基于Java的 Socket 多客户端 Client-Server 聊天程序

任务要求

编写一个简单的Socket多客户端聊天程序：

• 客户端程序，从控制台输入字符串，发送到服务器端，并将服务器返回的信息显示出来
• 服务器端程序，从客户机接收数据并打印，同时将从标准输入获取的信息发送给客户机
• 满足一个服务器可以服务多个客户

低配版本链接

实现代码

工具类

import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;

public class SocketUtils {
	
	public static void writeToSocket(Socket socket, String message) throws IOException {
		writeToOutputStream(socket.getOutputStream(), message);
	}
	
	public static void writeToDataOutputStream(DataOutputStream dos, String message) throws IOException {
		dos.writeUTF(message);
		dos.flush();
	}
	
	public static void writeToOutputStream(OutputStream os, String message) throws IOException {
		writeToDataOutputStream(new DataOutputStream(os), message);
	}

}

服务器端线程

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Map;

public class ChatServerRunnable implements Runnable {

	private Socket socket;

	private DataOutputStream dos;

	private DataInputStream dis;

	private String currentUserNickName;

	public ChatServerRunnable(Socket socket) throws IOException {
		this.socket = socket;
		this.dos = new DataOutputStream(socket.getOutputStream());
		this.dis = new DataInputStream(socket.getInputStream());
	}

	@Override
	public void run() {
		try {
			write("欢迎来到聊天室！");
			login();
			System.out.println(currentUserNickName + "用户登录成功");
			write(currentUserNickName + "， 您已登录。\n输入【list users】可以查看当前登录用户列表\n输入【to all 消息内容】可以群发消息\n输入【to 某个用户 消息内容】可以给指定用户发送消息\n输入【exit】可以退出聊天");
			String input = dis.readUTF();
			while (!ChatServer.EXIT.equals(input)) {
				System.out.println(currentUserNickName + "输入了" + input);
				if (input.startsWith("to ")) {
					sendMessage(input);
				} else if ("list users".equals(input)) {
					showOnlineUsers();
				} else {
					write("您输入的命令不合法，请重新输入！");
				}
				input = dis.readUTF();
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			ChatServer.nickNameSocketMap.remove(currentUserNickName);
			try {
				dis.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			try {
				dos.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			try {
				socket.close();
			} catch (IOException e) {
				e.printStackTrace();
			}

		}
	}

	private void login() throws IOException {
		write("请输入你的昵称：");
		while (true) {
			String nickName = dis.readUTF();
			System.out.println("用户输入了昵称：" + nickName);
			synchronized (ChatServerRunnable.class) {
				if (!ChatServer.nickNameSocketMap.containsKey(nickName)) {
					currentUserNickName = nickName;
					ChatServer.nickNameSocketMap.put(nickName, socket);
					break;
				} else {
					write("您输入的昵称已存在，请重新输入：");
				}
			}
		}
	}

	private void sendMessage(String input) throws IOException {
		int receiverEndIndex = input.indexOf(" ", 3);
		String receiver = input.substring(3, receiverEndIndex);
		String message = input.substring(receiverEndIndex + 1);
		if ("all".equals(receiver)) {
			broadcast(message);
		} else {
			sendIndividualMessage(receiver, message);
		}
	}

	private void sendIndividualMessage(String receiver, String orignalMessage) throws IOException {
		Socket receiverSocket = ChatServer.nickNameSocketMap.get(receiver);
		if (receiverSocket != null) {
			SocketUtils.writeToSocket(receiverSocket, formatMessage("你", orignalMessage));
		} else {
			write("您要单独聊天的用户【" + receiver + "】不存在或者已经下线");
		}
	}

	private String formatMessage(String receiver, String originalMessage) {
		StringBuilder messageBuilder = new StringBuilder();
		messageBuilder.append(currentUserNickName).append(" 对 ").append(receiver).append(" 说：\n")
				.append(originalMessage).append("\n发送时间：")
				.append(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()));
		return messageBuilder.toString();
	}

	private void broadcast(String orignalMessage) throws IOException {
		for (Map.Entry<String, Socket> entry : ChatServer.nickNameSocketMap.entrySet()) {
			if (!currentUserNickName.equals(entry.getKey())) {
				SocketUtils.writeToSocket(entry.getValue(), formatMessage("所有人", orignalMessage));
			}
		}
	}
	
	private void showOnlineUsers() throws IOException {
		StringBuilder users = new StringBuilder();
		users.append("当前在线的用户有：\n");
		for (String nickName : ChatServer.nickNameSocketMap.keySet()) {
			users.append("【").append(nickName).append("】\n");
		}
		write(users.toString());
	}

	private void write(String message) throws IOException {
		SocketUtils.writeToDataOutputStream(dos, message);
	}

}

客户端线程

import java.io.DataInputStream;
import java.io.IOException;

public class ClientMessageReceiver implements Runnable {
	
	private DataInputStream dis;
	
	private boolean timeToStop = false;
	
	public ClientMessageReceiver(DataInputStream dis) {
		this.dis = dis;
	}

	@Override
	public void run() {
		while (!timeToStop) {
			try {
				System.out.println(dis.readUTF());
			} catch (IOException e) {
				if ("Connection reset".equals(e.getMessage())) {
					System.out.println("与服务器的连接已中断！");
					break;
				}
				if (!timeToStop) {
					e.printStackTrace();					
				}
			}
		}
	}
	
	public void stop() {
		timeToStop = true;
	}

}

服务器端程序

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashMap;
import java.util.Map;

public class ChatServer {
	
	public static final String EXIT = "exit";
	
	public static final int PORT = 8888;
	
	static Map<String, Socket> nickNameSocketMap = new HashMap<>();

	public static void main(String[] args) {
		try (ServerSocket ss = new ServerSocket(PORT)) {
			System.out.println("聊天室服务器端已启动，正在监听" + PORT + "端口");
			while (true) {
				try {
					Socket socket = ss.accept();
					System.out.println("有新用户连接到服务器端，信息为：" + socket);
					new Thread(new ChatServerRunnable(socket)).start();
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		} catch (IOException e) {
			e.printStackTrace();
		}

	}

}

客户端程序

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.util.Scanner;

public class ChatClient {
	
	private static Scanner scanner = new Scanner(System.in);

	public static void main(String[] args) {
		try (Socket socket = new Socket("127.0.0.1", 8888);
				DataInputStream dis = new DataInputStream(socket.getInputStream());
				DataOutputStream dos = new DataOutputStream(socket.getOutputStream())) {
			
			ClientMessageReceiver messageReceiver = new ClientMessageReceiver(dis);
			new Thread(messageReceiver).start();
			String input = null;
			do {
				input = scanner.nextLine();
				write(dos, input);
			} while (!ChatServer.EXIT.equals(input));
			messageReceiver.stop();
		} catch (IOException e) {
			e.printStackTrace();
		}

	}
	
	private static void write(DataOutputStream dos, String message) throws IOException {
		dos.writeUTF(message);
		dos.flush();
	}

}

运行说明

启动服务器：

启动第一个客户端，输入客户昵称：

服务器监听到了这个事件：

获取所有用户列表，发送给所有用户“hhh”的信息：

服务器端接收到了这个事件：

新的客户端登录，注册用户昵称：

服务器接收到这个事件：

用户1向用户2发送私聊消息：

用户2收到用户1的消息：

客户2向所有用户发送消息：

客户1收到客户2的群发消息：

服务器监听到了这些事件：

客户2退出：

客户1显示的在线列表只有1人了：

客户1也退出：

客户端用户退出的时候，该线程终止。
没客户端用户，服务器也正常跑自己的事。