aio chat client and server examples

00_README.md

This is a simple implementation for TCP server and client. The server listens for the port 9090 of the localhost, receives messages from any connected clients, and sends them to all connected peers. The client is started with a username as an argument, reads in an infinite loop messages from the string, re-format them as "name > message\n" and send to the server. In a different async function it also waits for message from the server and prints the to the console.

Files:

• aio_chat_client.py: client implementation
• aio_chat_server.py: server implementation

Dependencies: Python 3.6+ and aioconsole

Install aioconsole

pip install aioconsole

Start server as this:

python ./aio_chat_server.py

Start two clients in separate consoles as

python ./aio_chat_server.py Foo

and

python ./aio_chat_server.py Bar

Try to write a message in any console.

More info:

• asyncio echo client and server
• aioconsole. The documentation is unfortunately not very complete, but it seems to work, and should also work under Windows
• simplified introduction into asyncio

aio_chat_client.py

import sys
import asyncio

from aioconsole import ainput, aprint

writer = None
my_name = sys.argv[1]


async def main():
    await asyncio.gather(network(), console())


async def network():
    global writer
    reader, writer = await asyncio.open_connection('127.0.0.1', 9090)
    while not reader.at_eof():
        data = await reader.readline()
        await aprint(data.decode('utf-8'), end='')
    writer.close()


async def console():
    while True:
        message = await ainput('')
        formatted = f'{my_name} > {message}\n'
        if writer:
            writer.write(formatted.encode('utf-8'))
            await writer.drain()


loop = asyncio.get_event_loop()
loop.run_until_complete(main())
loop.close()

aio_chat_server.py

import asyncio

# Global list of clients. Each of those clients is a "writer" object, which
# we will use to send message to peers
clients = []


async def start_server():
    """
    Async function to start the server
    """
    await asyncio.start_server(handle_messages, '127.0.0.1', 9090)


async def handle_messages(reader, writer):
    """
    The handler. Every time new client is connected to the server, a new
    async handler is initiated with a (reader, writer) pair
    """
    print('Someone connected')
    # Add the client to the list
    clients.append(writer)

    # Asynchronously read messages from the client until it
    # closes the connection
    while not reader.at_eof():
        message = await reader.readline()

        # send message to each of the peers
        for writer in clients:
            if not writer.is_closing():
                writer.write(message)
                await writer.drain()

    print('Someone disconnected')
    writer.close()


loop = asyncio.get_event_loop()
# start the server and wait while the connection is established
loop.run_until_complete(start_server())
# process incoming messages until Ctrl+C is pressed
loop.run_forever()