c# - Socket Programming multiple client one server

Question

I am just starting out Socket Programming in C# and am now a bit stuck with this problem. How do you handle multiple clients on a single server without creating a thread for each client?

The one thread for each client works fine when there are say 10 clients but if the client number goes up to a 1000 clients is creating a thread for every single one of them advisable? If there is any other method to do this can someone please tel me?

Answer 1

Try to use asynchronous server. The following example program creates a server that receives connection requests from clients. The server is built with an asynchronous socket, so execution of the server application is not suspended while it waits for a connection from a client. The application receives a string from the client, displays the string on the console, and then echoes the string back to the client. The string from the client must contain the string "" to signal the end of the message.

    using System;
    using System.Net;
    using System.Net.Sockets;
    using System.Text;
    using System.Threading;

    // State object for reading client data asynchronously
    public class StateObject {
        // Client  socket.
        public Socket workSocket = null;
        // Size of receive buffer.
        public const int BufferSize = 1024;
        // Receive buffer.
        public byte[] buffer = new byte[BufferSize];
    // Received data string.
        public StringBuilder sb = new StringBuilder();  
    }

    public class AsynchronousSocketListener {
        // Thread signal.
        public static ManualResetEvent allDone = new ManualResetEvent(false);

        public AsynchronousSocketListener() {
        }

        public static void StartListening() {
            // Data buffer for incoming data.
            byte[] bytes = new Byte[1024];

            // Establish the local endpoint for the socket.
            // The DNS name of the computer
            // running the listener is "host.contoso.com".
            IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
            IPAddress ipAddress = ipHostInfo.AddressList[0];
            IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);

            // Create a TCP/IP socket.
            Socket listener = new Socket(AddressFamily.InterNetwork,
                SocketType.Stream, ProtocolType.Tcp );

            // Bind the socket to the local endpoint and listen for incoming connections.
            try {
                listener.Bind(localEndPoint);
                listener.Listen(100);

                while (true) {
                    // Set the event to nonsignaled state.
                    allDone.Reset();

                    // Start an asynchronous socket to listen for connections.
                    Console.WriteLine("Waiting for a connection...");
                    listener.BeginAccept( 
                        new AsyncCallback(AcceptCallback),
                        listener );

                    // Wait until a connection is made before continuing.
                    allDone.WaitOne();
                }

            } catch (Exception e) {
                Console.WriteLine(e.ToString());
            }

            Console.WriteLine("
Press ENTER to continue...");
            Console.Read();

        }

        public static void AcceptCallback(IAsyncResult ar) {
            // Signal the main thread to continue.
            allDone.Set();

            // Get the socket that handles the client request.
            Socket listener = (Socket) ar.AsyncState;
            Socket handler = listener.EndAccept(ar);

            // Create the state object.
            StateObject state = new StateObject();
            state.workSocket = handler;
            handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReadCallback), state);
        }

        public static void ReadCallback(IAsyncResult ar) {
            String content = String.Empty;

            // Retrieve the state object and the handler socket
            // from the asynchronous state object.
            StateObject state = (StateObject) ar.AsyncState;
            Socket handler = state.workSocket;

            // Read data from the client socket. 
            int bytesRead = handler.EndReceive(ar);

            if (bytesRead > 0) {
                // There  might be more data, so store the data received so far.
                state.sb.Append(Encoding.ASCII.GetString(
                    state.buffer,0,bytesRead));

                // Check for end-of-file tag. If it is not there, read 
                // more data.
                content = state.sb.ToString();
                if (content.IndexOf("<EOF>") > -1) {
                    // All the data has been read from the 
                    // client. Display it on the console.
                    Console.WriteLine("Read {0} bytes from socket. 
 Data : {1}",
                        content.Length, content );
                    // Echo the data back to the client.
                    Send(handler, content);
                } else {
                    // Not all data received. Get more.
                    handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                    new AsyncCallback(ReadCallback), state);
                }
            }
        }

        private static void Send(Socket handler, String data) {
            // Convert the string data to byte data using ASCII encoding.


      byte[] byteData = Encoding.ASCII.GetBytes(data);

        // Begin sending the data to the remote device.
        handler.BeginSend(byteData, 0, byteData.Length, 0,
            new AsyncCallback(SendCallback), handler);
    }

    private static void SendCallback(IAsyncResult ar) {
        try {
            // Retrieve the socket from the state object.
            Socket handler = (Socket) ar.AsyncState;

            // Complete sending the data to the remote device.
            int bytesSent = handler.EndSend(ar);
            Console.WriteLine("Sent {0} bytes to client.", bytesSent);

            handler.Shutdown(SocketShutdown.Both);
            handler.Close();

        } catch (Exception e) {
            Console.WriteLine(e.ToString());
        }
    }   

    public static int Main(String[] args) {
        StartListening();
        return 0;
    }
}

That's will be the best solution.