Java Socket编程从零到实战详解(完整实战案例)

// 步骤1：创建ServerSocket，绑定端口8080
ServerSocket serverSocket = new ServerSocket(8080);
System.out.println("服务端启动，等待连接...");
// 步骤2：等待客户端连接（阻塞方法，直到有客户端连接）
Socket clientSocket = serverSocket.accept(); 
System.out.println("客户端接入：" + clientSocket.getRemoteSocketAddress());
// 步骤3：获取输入流（接收客户端数据）
InputStream input = clientSocket.getInputStream();
byte[] buffer = new byte[1024];
int len = input.read(buffer);  // 读取数据到buffer数组
String receivedData = new String(buffer, 0, len);
System.out.println("收到消息：" + receivedData);
// 步骤4：发送响应数据
OutputStream output = clientSocket.getOutputStream();
output.write("已收到！".getBytes());
// 步骤5：关闭连接（实际开发中需在finally块处理）
clientSocket.close();
serverSocket.close();

// 步骤1：连接服务端（IP+端口）
Socket socket = new Socket("127.0.0.1", 8080);
System.out.println("连接服务端成功！");
// 步骤2：发送数据
OutputStream output = socket.getOutputStream();
output.write("你好，服务端！".getBytes());
// 步骤3：接收响应
InputStream input = socket.getInputStream();
byte[] buffer = new byte[1024];
int len = input.read(buffer);
String response = new String(buffer, 0, len);
System.out.println("服务端响应：" + response);
// 步骤4：关闭连接
socket.close();

Socket socket = new Socket();
// 设置连接超时为5秒（单位：毫秒）
socket.connect(new InetSocketAddress("127.0.0.1", 8080), 5000);  // 

socket.setSoTimeout(3000);  // 设置读取超时3秒 

try (Socket socket = new Socket()) {
    // 连接超时5秒
    socket.connect(new InetSocketAddress("127.0.0.1", 8080), 5000);
    // 读取超时3秒
    socket.setSoTimeout(3000);
    InputStream input = socket.getInputStream();
    // 读取数据...
} catch (SocketTimeoutException e) {
    System.err.println("操作超时：" + e.getMessage());
} catch (IOException e) {
    System.err.println("连接失败：" + e.getMessage());
}

Timer timer = new Timer();
timer.schedule(new TimerTask() {
    @Override
    public void run() {
        try {
            OutputStream out = socket.getOutputStream();
            out.write(0);  // 发送心跳包（内容可为任意约定标识）
            out.flush();
            System.out.println("心跳发送成功");
        } catch (IOException e) {
            System.err.println("心跳发送失败，连接已断开");
            timer.cancel();  // 停止定时任务
        }
    }
}, 0, 30000);  // 立即启动，每30秒执行一次 

socket.setSoTimeout(45000);  // 超时时间略大于心跳间隔
try {
    InputStream in = socket.getInputStream();
    while (true) {
        int data = in.read();  // 阻塞等待数据
        if (data == 0) {
            System.out.println("收到心跳包");
        }
    }
} catch (SocketTimeoutException e) {
    System.err.println("心跳超时，连接断开");
    socket.close();
}

public class EchoServer {
    public static void main(String[] args) throws IOException {
        ExecutorService pool = Executors.newCachedThreadPool();  // 线程池处理并发
        try (ServerSocket server = new ServerSocket(8080)) {
            System.out.println("服务端启动，端口8080");
            while (true) {
                Socket client = server.accept();
                client.setSoTimeout(45000);  // 设置读取超时45秒 
                pool.submit(() -> handleClient(client));
            }
        }
    }
    private static void handleClient(Socket client) {
        try (BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
             PrintWriter out = new PrintWriter(client.getOutputStream(), true)) {
            String input;
            while ((input = in.readLine()) != null) {
                if ("HEARTBEAT".equals(input)) {  // 识别心跳包
                    System.out.println("收到心跳包");
                    continue;
                }
                out.println("Echo: " + input);  // 回显消息
            }
        } catch (SocketTimeoutException e) {
            System.err.println("客户端超时未响应，连接关闭");
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try { client.close(); } catch (IOException e) {}
        }
    }
}

public class EchoClient {
    public static void main(String[] args) {
        try (Socket socket = new Socket()) {
            // 连接超时5秒
            socket.connect(new InetSocketAddress("127.0.0.1", 8080), 5000);
            // 读取超时3秒
            socket.setSoTimeout(3000);
            // 启动心跳线程（每30秒一次）
            startHeartbeat(socket.getOutputStream());
            Scanner scanner = new Scanner(System.in);
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            while (true) {
                System.out.print("输入消息：");
                String msg = scanner.nextLine();
                out.println(msg);  // 发送消息
                System.out.println("服务端响应：" + in.readLine());
            }
        } catch (SocketTimeoutException e) {
            System.err.println("操作超时：" + e.getMessage());
        } catch (IOException e) {
            System.err.println("连接异常：" + e.getMessage());
        }
    }
    private static void startHeartbeat(OutputStream out) {
        Timer timer = new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                try {
                    out.write("HEARTBEAT\n".getBytes());  // 发送心跳标识
                    out.flush();
                } catch (IOException e) {
                    timer.cancel();
                }
            }
        }, 0, 30000);
    }
}