Simple echo server (with pretzel framework)

pretzel_echo.py

"""Simple echo server

pretzel framework: https://github.com/aslpavel/pretzel
"""
from __future__ import print_function
import sys
import socket
from pretzel.app import app
from pretzel.monad import async
from pretzel.uniform import BrokenPipeError
from pretzel.stream import BufferedSocket


@async
def client_coro(sock, addr):
    """Client coroutine
    """
    try:
        print('[+clinet] fd:{} addr:{}'.format(sock.fileno(), addr))
        while True:
            data = yield sock.read(1024)  # receive data (throws an error if data is b'')
            sock.write_schedule(data)     # schedule data to be written
            yield sock.flush()            # flush buffered data
    except BrokenPipeError:
        pass
    finally:
        print('[-client] fd:{} addr:{}'.format(sock.fileno(), addr))
        sock.dispose()  # close client socket (with context may be used)


@async
def server_coro(host, port):
    """Server coroutine
    """
    with BufferedSocket(socket.socket()) as sock:  # create async socket
        sock.bind(('127.0.0.1', port))             # just bind
        sock.listen(10)                            # just listen
        print('[server] {}:{}'.format(host, port))
        while True:
            client, addr = yield sock.accept()  # asynchronously accept connection
            client_coro(client, addr)()         # start client coroutine (background)


@app
def main():
    if len(sys.argv) < 2:
        sys.stderr.write('usage: {} <port>\n'.format(sys.argv[0]))
        sys.exit(1)
    yield server_coro('localhost', int(sys.argv[1]))  # wait for server coroutine

if __name__ == '__main__':
    main()