如何在Java中实现Socket通信 Java网络编程基础示例

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

public class EchoServer {
    public static void main(String[] args) {
        int port = 12345; // 选择一个未被占用的端口
        System.out.println("Echo服务器正在启动，监听端口: " + port + "...");

        try (ServerSocket serverSocket = new ServerSocket(port)) {
            System.out.println("服务器已启动，等待客户端连接...");
            // serverSocket.accept()会阻塞，直到有客户端连接
            Socket clientSocket = serverSocket.accept();
            System.out.println("客户端已连接: " + clientSocket.getInetAddress().getHostAddress());

            // 获取客户端的输入流和输出流
            try (BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
                 PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true)) { // true表示自动刷新

                String clientMessage;
                // 从客户端读取一行，如果读取到null，表示客户端已关闭连接
                while ((clientMessage = in.readLine()) != null) {
                    System.out.println("收到客户端消息: " + clientMessage);
                    out.println("服务器回声: " + clientMessage); // 将消息回传给客户端
                    if ("bye".equalsIgnoreCase(clientMessage.trim())) {
                        System.out.println("客户端发送'bye'，关闭连接。");
                        break;
                    }
                }
            }
            clientSocket.close(); // 关闭客户端Socket
            System.out.println("客户端连接已关闭。");

        } catch (IOException e) {
            System.err.println("服务器异常: " + e.getMessage());
            e.printStackTrace();
        }
    }
}

import java.io.*;
import java.net.*;
import java.util.Scanner;

public class EchoClient {
    public static void main(String[] args) {
        String serverAddress = "127.0.0.1"; // 服务器IP地址，这里是本机
        int port = 12345; // 服务器监听的端口

        System.out.println("Echo客户端尝试连接服务器: " + serverAddress + ":" + port);

        try (Socket socket = new Socket(serverAddress, port); // 尝试连接服务器
             BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
             PrintWriter out = new PrintWriter(socket.getOutputStream(), true); // 自动刷新
             Scanner scanner = new Scanner(System.in)) {

            System.out.println("成功连接到服务器。输入消息，输入'bye'退出。");

            String userInput;
            while (true) {
                System.out.print("你: ");
                userInput = scanner.nextLine();
                out.println(userInput); // 发送消息给服务器

                if ("bye".equalsIgnoreCase(userInput.trim())) {
                    System.out.println("发送'bye'，准备退出。");
                    break;
                }

                String serverResponse = in.readLine(); // 读取服务器响应
                if (serverResponse == null) {
                    System.out.println("服务器已关闭连接。");
                    break;
                }
                System.out.println("服务器: " + serverResponse);
            }

        } catch (UnknownHostException e) {
            System.err.println("无法找到服务器: " + serverAddress);
        } catch (IOException e) {
            System.err.println("客户端连接或通信异常: " + e.getMessage());
            e.printStackTrace();
        } finally {
            System.out.println("客户端已退出。");
        }
    }
}

// EchoServer的main方法修改版，支持多客户端
public class MultiThreadedEchoServer {
    public static void main(String[] args) {
        int port = 12345;
        System.out.println("多线程Echo服务器正在启动，监听端口: " + port + "...");

        try (ServerSocket serverSocket = new ServerSocket(port)) {
            System.out.println("服务器已启动，等待客户端连接...");
            while (true) { // 服务器会一直运行，等待并处理新连接
                Socket clientSocket = serverSocket.accept(); // 阻塞，直到有新客户端连接
                System.out.println("新客户端已连接: " + clientSocket.getInetAddress().getHostAddress());
                // 为每个新连接创建一个新的线程来处理
                new Thread(new ClientHandler(clientSocket)).start();
            }
        } catch (IOException e) {
            System.err.println("服务器异常: " + e.getMessage());
            e.printStackTrace();
        }
    }
}

// 独立的客户端处理类
class ClientHandler implements Runnable {
    private Socket clientSocket;

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

    @Override
    public void run() {
        try (BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
             PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true)) {

            String clientMessage;
            while ((clientMessage = in.readLine()) != null) {
                System.out.println("从 " + clientSocket.getInetAddress().getHostAddress() + " 收到: " + clientMessage);
                out.println("服务器回声: " + clientMessage);
                if ("bye".equalsIgnoreCase(clientMessage.trim())) {
                    System.out.println(clientSocket.getInetAddress().getHostAddress() + " 发送'bye'，关闭连接。");
                    break;
                }
            }
        } catch (IOException e) {
            System.err.println("客户端 " + clientSocket.getInetAddress().getHostAddress() + " 异常: " + e.getMessage());
        } finally {
            try {
                clientSocket.close();
                System.out.println("客户端 " + clientSocket.getInetAddress().getHostAddress() + " 连接已关闭。");
            } catch (IOException e) {
                System.err.println("关闭Socket时发生错误: " + e.getMessage());
            }
        }
    }
}