开始从客户端套接字接收数据的 acceptCallback 方法的此节首先初始化 StateObject 类的一个实例，然后调用 BeginReceive 方法以开始从客户端套接字异步读取数据。

下面的示例显示了完整的 acceptCallback 方法。它假定以下内容：存在一个名为 allDone 的 ManualResetEvent 实例，定义了 StateObject 类，以及在名为 SocketListener 的类中定义了 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);
}
需要为异步套接字服务器实现的 final 方法是返回客户端发送的数据的读取回调方法。与接受回调方法一样，读取回调方法也是一个 AsyncCallback 委托。该方法将来自客户端套接字的一个或多个字节读入数据缓冲区，然后再次调用 BeginReceive 方法，直到客户端发送的数据完成为止。从客户端读取整个消息后，在控制台上显示字符串，并关闭处理与客户端的连接的服务器套接字。

下面的示例实现 readCallback 方法。它假定定义了 StateObject 类。

[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();
}
}
同步客户端套接字示例
下面的示例程序创建一个连接到服务器的客户端。该客户端是用同步套接字生成的，因此挂起客户端应用程序的执行，直到服务器返回响应为止。该应用程序将字符串发送到服务器，然后在控制台显示该服务器返回的字符串。

[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/IPsocket.
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 thesocket.
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;
}