socket

ServerSocket ss = new ServerSocket(port);
  while(true){ //如果有客户端的连接请求，将执行下面的操作
  Socket client = ss.accept(); //新建客户端对象
  Handle handle = new Handle(client);//启动个客户端线程,并且一直监听，直到退出，若有多个客户端请求,则会新建多个客户端线程，由此实现多线程
  }


public class Handle implements Runnable{
Socket socket;
public Handle(Socket socket){
this.socket = socket;
new Thread(this).start();  
}
public void run(){
try{
  BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
            writer.write("返回服务器处理的消息给客户端");
            writer.flush();
            writer.close();//关闭这个socket

         } catch (Exception e){
}
}