How To Series: C# 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.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 | using System; using System.Net; using System.Net.Sockets; using System.Threading; using System.Text; </code> // 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.GetHostEntry("host.contoso.com"); IPAddress ipAddress = ipHostInfo.AddressList[0]; IPEndPoint remoteEP = new IPEndPoint(ipAddress, port); // Create a TCP/IP socket. Socket client = new Socket(ipAddress.AddressFamily, 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"); 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; } } |