How to send and receive messages between a modern computer and a Commodore 64 via WiFi?

Question

I want to be able to connect from my Commodore 64 (that has a "wifi modem") to a Linux Raspberry Pi.

The ideal solution would be something like ssh or http clearly but the best I could find is telnet via CCGMS on C64 and write a little python script on the Raspberry side:

#!/usr/bin/env python3

import socket

# Connect to the server with `telnet $HOSTNAME 5000`.

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.setblocking(False)
server.bind((socket.gethostname(), 5000))
server.listen(5)

connections = []

while True:
    try:
        connection, address = server.accept()
        connection.setblocking(False)
        connections.append(connection)
    except BlockingIOError:
        pass

    for connection in connections:
        try:
            message = connection.recv(4096)
            for connection in connections:
                if "commodore".encode() in message:
                    connection.send("Hello, dear C64!\n".encode())
                elif "quit".encode() in message:
                    exit()
                else:
                    connection.send("Which is the magic word?\n".encode())
        except BlockingIOError:
            continue
        except BrokenPipeError:
            continue

This small example works just fine if I connect from another Raspberry Pi. If I connect form the Commodore 64 I can read data that is sent from the Raspberry but I cannot send data from the C64 to the Raspberry. Each time I type a character the Raspberry immediately asks again "Which is the magic word?"

I'd be glad to understand what am I doing wrong and/or receive a better solution to allow the C64 to communicate with the Raspberry Pi.