实现多客户端与服务端的连接，并实现群聊效果

1.创建客户端口

package com.test4;

import java.io.IOException;
import java.net.Socket;
import java.util.ArrayList;


public class KHD {
    public static void main(String[] args) throws IOException {
        Socket link = new Socket("127.0.0.1", 6666);


        XcReader reader = new XcReader(link);
        Thread t = new Thread(reader);
        t.start();

        XcWriter writer = new XcWriter(link);
        writer.start();



    }
}

2.创建服务端口

package com.test4;


import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;

public class FWD {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(6666);

        System.out.println("启动");
        //装载所有与服务端连接的客户端信息
        List<Socket> allLink = new ArrayList<>();
        for (int i = 0; i < 50; i++) {  //循环50个客户端
            Socket link = serverSocket.accept();
            allLink.add(link);

            //需要一个能读且能写的
            Thread t  = new RorW(link,allLink);
            t.start();

        }


    }
}

3.创建用于读取（接收消息）的线程

package com.test4;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.net.Socket;

public class XcReader implements Runnable {
    private Socket link;

    public XcReader(Socket link) {
        this.link = link;
    }

    @Override
    public void run() {
        try {
            InputStream is = link.getInputStream();
            Reader r = new InputStreamReader(is);

            while (true){
                StringBuilder str = new StringBuilder();
                while (true){
                    int a = r.read();
                    str.append((char)a);
                    if (str.toString().endsWith("[over]")){
                        break;
                    }
                }
                int i = str.indexOf("[over]");
                System.out.println("接受一条信息: "+str.substring(0,i));
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

4.创建用于说出（发送）的线程

package com.test4;

import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
import java.util.Scanner;

public class XcWriter extends Thread{
    private Socket link;

    public XcWriter(Socket link) {
        this.link = link;
    }

    @Override
    public void run() {
        try {
            OutputStream os = link.getOutputStream();

            while (true){
                Scanner input = new Scanner(System.in);
                System.out.println("发送一条消息:");
                os.write(input.nextLine().getBytes());
                os.write("[over]".getBytes());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

5.创建能读能写的线程

package com.test4;

import java.io.*;
import java.net.Socket;
import java.util.List;

public class RorW extends Thread {

    private Socket link;
    private List<Socket> allLink;

    public RorW(Socket link, List<Socket> allLink) {
        this.link = link;
        this.allLink = allLink;
    }

    @Override
    public void run() {

        try {
            InputStream is = link.getInputStream();
            Reader reader = new InputStreamReader(is);

            while (true) {

                StringBuilder str = new StringBuilder();
                //一遍一遍读
                char[] chars = new char[0x10];
                while (true) {
                    int len = reader.read(chars);
                    str.append(chars, 0, len);
                    if (str.toString().endsWith("[over]")) {
                        break;
                    }
                }
                //代码至此 收到发送信息
                String r = str.toString().replace("[over]", "");
                System.out.println("收到了来自【" + link.getInetAddress() + "】的客户信息" + r);

                //找到所有的客户端 写给他们信息
                for (Socket s : allLink) {
                    if (link == s) {  //找到了本身
                        continue;
                    }
                    //找到别的客户端
                    OutputStream os = s.getOutputStream();
                    os.write(r.getBytes());
                    os.write("[over]".getBytes());
                }
            }


        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

6.运行结果：

客户端发送消息通过服务端来为其他客户端发送消息 其他客户端完成接受消息已实现群聊效果