Off-by-one Problem with TCP/IP Client Receive Block and Python Server Sender

Question

When I send the first value from my py server to the Simulink TCP/IP Client Receive block (non-blocking-mode), nothing happens and the data and status outputs both remain 0. When I send the second value, the first value is received. When I send the third, the second is received. And so on. I have no idea why this is happening. Does anyone know how to fix this, or do I need to work around this phenomenon?

[The if-block and data store memory are for handling the non-blocking mode]

Python Server:

import socket
import struct


def start_tcp_server_v3():
    # Initialize socket
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server_socket.settimeout(100)  # Set timeout to 100 seconds as specified in Simulink

    # Bind the socket
    host, port = 'localhost', 50000
    server_socket.bind((host, port))

    while True:
        try:
            # Listen for incoming connections
            server_socket.listen(1)
            print("Server is listening...")

            # Establish connection
            client_socket, client_address = server_socket.accept()
            print(f"Connection established with {client_address}")

            # Reset the timeout for the client socket
            client_socket.settimeout(None)

            while True:
                try:
                    # Get user input for the data to send
                    user_input = input("Please enter a double value to send: ")
                    try:
                        double_value = float(user_input)
                    except ValueError:
                        print("Invalid input. Please enter a valid double value.")
                        continue

                    # Prepare data
                    data = struct.pack('>d', double_value)  # Big-endian byte order, type double

                    # Send data
                    client_socket.sendall(data)
                    print("Just sent: [ "+str(double_value)+" ]")

                except (BrokenPipeError, ConnectionResetError, ConnectionAbortedError):
                    print("Client disconnected. Returning to listening mode.")
                    client_socket.close()  # Close the client socket
                    break  # Break the inner loop to go back to listening for new connections

        except socket.timeout:
            print("Server timeout. No client connected.")
            continue

        except KeyboardInterrupt:
            print("Server is shutting down.")
            break

        finally:
            # Close client socket if it exists
            if 'client_socket' in locals():
                client_socket.close()

    # Close the server socket
    server_socket.close()
    print("Server has been closed.")

# -----------------------------------------

start_tcp_server_v3()