java 网络编程

一、TCP实现小型聊天室

实现方法：服务器端接受所有的消息，然后把接收到的每一条消息发送给所有已连接的设备上去。

服务器端代码：

package com.TCP;

import java.util.*;


import java.net.*;
import java.io.*;
public class TCPServer_2 {
    
    private int no = 0; //为连接设备编号

    // 保存当前连接的客户端Socket
    private List<Socket> sockList = Collections.synchronizedList(new ArrayList<Socket>());

    class ServerThread implements Runnable {
        int no;
        Socket s;
        BufferedReader br;

        public ServerThread(Socket s, int no) {
            this.s = s;
            this.no = no;
            try {
                br = new BufferedReader(new InputStreamReader(s.getInputStream()));
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        private String getContentByLine() {
            try {
                return br.readLine();
            } catch (IOException e) { // 该请求可能已被客户端关闭
                e.printStackTrace();
                sockList.remove(s); // 因此需要从列表中移除
            }
            return null;
        }

        @Override
        public void run() {
            String content = "";
            while ((content = getContentByLine()) != null) {
            // 只要客户端不关闭Socket，那么输入输出流就是一直开着的
            // 服务器端会一直等待输入，永远也到不了EOF使getContentByLine返回null
                for (Socket s: sockList) { // 对每一个连接的客户端都发送聊天信息
                    PrintStream ps;
                    try {
//                        ps = new PrintStream(s.getOutputStream());
//                        ps.println("#" + no + " says: " + content);
//                        ps.println(x);
                        DataOutputStream dataOut = new DataOutputStream(s.getOutputStream());
                        if("CI".equals(content.substring(0, 2))){
                            dataOut.writeBytes("SCXX" + '
');
                        }
                        else if("CS".equals(content.substring(0, 2))){
                            dataOut.writeBytes("SLXX" + '
');
                        }else{
                            dataOut.writeBytes("#" + no + " says: " + content);
                        }
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        }

    }
    
    public void init() throws IOException {
//        ServerSocket ss = new ServerSocket(8000, 10, InetAddress.getByName("192.168.96.1")); // 使用默认IP，端口3000
        ServerSocket ss = new ServerSocket(8000);
        while (true) {
            Socket s = ss.accept();
            no += 1;
            System.out.println("#" + no + " connected!");
            sockList.add(s);
            new Thread(new ServerThread(s, no)).start();
        }
    }

    public static void main(String[] args) throws IOException {
        new TCPServer_2().init();
    }

}

客户端代码：

package com.TCP;

import java.util.*;
import java.net.*;
import java.io.*;
public class TCPClient_2 {
    

    class ClientThread implements Runnable {
        private Socket s;

        public ClientThread(Socket s) {
            this.s = s;
        }

        @Override
        public void run() {
            try {
                String content = "";
                BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
                while ((content = br.readLine()) != null) { // 不断读取服务器发来的广播消息
                    System.out.println(content);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    public void init() throws UnknownHostException, IOException {
        Socket s = new Socket("192.168.1.106", 8000);
        new Thread(new ClientThread(s)).start(); // 建立连接后马上监控广播消息

        PrintStream ps = new PrintStream(s.getOutputStream()); // 输出流定向到远程
        
        String line = "";
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        while ((line = br.readLine()) != null) { // 从控制台键盘读取输入
            ps.println(line); // 发送到远程
        }
    }

    public static void main(String[] args) throws UnknownHostException, IOException {
        new TCPClient_2().init();
    }

}

二、UDP实现组播播消息（UDP没有c/s概念，所以多开几个程序就能相互通信了）

package com.UDP_Port;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import java.util.Scanner;

public class UDPMulticast {

    private final static String BC_IP = "230.0.0.1"; // 组播地址
    private final static int BC_PORT = 30000; // 组播端口
    private final static int PACK_SIZE = 4096;

    public void init() throws IOException {
        MulticastSocket sock = new MulticastSocket(BC_PORT);
        InetAddress bcAddr = InetAddress.getByName(BC_IP);
        try (Scanner scan = new Scanner(System.in)) {
            // 创建socket并加入组播地址
            sock.joinGroup(bcAddr);
            sock.setLoopbackMode(false); // 必须是false才能开启广播功能！！

            new Thread(() -> { // 接受广播消息的线程
                try {
                    DatagramPacket inpack = new DatagramPacket(new byte[PACK_SIZE], PACK_SIZE);
                    while (true) {
                        sock.receive(inpack);
                        System.out.println("广播消息：" + new String(inpack.getData(), 0, inpack.getLength()));
                    }
                } catch (IOException e) {
                    e.printStackTrace();
                    if (sock != null) {
                        try {
                            sock.leaveGroup(bcAddr);
                        } catch (Exception e1) {
                            // TODO Auto-generated catch block
                            e1.printStackTrace();
                        }
                        sock.close();
                    }
                    System.exit(1);
                }
            }).start();

            // 主线程接受控制台输入并广播出去
            DatagramPacket outpack = new DatagramPacket(new byte[0], 0, bcAddr, BC_PORT); // 目的端口和MulticastSocket端口一样！！
            while (scan.hasNextLine()) {
                byte[] buf = scan.nextLine().getBytes();
                outpack.setData(buf);
                sock.send(outpack);
            }
        } finally { // 最终关闭程序之前一定要关闭socket
            sock.close();
        }
    }

    public static void main(String[] args) throws NumberFormatException, IOException {
        // TODO Auto-generated method stub
        new UDPMulticast().init();
    }

}