TCP通信——端口转发（重点内容）

实现多人群聊

Client(客户端）建立通信

package com.zz.tcp.case1;import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
import java.util.Scanner;public class Client {public static void main(String args[]) throws Exception {//1.创建Socket对象，并同时请求与服务端程序连接Socket socket = new Socket("127.0.0.1", 8888);//创建一个独立的线程，负责随机从socket中接收服务端的发送过来的消息new ClientReaderThread(socket).start();//2.从socket通信管道中的到一个字节输出流，用来发送数据OutputStream os = socket.getOutputStream();//将低级的字节输出流包装成数据输出流DataOutputStream dos = new DataOutputStream(os);Scanner sc = new Scanner(System.in);while(true){System.out.println("请说：");String msg = sc.nextLine();//一旦用户输入了exit就退出客户端程序if("exit".equals(msg)){System.out.println("欢迎您下次光临！");dos.close();socket.close();break;}//4.开始写数据出去dos.writeUTF(msg);//5.刷新数据，防止数据留在管道dos.flush();}}
}

ClientReaderThread（服务端线程类）——实现接收服务端转发的消息

package com.zz.tcp.case1;import java.io.*;
import java.net.Socket;public class ClientReaderThread extends Thread{private Socket socket;public ClientReaderThread(Socket socket) {this.socket = socket;}@Overridepublic void run() {try {InputStream is = socket.getInputStream();DataInputStream dis = new DataInputStream(is);while (true) {try {String msg = dis.readUTF();System.out.println(msg);//把这个消息发送给全部客户端进行接收sendMsgToAll(msg);} catch (Exception e) {System.out.println("自己下线了" + socket.getRemoteSocketAddress());dis.close();socket.close();break;}}} catch (IOException e) {e.printStackTrace();}}private void sendMsgToAll(String msg) throws IOException {//发送给全部在线的socket的管道接收for (Socket onLineSocket: Server.onLineSockets) {OutputStream os = onLineSocket.getOutputStream();DataOutputStream dos = new DataOutputStream(os);dos.writeUTF(msg);dos.flush();}}
}

Server（服务端）负责接收客户端的消息，通过8888端口建立连接

package com.zz.tcp.case1;import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;public class Server {public static List<Socket> onLineSockets = new ArrayList <>();public static void main(String args[]) throws Exception{System.out.println("========服务端启动========");//1.创建ServerSocket的对象，调用一个accept方法，等待客户端的连接请求ServerSocket serverSocket = new ServerSocket(8888);while (true){//2.使用ServerSocket对象，调用一个accept方法，等待客户端的连接请求Socket socket = serverSocket.accept();onLineSockets.add(socket);System.out.println("有人上线了" + socket.getRemoteSocketAddress());//3.把这个客户端对应的socket通信管道，交给一个独立的线程复制处理new ServerReaderThread(socket).start();}}
}

ServerReaderThread（客户端线程类）——负责接受客户端发的消息，然后转发给其他客户端

package com.zz.tcp.case1;import java.io.*;
import java.net.Socket;public class ServerReaderThread extends Thread{private Socket socket;public ServerReaderThread(Socket socket) {this.socket = socket;}@Overridepublic void run() {try {InputStream is = socket.getInputStream();DataInputStream dis = new DataInputStream(is);while (true) {try {String msg = dis.readUTF();System.out.println(msg);//把这个消息发送给全部客户端进行接收sendMsgToAll(msg);} catch (Exception e) {System.out.println("有人下线了" + socket.getRemoteSocketAddress());Server.onLineSockets.remove(socket);dis.close();socket.close();break;}}} catch (IOException e) {e.printStackTrace();}}private void sendMsgToAll(String msg) throws IOException {//发送给全部在线的socket的管道接收for (Socket onLineSocket: Server.onLineSockets) {OutputStream os = onLineSocket.getOutputStream();DataOutputStream dos = new DataOutputStream(os);dos.writeUTF(msg);dos.flush();}}
}