// Implements the connection logic for the socket server. // After accepting a connection, all data read from the client // is sent back to the client. The read and echo back to the client pattern // is continued until the client disconnects. class Server { private int m_numConnections; // the maximum number of connections the sample is designed to handle simultaneously private int m_receiveBufferSize;// buffer size to use for each socket I/O operation BufferManager m_bufferManager; // represents a large reusable set of buffers for all socket operations const int opsToPreAlloc = 2; // read, write (don't alloc buffer space for accepts) Socket listenSocket; // the socket used to listen for incoming connection requests // pool of reusable SocketAsyncEventArgs objects for write, read and accept socket operations SocketAsyncEventArgsPool m_readWritePool; int m_totalBytesRead; // counter of the total # bytes received by the server int m_numConnectedSockets; // the total number of clients connected to the server Semaphore m_maxNumberAcceptedClients; // Create an uninitialized server instance. // To start the server listening for connection requests // call the Init method followed by Start method // // <param name="numConnections">the maximum number of connections the sample is designed to handle simultaneously</param> // <param name="receiveBufferSize">buffer size to use for each socket I/O operation</param> public Server(int numConnections, int receiveBufferSize) { m_totalBytesRead = 0; m_numConnectedSockets = 0; m_numConnections = numConnections; m_receiveBufferSize = receiveBufferSize; // allocate buffers such that the maximum number of sockets can have one outstanding read and //write posted to the socket simultaneously m_bufferManager = new BufferManager(receiveBufferSize * numConnections * opsToPreAlloc, receiveBufferSize); m_readWritePool = new SocketAsyncEventArgsPool(numConnections); m_maxNumberAcceptedClients = new Semaphore(numConnections, numConnections); } // Initializes the server by preallocating reusable buffers and // context objects. These objects do not need to be preallocated // or reused, but it is done this way to illustrate how the API can // easily be used to create reusable objects to increase server performance. // public void Init() { // Allocates one large byte buffer which all I/O operations use a piece of. This gaurds // against memory fragmentation m_bufferManager.InitBuffer(); // preallocate pool of SocketAsyncEventArgs objects SocketAsyncEventArgs readWriteEventArg; for (int i = 0; i < m_numConnections; i ++ ) { //Pre-allocate a set of reusable SocketAsyncEventArgs readWriteEventArg = new SocketAsyncEventArgs(); readWriteEventArg.Completed + = new EventHandler<SocketAsyncEventArgs>(IO_Completed); // assign a byte buffer from the buffer pool to the SocketAsyncEventArg object m_bufferManager.SetBuffer(readWriteEventArg); // add SocketAsyncEventArg to the pool m_readWritePool.Push(readWriteEventArg); } } // Starts the server such that it is listening for // incoming connection requests. // // <param name="localEndPoint">The endpoint which the server will listen // for connection requests on</param> public void Start(IPEndPoint localEndPoint) { // create the socket which listens for incoming connections listenSocket = new Socket(localEndPoint. AddressFamily, SocketType. Stream, ProtocolType. Tcp); listenSocket. Bind(localEndPoint); // start the server with a listen backlog of 100 connections listenSocket. Listen(100); // post accepts on the listening socket SocketAsyncEventArgs acceptEventArg = new SocketAsyncEventArgs(); acceptEventArg.Completed + = new EventHandler<SocketAsyncEventArgs>(AcceptEventArg_Completed); StartAccept(acceptEventArg); //Console.WriteLine("{0} connected sockets with one outstanding receive posted to each....press any key", m_outstandingReadCount); Console.WriteLine("Press any key to terminate the server process...."); Console. ReadKey(); } // Begins an operation to accept a connection request from the client // // <param name="acceptEventArg">The context object to use when issuing // the accept operation on the server's listening socket</param> public void StartAccept(SocketAsyncEventArgs acceptEventArg) { // loop while the method completes synchronously bool willRaiseEvent = false; while (!willRaiseEvent) { m_maxNumberAcceptedClients.WaitOne(); // socket must be cleared since the context object is being reused acceptEventArg.AcceptSocket = null; willRaiseEvent = listenSocket. AcceptAsync(acceptEventArg); if (!willRaiseEvent) { ProcessAccept(acceptEventArg); } } } // This method is the callback method associated with Socket.AcceptAsync // operations and is invoked when an accept operation is complete // void AcceptEventArg_Completed(object sender, SocketAsyncEventArgs e) { ProcessAccept(e); // Accept the next connection request StartAccept(e); } private void ProcessAccept(SocketAsyncEventArgs e) { Interlocked.Increment(ref m_numConnectedSockets); Console.WriteLine("Client connection accepted. There are {0} clients connected to the server", m_numConnectedSockets); // Get the socket for the accepted client connection and put it into the //ReadEventArg object user token SocketAsyncEventArgs readEventArgs = m_readWritePool. Pop(); readEventArgs.UserToken = e.AcceptSocket; // As soon as the client is connected, post a receive to the connection bool willRaiseEvent = e.AcceptSocket.ReceiveAsync(readEventArgs); if (!willRaiseEvent) { ProcessReceive(readEventArgs); } } // This method is called whenever a receive or send operation is completed on a socket // // <param name="e">SocketAsyncEventArg associated with the completed receive operation</param> void IO_Completed(object sender, SocketAsyncEventArgs e) { // determine which type of operation just completed and call the associated handler switch (e. LastOperation) { case SocketAsyncOperation. Receive: ProcessReceive(e); break; case SocketAsyncOperation. Send: ProcessSend(e); break; default: throw new ArgumentException("The last operation completed on the socket was not a receive or send"); } } // This method is invoked when an asynchronous receive operation completes. // If the remote host closed the connection, then the socket is closed. // If data was received then the data is echoed back to the client. // private void ProcessReceive(SocketAsyncEventArgs e) { // check if the remote host closed the connection if (e.BytesTransferred > 0 & & e.SocketError == SocketError.Success) { //increment the count of the total bytes received by the server Interlocked.Add(ref m_totalBytesRead, e.BytesTransferred); Console.WriteLine("The server has read a total of {0} bytes", m_totalBytesRead); //echo the data received back to the client e.SetBuffer(e.Offset, e.BytesTransferred); Socket socket = (Socket)e. UserToken; bool willRaiseEvent = socket.SendAsync(e); if (!willRaiseEvent) { ProcessSend(e); } } else { CloseClientSocket(e); } } // This method is invoked when an asynchronous send operation completes. // The method issues another receive on the socket to read any additional // data sent from the client // // <param name="e"></param> private void ProcessSend(SocketAsyncEventArgs e) { if (e. SocketError == SocketError. Success) { // done echoing data back to the client Socket socket = (Socket)e. UserToken; // read the next block of data send from the client bool willRaiseEvent = socket. ReceiveAsync(e); if (!willRaiseEvent) { ProcessReceive(e); } } else { CloseClientSocket(e); } } private void CloseClientSocket(SocketAsyncEventArgs e) { Socket socket = (Socket)e. UserToken; // close the socket associated with the client try { socket.Shutdown(SocketShutdown.Send); } // throws if client process has already closed catch (Exception) { } socket. Close(); // decrement the counter keeping track of the total number of clients connected to the server Interlocked. Decrement(ref m_numConnectedSockets); // Free the SocketAsyncEventArg so they can be reused by another client m_readWritePool. Push(e); m_maxNumberAcceptedClients.Release(); Console.WriteLine("A client has been disconnected from the server. There are {0} clients connected to the server", m_numConnectedSockets); } }