Extremely simple "distributed echo server" server in Python (Telnet clients should be able to connect to it).

telnet.py

#!/usr/bin/env python3

import socket

# Read "distributed echo server" as "(distributed echo) server". The "server"
# is not "distributed" but the echos are "distributed" to every connected
# client.

# Connect to the server with `telnet localhost 5000`.

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.setblocking(False)
server.bind(('localhost', 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)
        except BlockingIOError:
            continue

        for connection in connections:
            connection.send(message)

This isn't Telnet, this is an Echo server (plus distribution of messages to all connected clients).

Fair enough. I'll update the description.

Session stopped
- Press to exit tab
- Press R to restart session
- Press S to save terminal output to file

Network error: Connection refused

telnet.exe 127.0.0.1 5000
Trying 127.0.0.1...                     
                                                                                                                          
telnet: Unable to connect to remote host: Connection refused                

@QGB you are trying to connect to localhost but the script was binding your host name. I changed it to bind to localhost, so telnet localhost 5000 should work as expected.