServerHandleImpl::Listen(
+	UInt16 a_Port,
+	cNetwork::cListenCallbacksPtr a_ListenCallbacks
+)
+{
+	cServerHandleImplPtr res = cServerHandleImplPtr{new cServerHandleImpl(a_ListenCallbacks)};
+	res->m_SelfPtr = res;
+	if (res->Listen(a_Port))
+	{
+		cNetworkSingleton::Get().AddServer(res);
+	}
+	else
+	{
+		a_ListenCallbacks->OnError(res->m_ErrorCode, res->m_ErrorMsg);
+		res->m_SelfPtr.reset();
+	}
+	return res;
+}
+
+
+
+
+
+bool cServerHandleImpl::Listen(UInt16 a_Port)
+{
+	// 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;
+	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:
+		err = EVUTIL_SOCKET_ERROR();
+		LOGD("Failed to create IPv6 MainSock: %d (%s)", err, evutil_socket_error_to_string(err));
+		MainSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+		if (!IsValidSocket(MainSock))
+		{
+			m_ErrorCode = EVUTIL_SOCKET_ERROR();
+			Printf(m_ErrorMsg, "Cannot create socket for port %d: %s", a_Port, evutil_socket_error_to_string(m_ErrorCode));
+			return false;
+		}
+
+		// 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(MainSock, reinterpret_cast<const sockaddr *>(&name), sizeof(name)) != 0)
+		{
+			m_ErrorCode = EVUTIL_SOCKET_ERROR();
+			Printf(m_ErrorMsg, "Cannot bind IPv4 socket to port %d: %s", a_Port, evutil_socket_error_to_string(m_ErrorCode));
+			evutil_closesocket(MainSock);
+			return false;
+		}
+	}
+	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(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
+
+		// 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(MainSock, reinterpret_cast<const sockaddr *>(&name), sizeof(name)) != 0)
+		{
+			m_ErrorCode = EVUTIL_SOCKET_ERROR();
+			Printf(m_ErrorMsg, "Cannot bind IPv6 socket to port %d: %d (%s)", a_Port, m_ErrorCode, evutil_socket_error_to_string(m_ErrorCode));
+			evutil_closesocket(MainSock);
+			return false;
+		}
+	}
+	if (evutil_make_socket_nonblocking(MainSock) != 0)
+	{
+		m_ErrorCode = EVUTIL_SOCKET_ERROR();
+		Printf(m_ErrorMsg, "Cannot make socket on port %d non-blocking: %d (%s)", a_Port, m_ErrorCode, evutil_socket_error_to_string(m_ErrorCode));
+		evutil_closesocket(MainSock);
+		return false;
+	}
+	if (listen(MainSock, 0) != 0)
+	{
+		m_ErrorCode = EVUTIL_SOCKET_ERROR();
+		Printf(m_ErrorMsg, "Cannot listen on port %d: %d (%s)", a_Port, m_ErrorCode, evutil_socket_error_to_string(m_ErrorCode));
+		evutil_closesocket(MainSock);
+		return false;
+	}
+	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;
+	}
+
+	// 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();
+		LOGD("socket(AF_INET, ...) failed for secondary socket: %d, %s", err, evutil_socket_error_to_string(err));
+		return true;  // Report as success, the primary socket is working
+	}
+
+	// Make the secondary socket nonblocking:
+	if (evutil_make_socket_nonblocking(SecondSock) != 0)
+	{
+		err = EVUTIL_SOCKET_ERROR();
+		LOGD("evutil_make_socket_nonblocking() failed for secondary socket: %d, %s", err, evutil_socket_error_to_string(err));
+		evutil_closesocket(SecondSock);
+		return true;  // Report as success, the primary socket is working
+	}
+
+	// Bind to all IPv4 interfaces:
+	sockaddr_in name;
+	memset(&name, 0, sizeof(name));
+	name.sin_family = AF_INET;
+	name.sin_port = ntohs(a_Port);
+	if (bind(SecondSock, reinterpret_cast<const sockaddr *>(&name), sizeof(name)) != 0)
+	{
+		err = EVUTIL_SOCKET_ERROR();
+		LOGD("Cannot bind secondary socket to 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
+	}
+
+	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));
+		evutil_closesocket(SecondSock);
+		return true;  // Report as success, the primary socket is working
+	}
+
+	m_SecondaryConnListener = evconnlistener_new(cNetworkSingleton::Get().GetEventBase(), Callback, this, LEV_OPT_CLOSE_ON_FREE | LEV_OPT_REUSEABLE, 0, SecondSock);
+	return true;
+}
+
+
+
+
+
+void cServerHandleImpl::Callback(evconnlistener * a_Listener, evutil_socket_t a_Socket, sockaddr * a_Addr, int a_Len, void * a_Self)
+{
+	// Cast to true self:
+	cServerHandleImpl * Self = reinterpret_cast<cServerHandleImpl *>(a_Self);
+	ASSERT(Self != nullptr);
+	ASSERT(Self->m_SelfPtr != nullptr);
+
+	// 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);
+			Port = ntohs(sin->sin_port);
+			break;
+		}
+		case AF_INET6:
+		{
+			sockaddr_in6 * sin6 = reinterpret_cast<sockaddr_in6 *>(a_Addr);
+			Port = ntohs(sin6->sin6_port);
+			break;
+		}
+	}
+
+	// Call the OnIncomingConnection callback to get the link callbacks to use:
+	cTCPLink::cCallbacksPtr LinkCallbacks = Self->m_ListenCallbacks->OnIncomingConnection(IPAddress, Port);
+	if (LinkCallbacks == nullptr)
+	{
+		// Drop the connection:
+		evutil_closesocket(a_Socket);
+		return;
+	}
+
+	// Create a new cTCPLink for the incoming connection:
+	cTCPLinkImplPtr Link = std::make_shared<cTCPLinkImpl>(a_Socket, LinkCallbacks, Self->m_SelfPtr, a_Addr, static_cast<socklen_t>(a_Len));
+	{
+		cCSLock Lock(Self->m_CS);
+		Self->m_Connections.push_back(Link);
+	}  // Lock(m_CS)
+	LinkCallbacks->OnLinkCreated(Link);
+	Link->Enable(Link);
+
+	// Call the OnAccepted callback:
+	Self->m_ListenCallbacks->OnAccepted(*Link);
+}
+
+
+
+
+
+void cServerHandleImpl::RemoveLink(const cTCPLinkImpl * a_Link)
+{
+	cCSLock Lock(m_CS);
+	for (auto itr = m_Connections.begin(), end = m_Connections.end(); itr != end; ++itr)
+	{
+		if (itr->get() == a_Link)
+		{
+			m_Connections.erase(itr);
+			return;
+		}
+	}  // for itr - m_Connections[]
+}
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cNetwork API:
+
+cServerHandlePtr cNetwork::Listen(
+	UInt16 a_Port,
+	cNetwork::cListenCallbacksPtr a_ListenCallbacks
+)
+{
+	return cServerHandleImpl::Listen(a_Port, a_ListenCallbacks);
+}
+
+
+
+
+
diff --git a/src/OSSupport/ServerHandleImpl.h b/src/OSSupport/ServerHandleImpl.h
new file mode 100644
index 000000000..dbb18fc6d
--- /dev/null
+++ b/src/OSSupport/ServerHandleImpl.h
@@ -0,0 +1,105 @@
+
+// ServerHandleImpl.h
+
+// Declares the cServerHandleImpl class implementing the TCP server functionality
+
+// This is an internal header, no-one outside OSSupport should need to include it; use Network.h instead
+
+
+
+
+
+#pragma once
+
+#include "Network.h"
+#include <event2/listener.h>
+#include "CriticalSection.h"
+
+
+
+
+
+// fwd:
+class cTCPLinkImpl;
+typedef SharedPtr<cTCPLinkImpl> cTCPLinkImplPtr;
+typedef std::vector<cTCPLinkImplPtr> cTCPLinkImplPtrs;
+class cServerHandleImpl;
+typedef SharedPtr<cServerHandleImpl> cServerHandleImplPtr;
+typedef std::vector<cServerHandleImplPtr> cServerHandleImplPtrs;
+
+
+
+
+
+class cServerHandleImpl:
+	public cServerHandle
+{
+	typedef cServerHandle super;
+	friend class cTCPLinkImpl;
+
+public:
+	/** Closes the server, dropping all the connections. */
+	~cServerHandleImpl();
+
+	/** Creates a new server instance listening on the specified port.
+	Both IPv4 and IPv6 interfaces are used, if possible.
+	Always returns a server instance; in the event of a failure, the instance holds the error details. Use IsListening() to query success. */
+	static cServerHandleImplPtr Listen(
+		UInt16 a_Port,
+		cNetwork::cListenCallbacksPtr a_ListenCallbacks
+	);
+
+	// cServerHandle overrides:
+	virtual void Close(void) override;
+	virtual bool IsListening(void) const override { return m_IsListening; }
+
+protected:
+	/** The callbacks used to notify about incoming connections. */
+	cNetwork::cListenCallbacksPtr m_ListenCallbacks;
+
+	/** The LibEvent handle representing the main listening socket. */
+	evconnlistener * m_ConnListener;
+
+	/** The LibEvent handle representing the secondary listening socket (only when side-by-side listening is needed, such as WinXP). */
+	evconnlistener * m_SecondaryConnListener;
+
+	/** Set to true when the server is initialized successfully and is listening for incoming connections. */
+	bool m_IsListening;
+
+	/** Container for all currently active connections on this server. */
+	cTCPLinkImplPtrs m_Connections;
+
+	/** Mutex protecting m_Connections againt multithreaded access. */
+	cCriticalSection m_CS;
+
+	/** Contains the error code for the failure to listen. Only valid for non-listening instances. */
+	int m_ErrorCode;
+
+	/** Contains the error message for the failure to listen. Only valid for non-listening instances. */
+	AString m_ErrorMsg;
+
+	/** The SharedPtr to self, so that it can be passed to created links. */
+	cServerHandleImplPtr m_SelfPtr;
+
+
+
+	/** Creates a new instance with the specified callbacks.
+	Initializes the internals, but doesn't start listening yet. */
+	cServerHandleImpl(cNetwork::cListenCallbacksPtr a_ListenCallbacks);
+
+	/** Starts listening on the specified port.
+	Returns true if successful, false on failure. On failure, sets m_ErrorCode and m_ErrorMsg. */
+	bool Listen(UInt16 a_Port);
+
+	/** The callback called by LibEvent upon incoming connection. */
+	static void Callback(evconnlistener * a_Listener, evutil_socket_t a_Socket, sockaddr * a_Addr, int a_Len, void * a_Self);
+
+	/** Removes the specified link from m_Connections.
+	Called by cTCPLinkImpl when the link is terminated. */
+	void RemoveLink(const cTCPLinkImpl * a_Link);
+};
+
+
+
+
+
diff --git a/src/OSSupport/StackTrace.cpp b/src/OSSupport/StackTrace.cpp
index a56568457..015a53ba0 100644
--- a/src/OSSupport/StackTrace.cpp
+++ b/src/OSSupport/StackTrace.cpp
@@ -34,7 +34,7 @@ void PrintStackTrace(void)
 		// Use the backtrace() function to get and output the stackTrace:
 		// Code adapted from http://stackoverflow.com/questions/77005/how-to-generate-a-stacktrace-when-my-gcc-c-app-crashes
 		void * stackTrace[30];
-		size_t numItems = backtrace(stackTrace, ARRAYCOUNT(stackTrace));
+		int numItems = backtrace(stackTrace, ARRAYCOUNT(stackTrace));
 		backtrace_symbols_fd(stackTrace, numItems, STDERR_FILENO);
 	#endif
 }
diff --git a/src/OSSupport/TCPLinkImpl.cpp b/src/OSSupport/TCPLinkImpl.cpp
new file mode 100644
index 000000000..b4cefa60c
--- /dev/null
+++ b/src/OSSupport/TCPLinkImpl.cpp
@@ -0,0 +1,331 @@
+
+// TCPLinkImpl.cpp
+
+// Implements the cTCPLinkImpl class implementing the TCP link functionality
+
+#include "Globals.h"
+#include "TCPLinkImpl.h"
+#include "NetworkSingleton.h"
+#include "ServerHandleImpl.h"
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cTCPLinkImpl:
+
+cTCPLinkImpl::cTCPLinkImpl(cTCPLink::cCallbacksPtr a_LinkCallbacks):
+	super(a_LinkCallbacks),
+	m_BufferEvent(bufferevent_socket_new(cNetworkSingleton::Get().GetEventBase(), -1, BEV_OPT_CLOSE_ON_FREE))
+{
+}
+
+
+
+
+
+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)
+{
+	// Update the endpoint addresses:
+	UpdateLocalAddress();
+	UpdateAddress(a_Address, a_AddrLen, m_RemoteIP, m_RemotePort);
+}
+
+
+
+
+
+cTCPLinkImpl::~cTCPLinkImpl()
+{
+	bufferevent_free(m_BufferEvent);
+}
+
+
+
+
+
+cTCPLinkImplPtr cTCPLinkImpl::Connect(const AString & a_Host, UInt16 a_Port, cTCPLink::cCallbacksPtr a_LinkCallbacks, cNetwork::cConnectCallbacksPtr a_ConnectCallbacks)
+{
+	ASSERT(a_LinkCallbacks != nullptr);
+	ASSERT(a_ConnectCallbacks != nullptr);
+
+	// Create a new link:
+	cTCPLinkImplPtr res{new cTCPLinkImpl(a_LinkCallbacks)};  // Cannot use std::make_shared here, constructor is not accessible
+	res->m_ConnectCallbacks = a_ConnectCallbacks;
+	cNetworkSingleton::Get().AddLink(res);
+	res->m_Callbacks->OnLinkCreated(res);
+	res->Enable(res);
+
+	// If a_Host is an IP address, schedule a connection immediately:
+	sockaddr_storage sa;
+	int salen = static_cast<int>(sizeof(sa));
+	if (evutil_parse_sockaddr_port(a_Host.c_str(), reinterpret_cast<sockaddr *>(&sa), &salen) == 0)
+	{
+		// Insert the correct port:
+		if (sa.ss_family == AF_INET6)
+		{
+			reinterpret_cast<sockaddr_in6 *>(&sa)->sin6_port = htons(a_Port);
+		}
+		else
+		{
+			reinterpret_cast<sockaddr_in *>(&sa)->sin_port = htons(a_Port);
+		}
+
+		// Queue the connect request:
+		if (bufferevent_socket_connect(res->m_BufferEvent, reinterpret_cast<sockaddr *>(&sa), salen) == 0)
+		{
+			// Success
+			return res;
+		}
+		// Failure
+		cNetworkSingleton::Get().RemoveLink(res.get());
+		return nullptr;
+	}
+
+	// a_Host is a hostname, connect after a lookup:
+	if (bufferevent_socket_connect_hostname(res->m_BufferEvent, cNetworkSingleton::Get().GetDNSBase(), AF_UNSPEC, a_Host.c_str(), a_Port) == 0)
+	{
+		// Success
+		return res;
+	}
+	// Failure
+	cNetworkSingleton::Get().RemoveLink(res.get());
+	return nullptr;
+}
+
+
+
+
+
+void cTCPLinkImpl::Enable(cTCPLinkImplPtr a_Self)
+{
+	// Take hold of a shared copy of self, to keep as long as the callbacks are coming:
+	m_Self = a_Self;
+
+	// Set the LibEvent callbacks and enable processing:
+	bufferevent_setcb(m_BufferEvent, ReadCallback, nullptr, EventCallback, this);
+	bufferevent_enable(m_BufferEvent, EV_READ | EV_WRITE);
+}
+
+
+
+
+
+bool cTCPLinkImpl::Send(const void * a_Data, size_t a_Length)
+{
+	return (bufferevent_write(m_BufferEvent, a_Data, a_Length) == 0);
+}
+
+
+
+
+
+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);
+}
+
+
+
+
+
+void cTCPLinkImpl::Close(void)
+{
+	// Disable all events on the socket, but keep it alive:
+	bufferevent_disable(m_BufferEvent, EV_READ | EV_WRITE);
+	if (m_Server == nullptr)
+	{
+		cNetworkSingleton::Get().RemoveLink(this);
+	}
+	else
+	{
+		m_Server->RemoveLink(this);
+	}
+	m_Self.reset();
+}
+
+
+
+
+
+
+void cTCPLinkImpl::ReadCallback(bufferevent * a_BufferEvent, void * a_Self)
+{
+	ASSERT(a_Self != nullptr);
+	cTCPLinkImpl * Self = static_cast<cTCPLinkImpl *>(a_Self);
+	ASSERT(Self->m_Callbacks != nullptr);
+
+	// Read all the incoming data, in 1024-byte chunks:
+	char data[1024];
+	size_t length;
+	while ((length = bufferevent_read(a_BufferEvent, data, sizeof(data))) > 0)
+	{
+		Self->m_Callbacks->OnReceivedData(data, length);
+	}
+}
+
+
+
+
+
+void cTCPLinkImpl::EventCallback(bufferevent * a_BufferEvent, short a_What, void * a_Self)
+{
+	ASSERT(a_Self != nullptr);
+	cTCPLinkImplPtr Self = static_cast<cTCPLinkImpl *>(a_Self)->m_Self;
+
+	// If an error is reported, call the error callback:
+	if (a_What & BEV_EVENT_ERROR)
+	{
+		// Choose the proper callback to call based on whether we were waiting for connection or not:
+		int err = EVUTIL_SOCKET_ERROR();
+		if (Self->m_ConnectCallbacks != nullptr)
+		{
+			if (err == 0)
+			{
+				// This could be a DNS failure
+				err = bufferevent_socket_get_dns_error(a_BufferEvent);
+			}
+			Self->m_ConnectCallbacks->OnError(err, evutil_socket_error_to_string(err));
+		}
+		else
+		{
+			Self->m_Callbacks->OnError(err, evutil_socket_error_to_string(err));
+			if (Self->m_Server == nullptr)
+			{
+				cNetworkSingleton::Get().RemoveLink(Self.get());
+			}
+			else
+			{
+				Self->m_Server->RemoveLink(Self.get());
+			}
+		}
+		Self->m_Self.reset();
+		return;
+	}
+
+	// Pending connection succeeded, call the connection callback:
+	if (a_What & BEV_EVENT_CONNECTED)
+	{
+		if (Self->m_ConnectCallbacks != nullptr)
+		{
+			Self->m_ConnectCallbacks->OnConnected(*Self);
+			// Reset the connect callbacks so that later errors get reported through the link callbacks:
+			Self->m_ConnectCallbacks.reset();
+			return;
+		}
+		Self->UpdateLocalAddress();
+		Self->UpdateRemoteAddress();
+	}
+
+	// If the connection has been closed, call the link callback and remove the connection:
+	if (a_What & BEV_EVENT_EOF)
+	{
+		Self->m_Callbacks->OnRemoteClosed();
+		if (Self->m_Server != nullptr)
+		{
+			Self->m_Server->RemoveLink(Self.get());
+		}
+		else
+		{
+			cNetworkSingleton::Get().RemoveLink(Self.get());
+		}
+		Self->m_Self.reset();
+		return;
+	}
+	
+	// Unknown event, report it:
+	LOGWARNING("cTCPLinkImpl: Unhandled LibEvent event %d (0x%x)", a_What, a_What);
+	ASSERT(!"cTCPLinkImpl: Unhandled LibEvent event");
+}
+
+
+
+
+
+void cTCPLinkImpl::UpdateAddress(const sockaddr * a_Address, socklen_t a_AddrLen, AString & a_IP, UInt16 & a_Port)
+{
+	// Based on the family specified in the address, use the correct datastructure to convert to IP string:
+	char IP[128];
+	switch (a_Address->sa_family)
+	{
+		case AF_INET:  // IPv4:
+		{
+			const sockaddr_in * sin = reinterpret_cast<const sockaddr_in *>(a_Address);
+			evutil_inet_ntop(AF_INET, &(sin->sin_addr), IP, sizeof(IP));
+			a_Port = ntohs(sin->sin_port);
+			break;
+		}
+		case AF_INET6:  // IPv6
+		{
+			const sockaddr_in6 * sin = reinterpret_cast<const sockaddr_in6 *>(a_Address);
+			evutil_inet_ntop(AF_INET6, &(sin->sin6_addr), IP, sizeof(IP));
+			a_Port = ntohs(sin->sin6_port);
+			break;
+		}
+
+		default:
+		{
+			LOGWARNING("%s: Unknown socket address family: %d", __FUNCTION__, a_Address->sa_family);
+			ASSERT(!"Unknown socket address family");
+			break;
+		}
+	}
+	a_IP.assign(IP);
+}
+
+
+
+
+
+void cTCPLinkImpl::UpdateLocalAddress(void)
+{
+	sockaddr_storage sa;
+	socklen_t salen = static_cast<socklen_t>(sizeof(sa));
+	getsockname(bufferevent_getfd(m_BufferEvent), reinterpret_cast<sockaddr *>(&sa), &salen);
+	UpdateAddress(reinterpret_cast<const sockaddr *>(&sa), salen, m_LocalIP, m_LocalPort);
+}
+
+
+
+
+
+void cTCPLinkImpl::UpdateRemoteAddress(void)
+{
+	sockaddr_storage sa;
+	socklen_t salen = static_cast<socklen_t>(sizeof(sa));
+	getpeername(bufferevent_getfd(m_BufferEvent), reinterpret_cast<sockaddr *>(&sa), &salen);
+	UpdateAddress(reinterpret_cast<const sockaddr *>(&sa), salen, m_RemoteIP, m_RemotePort);
+}
+
+
+
+
+
+////////////////////////////////////////////////////////////////////////////////
+// cNetwork API:
+
+bool cNetwork::Connect(
+	const AString & a_Host,
+	UInt16 a_Port,
+	cNetwork::cConnectCallbacksPtr a_ConnectCallbacks,
+	cTCPLink::cCallbacksPtr a_LinkCallbacks
+)
+{
+	// Add a connection request to the queue:
+	cTCPLinkImplPtr Conn = cTCPLinkImpl::Connect(a_Host, a_Port, a_LinkCallbacks, a_ConnectCallbacks);
+	return (Conn != nullptr);
+}
+
+
+
+
+
diff --git a/src/OSSupport/TCPLinkImpl.h b/src/OSSupport/TCPLinkImpl.h
new file mode 100644
index 000000000..735e8ed9d
--- /dev/null
+++ b/src/OSSupport/TCPLinkImpl.h
@@ -0,0 +1,122 @@
+
+// TCPLinkImpl.h
+
+// Declares the cTCPLinkImpl class implementing the TCP link functionality
+
+// This is an internal header, no-one outside OSSupport should need to include it; use Network.h instead
+
+
+
+
+
+#pragma once
+
+#include "Network.h"
+#include <event2/event.h>
+#include <event2/bufferevent.h>
+
+
+
+
+
+// fwd:
+class cServerHandleImpl;
+typedef SharedPtr<cServerHandleImpl> cServerHandleImplPtr;
+class cTCPLinkImpl;
+typedef SharedPtr<cTCPLinkImpl> cTCPLinkImplPtr;
+typedef std::vector<cTCPLinkImplPtr> cTCPLinkImplPtrs;
+
+
+
+
+
+class cTCPLinkImpl:
+	public cTCPLink
+{
+	typedef cTCPLink super;
+
+public:
+	/** Creates a new link based on the given socket.
+	Used for connections accepted in a server using cNetwork::Listen().
+	a_Address and a_AddrLen describe the remote peer that has connected.
+	The link is created disabled, you need to call Enable() to start the regular communication. */
+	cTCPLinkImpl(evutil_socket_t a_Socket, cCallbacksPtr a_LinkCallbacks, cServerHandleImplPtr a_Server, const sockaddr * a_Address, socklen_t a_AddrLen);
+
+	/** Destroys the LibEvent handle representing the link. */
+	~cTCPLinkImpl();
+
+	/** Queues a connection request to the specified host.
+	a_ConnectCallbacks must be valid.
+	Returns a link that has the connection request queued, or NULL for failure. */
+	static cTCPLinkImplPtr Connect(const AString & a_Host, UInt16 a_Port, cTCPLink::cCallbacksPtr a_LinkCallbacks, cNetwork::cConnectCallbacksPtr a_ConnectCallbacks);
+
+	/** Enables communication over the link.
+	Links are created with communication disabled, so that creation callbacks can be called first.
+	This function then enables the regular communication to be reported.
+	The a_Self parameter is used so that the socket can keep itself alive as long as the callbacks are coming. */
+	void Enable(cTCPLinkImplPtr a_Self);
+
+	// cTCPLink overrides:
+	virtual bool Send(const void * a_Data, size_t a_Length) override;
+	virtual AString GetLocalIP(void) const override { return m_LocalIP; }
+	virtual UInt16 GetLocalPort(void) const override { return m_LocalPort; }
+	virtual AString GetRemoteIP(void) const override { return m_RemoteIP; }
+	virtual UInt16 GetRemotePort(void) const override { return m_RemotePort; }
+	virtual void Shutdown(void) override;
+	virtual void Close(void) override;
+
+protected:
+
+	/** Callbacks to call when the connection is established.
+	May be NULL if not used. Only used for outgoing connections (cNetwork::Connect()). */
+	cNetwork::cConnectCallbacksPtr m_ConnectCallbacks;
+
+	/** The LibEvent handle representing this connection. */
+	bufferevent * m_BufferEvent;
+
+	/** The server handle that has created this link.
+	Only valid for incoming connections, nullptr for outgoing connections. */
+	cServerHandleImplPtr m_Server;
+
+	/** The IP address of the local endpoint. Valid only after the socket has been connected. */
+	AString m_LocalIP;
+
+	/** The port of the local endpoint. Valid only after the socket has been connected. */
+	UInt16 m_LocalPort;
+
+	/** The IP address of the remote endpoint. Valid only after the socket has been connected. */
+	AString m_RemoteIP;
+
+	/** The port of the remote endpoint. Valid only after the socket has been connected. */
+	UInt16 m_RemotePort;
+
+	/** SharedPtr to self, used to keep this object alive as long as the callbacks are coming.
+	Initialized in Enable(), cleared in Close() and EventCallback(RemoteClosed). */
+	cTCPLinkImplPtr m_Self;
+
+
+	/** Creates a new link to be queued to connect to a specified host:port.
+	Used for outgoing connections created using cNetwork::Connect().
+	To be used only by the Connect() factory function.
+	The link is created disabled, you need to call Enable() to start the regular communication. */
+	cTCPLinkImpl(const cCallbacksPtr a_LinkCallbacks);
+
+	/** 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 there's a non-data-related event on the socket. */
+	static void EventCallback(bufferevent * a_BufferEvent, short a_What, void * a_Self);
+
+	/** Sets a_IP and a_Port to values read from a_Address, based on the correct address family. */
+	static void UpdateAddress(const sockaddr * a_Address, socklen_t a_AddrLen, AString & a_IP, UInt16 & a_Port);
+
+	/** Updates m_LocalIP and m_LocalPort based on the metadata read from the socket. */
+	void UpdateLocalAddress(void);
+
+	/** Updates m_RemoteIP and m_RemotePort based on the metadata read from the socket. */
+	void UpdateRemoteAddress(void);
+};
+
+
+
+