Example of a simple chat room implemented using `asyncio`.

asyncio-chat-server.py

#!/usr/bin/env python3

import asyncio
import sys


class ChatServer:

    def __init__(self, server_name, port, loop):
        self.server_name = server_name
        self.connections = {}
        self.server = loop.run_until_complete(
                asyncio.start_server(
                    self.accept_connection, "", port, loop=loop))


    def broadcast(self, message):
        for reader, writer in self.connections.values():
            writer.write((message + "\n").encode("utf-8"))


    @asyncio.coroutine
    def prompt_username(self, reader, writer):
        while True:
            writer.write("Enter username: ".encode("utf-8"))
            data = (yield from reader.readline()).decode("utf-8")
            if not data:
                return None
            username = data.strip()
            if username and username not in self.connections:
                self.connections[username] = (reader, writer)
                return username
            writer.write("Sorry, that username is taken.\n".encode("utf-8"))


    @asyncio.coroutine
    def handle_connection(self, username, reader):
        while True:
            data = (yield from reader.readline()).decode("utf-8")
            if not data:
                del self.connections[username]
                return None
            self.broadcast(username + ": " + data.strip())


    @asyncio.coroutine
    def accept_connection(self, reader, writer):
        writer.write(("Welcome to " + self.server_name + "\n").encode("utf-8"))
        username = (yield from self.prompt_username(reader, writer))
        if username is not None:
            self.broadcast("User %r has joined the room" % (username,))
            yield from self.handle_connection(username, reader)
            self.broadcast("User %r has left the room" % (username,))
        yield from writer.drain()



def main(argv):

    loop = asyncio.get_event_loop()
    server = ChatServer("Test Server", 4455, loop)
    try:
        loop.run_forever()
    finally:
        loop.close()


if __name__ == "__main__":
    sys.exit(main(sys.argv))

Very useful thank you.

Very useful thank you.

fr

Why is there no client part? I'm a little confused about how the code works