代码：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
 
/**
 * 发送消息线程
 */
class Send extends Thread{
    private Socket socket;
    public Send(Socket socket){
        this.socket  =socket;
    }
    @Override
    public void run() {
        this.sendMsy();
    }
    /**
     * 发送消息
     */
    private void sendMsy(){
        Scanner scanner =null;
        PrintWriter pw =null;
        try{
            scanner =new Scanner(System.in);
            pw =new PrintWriter(this.socket.getOutputStream());
            while(true){
                String str =scanner.nextLine();
                pw.println(str);
                pw.flush();
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (scanner!=null){
                scanner.close();
            }
            if (pw!=null){
                pw.close();
            }
            if (socket!=null){
                try {
                    socket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}
 
/**
 * 接收消息的线程
 */
class receive extends Thread{
    private Socket socket=null;
    public receive(Socket socket){
        this.socket =socket;
    }
 
    @Override
    public void run() {
        this.receiveMsg();
    }
    /**
     * 用于接收对方消息
     */
    private void receiveMsg(){
        BufferedReader br =null;
        try{
            br =new BufferedReader(new InputStreamReader(this.socket.getInputStream()));
            while(true){
                String mr = br.readLine();
                System.out.println("B说："+mr);
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (br!=null){
                try {
                    br.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
 
        }
    }
}
 
public class ChatSocketServer {
    public static void main(String[] args) {
        ServerSocket serverSocket =null;
        try{
            serverSocket =new ServerSocket(8888);
            System.out.println("服务端已启动等待连接");
            Socket socket = serverSocket.accept();
            System.out.println("连接成功！");
            new Send(socket).start();
            new receive(socket).start();
        }catch(Exception e){
            e.printStackTrace();
        }finally {
            if (serverSocket!=null){
                try {
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

结果：