Asynchronous Client Socket Example

 

The following example program creates a client that connects to a server. The client is built with an asynchronous socket, so execution of the client application is not suspended while the server returns a response. The application sends a string to the server and then displays the string returned by the server on the console.

using System;  
using System.Net;  
using System.Net.Sockets;  
using System.Threading;  
using System.Text;  
  
// State object for receiving data from remote device.  
public class StateObject {  
    // Client socket.  
    public Socket workSocket = null;  
    // Size of receive buffer.  
    public const int BufferSize = 256;  
    // Receive buffer.  
    public byte[] buffer = new byte[BufferSize];  
    // Received data string.  
    public StringBuilder sb = new StringBuilder();  
}  
  
public class AsynchronousClient {  
    // The port number for the remote device.  
    private const int port = 11000;  
  
    // ManualResetEvent instances signal completion.  
    private static ManualResetEvent connectDone =   
        new ManualResetEvent(false);  
    private static ManualResetEvent sendDone =   
        new ManualResetEvent(false);  
    private static ManualResetEvent receiveDone =   
        new ManualResetEvent(false);  
  
    // The response from the remote device.  
    private static String response = String.Empty;  
  
    private static void StartClient() {  
        // Connect to a remote device.  
        try {  
            // Establish the remote endpoint for the socket.  
            // The name of the   
            // remote device is "host.contoso.com".  
            IPHostEntry ipHostInfo = Dns.Resolve("host.contoso.com");  
            IPAddress ipAddress = ipHostInfo.AddressList[0];  
            IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);  
  
            // Create a TCP/IP socket.  
            Socket client = new Socket(AddressFamily.InterNetwork,  
                SocketType.Stream, ProtocolType.Tcp);  
  
            // Connect to the remote endpoint.  
            client.BeginConnect( remoteEP,   
                new AsyncCallback(ConnectCallback), client);  
            connectDone.WaitOne();  
  
            // Send test data to the remote device.  
            Send(client,"This is a test<EOF>");  
            sendDone.WaitOne();  
  
            // Receive the response from the remote device.  
            Receive(client);  
            receiveDone.WaitOne();  
  
            // Write the response to the console.  
            Console.WriteLine("Response received : {0}", response);  
  
            // Release the socket.  
            client.Shutdown(SocketShutdown.Both);  
            client.Close();  
  
        } catch (Exception e) {  
            Console.WriteLine(e.ToString());  
        }  
    }  
  
    private static void ConnectCallback(IAsyncResult ar) {  
        try {  
            // Retrieve the socket from the state object.  
            Socket client = (Socket) ar.AsyncState;  
  
            // Complete the connection.  
            client.EndConnect(ar);  
  
            Console.WriteLine("Socket connected to {0}",  
                client.RemoteEndPoint.ToString());  
  
            // Signal that the connection has been made.  
            connectDone.Set();  
        } catch (Exception e) {  
            Console.WriteLine(e.ToString());  
        }  
    }  
  
    private static void Receive(Socket client) {  
        try {  
            // Create the state object.  
            StateObject state = new StateObject();  
            state.workSocket = client;  
  
            // Begin receiving the data from the remote device.  
            client.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,  
                new AsyncCallback(ReceiveCallback), state);  
        } catch (Exception e) {  
            Console.WriteLine(e.ToString());  
        }  
    }  
  
    private static void ReceiveCallback( IAsyncResult ar ) {  
        try {  
            // Retrieve the state object and the client socket   
            // from the asynchronous state object.  
            StateObject state = (StateObject) ar.AsyncState;  
            Socket client = state.workSocket;  
  
            // Read data from the remote device.  
            int bytesRead = client.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));  
  
                // Get the rest of the data.  
                client.BeginReceive(state.buffer,0,StateObject.BufferSize,0,  
                    new AsyncCallback(ReceiveCallback), state);  
            } else {  
                // All the data has arrived; put it in response.  
                if (state.sb.Length > 1) {  
                    response = state.sb.ToString();  
                }  
                // Signal that all bytes have been received.  
                receiveDone.Set();  
            }  
        } catch (Exception e) {  
            Console.WriteLine(e.ToString());  
        }  
    }  
  
    private static void Send(Socket client, 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.  
        client.BeginSend(byteData, 0, byteData.Length, 0,  
            new AsyncCallback(SendCallback), client);  
    }  
  
    private static void SendCallback(IAsyncResult ar) {  
        try {  
            // Retrieve the socket from the state object.  
            Socket client = (Socket) ar.AsyncState;  
  
            // Complete sending the data to the remote device.  
            int bytesSent = client.EndSend(ar);  
            Console.WriteLine("Sent {0} bytes to server.", bytesSent);  
  
            // Signal that all bytes have been sent.  
            sendDone.Set();  
        } catch (Exception e) {  
            Console.WriteLine(e.ToString());  
        }  
    }  
  
    public static int Main(String[] args) {  
        StartClient();  
        return 0;  
    }  
}  

Asynchronous Server Socket Example
Using a Synchronous Server Socket
Socket Code Examples

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