Possibly the simplest version of a chat server made with Python

simple-asyncio-chat.py

import asyncio

clients = {}

async def handle_new_client(reader, writer):
    writer.write("Welcome to our server!\n".encode('utf-8'))
    peername = '{}:{}'.format(*writer.get_extra_info("peername"))
    clients[peername] = reader, writer
    while True:
        b = await reader.readline()
        if not b:
            del clients[peername]
            return
        for r, w in clients.values():
            w.write("{}: {}".format(peername, b.decode('utf-8')).encode('utf-8'))
            await w.drain()

loop = asyncio.get_event_loop()
server = loop.run_until_complete(asyncio.start_server(handle_new_client, "", 9877))
loop.run_forever()

Usage.md

You can build a client in Python if you feel like it, but you might as well just use telnet:

$ telnet localhost 9877