1.main方法：

package peixun;


public class MyServerSocket {

    public static void main(String[] args) {
        
        new ServerListener().start();
        
    }

}

2.建立连接

package peixun;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

import javax.swing.JOptionPane;

public class ServerListener extends Thread {

    @Override
    public void run() {

        try {
            //()内写的是监听的端口，可以是1-65535
            ServerSocket serverSocket = new ServerSocket(12345);
            while (true) {
                
                //侦听客户端的连接,会阻塞当前的线程
                Socket socket = serverSocket.accept();//此时已经监听12345这个端口了
                //建立连接
                JOptionPane.showMessageDialog(null, "有客户端链接到了本机的12345端口");
                
                //因为要与多个客户端交互，所以要将socket传递给新的线程，接下来就是创建与socket通信的线程
                new ChatSocket(socket).start();
                
                
            }
            
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

3.进行socket通信

package peixun;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.Socket;

public class ChatSocket extends Thread {

    Socket socket;
    
    public ChatSocket(Socket s) {
        this.socket = s;
    }
    
    public void out(String out) {
        try {
            socket.getOutputStream().write(out.getBytes("UTF-8"));
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    
    @Override
    public void run() {
        
        int count = 0;
        while (true) {
            count++;
            out("loop"+count);
            try {
                sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        
    }
    
}