使用.NET访问Internet(4) Paul_Ni（原作）(补充)

2024-07-10 13:08:12

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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/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;
  }<