Java Socket如何实现多线程通信

在Java中，使用Socket实现多线程通信是一种常见的做法。以下是一个简单的示例，展示了如何使用多线程和Socket实现客户端和服务器之间的通信。

1. 首先，创建一个服务器类，该类将监听客户端的连接请求：

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

public class Server {
    public static void main(String[] args) {
        int port = 9999;
        try (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();
            }
        } catch (IOException e) {
            System.out.println("Server exception: " + e.getMessage());
            e.printStackTrace();
        }
    }
}

2. 接下来，创建一个客户端处理类，该类将处理与客户端的通信：

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

public class ClientHandler implements Runnable {
    private Socket socket;

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

    @Override
    public void run() {
        try (
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true)
        ) {
            String message;
            while ((message = in.readLine()) != null) {
                System.out.println("Received from client: " + message);
                out.println("Server received: " + message);
            }
        } catch (IOException e) {
            System.out.println("ClientHandler exception: " + e.getMessage());
            e.printStackTrace();
        } finally {
            try {
                socket.close();
            } catch (IOException e) {
                System.out.println("Could not close socket: " + e.getMessage());
            }
        }
    }
}

3. 最后，创建一个客户端类，该类将连接到服务器并进行通信：

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

public class Client {
    public static void main(String[] args) {
        String host = "localhost";
        int port = 9999;

        try (Socket socket = new Socket(host, port)) {
            BufferedReader userInput = new BufferedReader(new InputStreamReader(System.in));
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            String message;
            while ((message = userInput.readLine()) != null) {
                out.println(message);
                System.out.println("Server response: " + in.readLine());
            }
        } catch (UnknownHostException e) {
            System.out.println("Client exception: " + e.getMessage());
            e.printStackTrace();
        } catch (IOException e) {
            System.out.println("Client exception: " + e.getMessage());
            e.printStackTrace();
        }
    }
}

现在，您可以分别运行服务器和客户端类。服务器将监听端口9999，并在接收到客户端连接时创建一个新的线程来处理通信。客户端将连接到服务器，并允许用户输入消息，这些消息将被发送到服务器并显示服务器的响应。

这只是一个简单的示例，您可以根据需要扩展和修改它以满足您的需求。