如何使用 Java 客户端和 Python 服务器通过套接字创建 IPC？

我试图让两个进程通过本地套接字进行通信：一个 Python服务器和一个 Java客户端。我想在两者之间传递的数据由大小可变的Protobuf对象的字节组成。我希望连接保持打开状态并一直使用到程序结束，因为我传递了很多需要处理的对象。

因为 Protobuf 对象的大小可变，所以我在发送包含该对象的真实消息/响应之前发送消息/响应的大小。

目前，我在 Python 端使用socketserver库中的 TCPServer 。我实现了以下处理程序：

class MyTCPHandler(socketserver.BaseRequestHandler):
    """
    The request handler class for our server.

    It is instantiated once per connection to the server, and must
    override the handle() method to implement communication to the
    client.
    """

    def recv_all(self, n):
        # Helper function to recv n bytes or return None if EOF is hit
        data = b''
        while len(data) < n:
            packet = self.request.recv(n - len(data))
            if not packet:
                return None
            data += packet
        return data

    def handle(self):
        logger.debug("Beginning of handle cycle for client: {}.".format(self.client_address))

        while True:
            if True: # please disregard this if condition
                # Receive 4 bytes (1 int) denoting the size of the message
                data_length_bytes: bytes = self.recv_all(4)
                logger.debug('Received data_length: {}'.format(data_length_bytes))

                # If recv read an empty request b'', then client has closed the connection
                if not data_length_bytes:
                    break

                data_length: int = int.from_bytes(data_length_bytes.strip(), byteorder='big')
                data: bytes = self.recv_all(data_length).strip()

                response: bytes = data.upper()

                # Send length of response first
                self.request.sendall(len(response).to_bytes(4, byteorder='big'))
                # Send response
                self.request.sendall(response)

                logger.debug(
                    'Sent response to: {}. Size of response: {} bytes. Response: {}.'.format(self.client_address,
                                                                                             len(response),
                                                                                             response))


        logger.debug("End of handle cycle for client: {}.".format(self.client_address))

以及以下客户端：

class SocketClient
{
    private static Socket socket;
    private int port;
    private DataOutputStream out;
    private DataInputStream in;

    SocketClient(int port)
    {
        this.port = port;
        this.createSocket();
    }

    private void createSocket() {
        InetAddress address;
        try {
            address = InetAddress.getByName("localhost");
            socket = new Socket(address, port);
            this.out = new DataOutputStream(socket.getOutputStream());
            this.in = new DataInputStream(socket.getInputStream());

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

    byte[] sendMessageAndReceiveResponse(byte[] messageToSend){
        try {
            if(true) {  // again, please disregard this condition
                //Send the size of the message to the server
                this.out.writeInt(messageToSend.length);
                out.flush();

                this.out.write(messageToSend);
                out.flush();

                //Get the response message from the server
                int length = in.readInt();                    // read length of incoming message

                byte[] buffer = null;
                if(length>=0) {
                    buffer = new byte[length];
                    in.readFully(buffer, 0, buffer.length); // read the message
                }

                return buffer;
            }
        }
        catch (ConnectException exception) {
            System.out.println("ATTENTION! Could not connect to socket. Nothing was retrieved from the Python module.");
            exception.printStackTrace();
            return null;
        }
        catch (Exception exception)
        {
            exception.printStackTrace();
            return null;
        }
    }

    void close(){
        //Closing the socket
        try
        {
            in.close();
            out.close();
            socket.close();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    }

我在启动 Python 服务器后运行以下实验：

        SocketClient socketClient = new SocketClient(5000);

        byte[] response;

        // Case 1
        response = socketClient.sendMessageAndReceiveResponse("12345678".getBytes());
        System.out.println(new String(response));

        // Case 2
        response = socketClient.sendMessageAndReceiveResponse("123456781".getBytes());
        System.out.println(new String(response));

        // Case 3
        response = socketClient.sendMessageAndReceiveResponse("12345678123456781".getBytes());
        System.out.println(new String(response));


        socketClient.close();

案例 1 和案例 3 运行良好。但是，当我运行case 2 时，在 Python 服务器端，我得到以下日志：

DEBUG -- [handle()] Received data_length: b'\x00\x00\x00\t' # The '\t' shouldn't be here. A '\x09' should.

然后服务器抛出异常并退出连接。每个 8 < 长度 < 14 的字符串都会发生这种情况。我做错了什么，有没有更简单的方法来实现我想要的？