Java如何实现多线程网络通信

在Java中，可以使用java.net包中的类和接口来实现多线程网络通信。以下是一个简单的示例，展示了如何使用多线程实现一个基本的TCP服务器和客户端。

TCP服务器：

import java.io.*;
import java.net.*;

public class MultiThreadedServer {
    public static void main(String[] args) throws IOException {
        int port = 12345;
        ServerSocket serverSocket = new ServerSocket(port);
        System.out.println("Server is listening on port " + port);

        while (true) {
            Socket socket = serverSocket.accept();
            System.out.println("New client connected");

            ClientHandler clientHandler = new ClientHandler(socket);
            new Thread(clientHandler).start();
        }
    }
}

class ClientHandler implements Runnable {
    private Socket socket;

    public ClientHandler(Socket socket) {
        this.socket = socket;
    }

    @Override
    public void run() {
        try {
            InputStream input = socket.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(input));

            OutputStream output = socket.getOutputStream();
            PrintWriter writer = new PrintWriter(output, true);

            String message;
            while ((message = reader.readLine()) != null) {
                System.out.println("Received message from client: " + message);
                writer.println("Server received: " + message);
            }

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

TCP客户端：

import java.io.*;
import java.net.*;

public class TCPClient {
    public static void main(String[] args) throws IOException {
        String serverAddress = "localhost";
        int port = 12345;

        Socket socket = new Socket(serverAddress, port);
        System.out.println("Connected to server");

        InputStream input = socket.getInputStream();
        BufferedReader reader = new BufferedReader(new InputStreamReader(input));

        OutputStream output = socket.getOutputStream();
        PrintWriter writer = new PrintWriter(output, true);

        BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
        String userInput;

        while ((userInput = stdIn.readLine()) != null) {
            writer.println(userInput);
            String response = reader.readLine();
            System.out.println("Server response: " + response);
        }

        socket.close();
    }
}

在这个示例中，我们创建了一个多线程TCP服务器，它可以同时处理多个客户端连接。每当有新的客户端连接时，服务器都会创建一个新的ClientHandler线程来处理该连接。客户端通过标准输入发送消息，服务器接收消息并将其回显给客户端。

要运行此示例，请首先启动服务器，然后启动一个或多个客户端。服务器将接收来自客户端的消息并将其回显回去。