可重复连接的 Socket 服务端与客户端

可支持多客户端的服务器：

1. 当有新连接加入，使用线程池处理连接。

2. 已有连接可重复接收到消息。

public static void main(String[] args) {

    // 创建一个线程池，如果有客户端连接就创建一个线程与之通信
    ExecutorService executorService = Executors.newCachedThreadPool();

    try (ServerSocket serverSocket = new ServerSocket(9999)) {
        while (true) {
            final Socket socket = serverSocket.accept();
            System.out.println("connection...");
            executorService.execute(() -> handle(socket));
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

}

private static void handle(Socket socket) {
    System.out.println("id = " + Thread.currentThread().getId());

    while (!socket.isClosed()) {
        try {
            InputStream inputStream = socket.getInputStream();

            byte[] read = new byte[1024];

            int len = inputStream.read(read);

            String msg = new String(read, 0, len);

            if ("exit".equals(msg)) {
                socket.close();
                break;
            }

            System.out.println("客户端消息：" + msg);

            socket.getOutputStream()
                    .write(("read msg:"+msg).getBytes(StandardCharsets.UTF_8));
        } catch (IOException e) {
            System.out.println("......");
            try {
                socket.close();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

    }

    if (socket.isClosed()) {
        System.out.println("connection closed.");
    }

}

可重复发送消息的客户端：

public static void main(String[] args) {

    try (Socket socket = new Socket("127.0.0.1", 9999)){
        while (true) {
            System.out.print("请输入：");
            Scanner scanner = new Scanner(System.in);

            String line = scanner.nextLine();

            socket.getOutputStream()
                    .write(line.getBytes(StandardCharsets.UTF_8));

            if ("exit".equals(line)) {
                socket.close();
                break;
            }

            byte[] read = new byte[1024];

            int len = socket.getInputStream().read(read);

            System.out.println(new String(read, 0, len));
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}