Example of driving transfers with pycurl's multi.socket_action

pycurl_multi_socket_action.py

import asyncio
import pycurl
import selectors


MULTI = pycurl.CurlMulti()
SELECTOR = selectors.DefaultSelector()
LOOP = asyncio.get_event_loop()
TIMER = None


def socket_function(event, socket, multi, data):
    print(f'\033[95msocket_function: event={event}, socket={socket}\033[0m')
    if event == pycurl.POLL_REMOVE:
        SELECTOR.unregister(socket)
    else:
        try:
            SELECTOR.register(socket, event)
        except KeyError:
            SELECTOR.modify(socket, event)

def socket_timeout():
    print(f'\033[92msocket_timeout\033[0m')
    return MULTI.socket_action(pycurl.SOCKET_TIMEOUT, 0)

def timer_function(timeout_ms):
    global TIMER
    print(f'\033[96mtimer_function: {timeout_ms}\033[0m')
    if timeout_ms == -1:
        TIMER.cancel()
    else:
        TIMER = LOOP.call_later(timeout_ms / 1000, socket_timeout)
    return 0

def write_function(data):
    print(f'\033[93mwrite_function: {data}\033[0m')


async def main():
    # set callbacks for driving with multi-socket-action
    MULTI.setopt(pycurl.M_SOCKETFUNCTION, socket_function)
    MULTI.setopt(pycurl.M_TIMERFUNCTION, timer_function)
    # init easy
    easy = pycurl.Curl()
    easy.setopt(pycurl.WRITEFUNCTION, write_function)
    easy.setopt(pycurl.VERBOSE, 1)
    easy.setopt(pycurl.URL, 'https://nghttp2.org/httpbin/drip?duration=1&numbytes=10&code=200&delay=1')
    # the following should call timer_function which would start the transfer
    MULTI.add_handle(easy)
    await asyncio.sleep(0)
    run_count = 1
    # but have to init the transfer explicitly
    _, run_count = socket_timeout()
    # drive the transfer with multi-socket-action
    while run_count:
        await asyncio.sleep(0)
        for key, event in SELECTOR.select(timeout=None):
            await asyncio.sleep(0)
            _, run_count = MULTI.socket_action(key.fd, event)
    # close easy
    easy.close()
    MULTI.remove_handle(easy)


LOOP.run_until_complete(main())
MULTI.close()
SELECTOR.close()