Simple server that runs a process for each client connection

server.py

#!/usr/bin/env python3.7
# -*- coding: utf-8 -*-

import asyncio
import click

async def copy(src, dst):
    buf = await src.read(1024)
    while buf:
        dst.write(buf)
        await dst.drain()
        buf = await src.read(1024)

async def handle(cmd, reader, writer):
    print('Connection received')
    PIPE = asyncio.subprocess.PIPE
    process = await asyncio.create_subprocess_exec(*cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE)
    await asyncio.gather(copy(reader, process.stdin),
                         copy(process.stdout, writer),
                         copy(process.stderr, writer))

async def start(host, port, cmd):
    server = await asyncio.start_server(lambda r, w: handle(cmd, r, w), host, port)
    async with server:
        await server.serve_forever()

@click.command()
@click.option('-h', '--host', default='127.0.0.1', help='address to bind to')
@click.option('-p', '--port', default=31337, help='port to bind to')
@click.argument('cmd', nargs=-1)
def main(host, port, cmd):
    """Server that spawns a process for each new connection"""
    asyncio.run(start(host, port, cmd))

if __name__ == "__main__":
    main()