1、即时通信是什么含义，要实现怎么样的设计？

• 即时通信，是指一个客户端的消息发出去，其他客户端可以接收到
• 即时通信需要进行端口转发的设计思想
• 服务端需要把在线的Socket管道存储起来
• 一旦收到一个消息要推送给其他管道

服务端 

package com.csdn.demo07_tcp5_sms;import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;/*** 目标：实现 服务端 可以同时处理 多个客户端 的消息*/
public class ServerDemo2 {//定义一个静态的List集合存储当前全部在线的socket管道public static List<Socket> allOnlineSockets = new ArrayList<>();public static void main(String[] args) {try {System.out.println("===服务端启动成功===");//1、注册端口ServerSocket serverSocket = new ServerSocket(7777);//a.定义一个死循环由主线程负责不断的接收客户端的Socket管道连接while (true) {//2、每接收到一个客户端的Socket管道，交给一个独立的子线程负责读取消息Socket socket = serverSocket.accept();//上线逻辑System.out.println(socket.getRemoteSocketAddress() + "上线了，来了老弟！！");allOnlineSockets.add(socket);//上线完成//3、开始创建独立线程处理socketnew ServerReaderThread(socket).start();}} catch (IOException e) {throw new RuntimeException(e);}}
}class ServerReaderThread extends Thread {private Socket socket;public ServerReaderThread(Socket socket) {this.socket = socket;}@Overridepublic void run() {try {//3、从socket通信管道中得到一个字节输入流InputStream is = socket.getInputStream();//4、把字节输入流包装成缓冲字符输入流进行消息的接收BufferedReader br = new BufferedReader(new InputStreamReader(is));//5、按照行读取消息String msg;while ((msg = br.readLine()) != null) {System.out.println(socket.getRemoteSocketAddress() + "发来了：" + msg);//把这个消息进行端口转发给全部客户端socket管道sendMsgToAll(msg);}} catch (IOException e) {System.out.println(socket.getRemoteSocketAddress() + "下线了，下次再来哦，老弟！！");ServerDemo2.allOnlineSockets.remove(socket);}}private void sendMsgToAll(String msg) throws IOException {for (Socket socket : ServerDemo2.allOnlineSockets) {PrintStream ps = new PrintStream(socket.getOutputStream());ps.println(msg);ps.flush();}}
}

 客户端

package com.csdn.demo07_tcp5_sms;import java.io.*;
import java.net.Socket;
import java.util.Scanner;/*** 目标：完成 Socket  客户端开发，实现 多发 和 多收*/
public class ClientDemo1 {public static void main(String[] args) {try{System.out.println("===客户端启动===");//1、创建Socket通信管道请求有服务端的连接Socket socket = new Socket("127.0.0.1", 7777);//创建一个独立的线程专门负责这个客户端的读消息（服务端随时可能转发消息过来！）new ClientReaderThread(socket).start();//2、从socket通信管道中得到一个字节输出流 负责发送数据OutputStream os = socket.getOutputStream();//3、把低级的字节流包装成打印流PrintStream ps = new PrintStream(os);Scanner sc = new Scanner(System.in);while (true) {System.out.println("请说：");String msg = sc.nextLine();//4、发送消息ps.println(msg);ps.flush();}} catch (IOException e) {throw new RuntimeException(e);}}
}class ClientReaderThread extends Thread {private Socket socket;public ClientReaderThread(Socket socket) {this.socket = socket;}@Overridepublic void run() {try {//3、字节输入流InputStream is = socket.getInputStream();//4、把低级的字节输入流包装成高级的缓冲字符输入流BufferedReader br = new BufferedReader(new InputStreamReader(is));//5、按照行读取String line;while ((line = br.readLine()) != null) {System.out.println("收到消息" + line);}} catch (IOException e) {System.out.println("服务器把你踢出去了~~~");}}
}