使用.NET訪問Internet(4) Paul

開始從用戶端通訊端接收資料的 acceptCallback 方法的此節首先初始化 StateObject 類的一個執行個體，然後調用 BeginReceive 方法以開始從用戶端通訊端非同步讀取資料。 下面的樣本顯示了完整的 acceptCallback 方法。它假定以下內容：存在一個名為 allDone 的 ManualResetEvent 執行個體，定義了 StateObject 類，以及在名為 SocketListener 的類中定義了 readCallback 方法。 [C#]   public static void acceptCallback(IAsyncResult ar) {     // Get the socket that handles the client request.     Socket listener = (Socket) ar.AsyncState;     Socket handler = listener.EndAccept(ar);     // Signal the main thread to continue.     allDone.Set();     // Create the state object.     StateObject state = new StateObject();     state.workSocket = handler;     handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,       new AsyncCallback(AsynchronousSocketListener.readCallback), state);   } 需要為非同步通訊端伺服器實現的 final 方法是返回用戶端發送的資料的讀取回調方法。與接受回調方法一樣，讀取回調方法也是一個 AsyncCallback 委託。該方法將來自用戶端通訊端的一個或多個位元組讀入資料緩衝區，然後再次調用 BeginReceive 方法，直到用戶端發送的資料完成為止。從用戶端讀取整個訊息後，在控制台上顯示字串，並關閉處理與用戶端的已連線的服務器通訊端。 下面的樣本實現 readCallback 方法。它假定定義了 StateObject 類。 [C#] public void readCallback(IAsyncResult ar) {   StateObject state = (StateObject) ar.AsyncState;   Socket handler = state.WorkSocket;   // Read data from the client socket.   int read = handler.EndReceive(ar);   // Data was read from the client socket.   if (read > 0) {     state.sb.Append(Encoding.ASCII.GetString(state.buffer,0,read));     handler.BeginReceive(state.buffer,0,StateObject.BufferSize, 0,       new AsyncCallback(readCallback), state);   } else {     if (state.sb.Length > 1) {       // All the data has been read from the client;       // display it on the console.       string content = state.sb.ToString();       Console.WriteLine("Read {0} bytes from socket.\n Data : {1}",         content.Length, content);     }     handler.Close();   } } 同步用戶端通訊端樣本 下面的樣本程式建立一個串連到伺服器的用戶端。該用戶端是用同步通訊端產生的，因此掛起用戶端應用程式的執行，直到伺服器返迴響應為止。該應用程式將字串發送到伺服器，然後在控制台顯示該伺服器返回的字串。 [C#] using System; using System.Net; using System.Net.Sockets; using System.Text; public class SynchronousSocketClient {   public static void StartClient() {     // Data buffer for incoming data.     byte[] bytes = new byte[1024];     // 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,11000);       // Create a TCP/IP  socket.       Socket sender = new Socket(AddressFamily.InterNetwork,         SocketType.Stream, ProtocolType.Tcp );       // Connect the socket to the remote endpoint. Catch any errors.       try {         sender.Connect(remoteEP);         Console.WriteLine("Socket connected to {0}",           sender.RemoteEndPoint.ToString());         // Encode the data string into a byte array.         byte[] msg = Encoding.ASCII.GetBytes("This is a test<EOF>");         // Send the data through the  socket.         int bytesSent = sender.Send(msg);         // Receive the response from the remote device.         int bytesRec = sender.Receive(bytes);         Console.WriteLine("Echoed test = {0}",           Encoding.ASCII.GetString(bytes,0,bytesRec));         // Release the socket.         sender.Shutdown(SocketShutdown.Both);         sender.Close();                } catch (ArgumentNullException ane) {         Console.WriteLine("ArgumentNullException : {0}",ane.ToString());       } catch (SocketException se) {         Console.WriteLine("SocketException : {0}",se.ToString());       } catch (Exception e) {         Console.WriteLine("Unexpected exception : {0}", e.ToString());       }     } catch (Exception e) {       Console.WriteLine( e.ToString());     }   }      public static int Main(String[] args) {     StartClient();     return 0;   }<