Python3异步：并行协程意外阻塞

Question

I am trying to get two functions (coroutines) to work in parallel with shared reader, writer streams from a single open network connection like so:

reader, writer = yield from asyncio.open_connection(
                    host, port, ssl=sc, loop=loop)

once the connection is open I can share it in two while loops as follows:

@asyncio.coroutine
def rvcr(loop)
    while True:
        data = yield from reader.readline()
        # do something with it

@asyncio.coroutine
def xmtr(loop)
    while True:
        # get some data
        writer.write(data)

Now I want to schedule these to run in a loop but not block each other. I have read many examples but asyncio is confusing me for some reason.

Some examples show

loop = asyncio.get_event_loop()
asyncio.async(rcvr(loop))
asyncio.async(xmtr(loop))
loop.run_forever()

But the rcvr function blocks and I can't seem to pass reader and writer in correctly. I'm thinking this is a no brainer but for some reason I fail.

Can anyone please help.

Answer 1

Ok I got it working, here is a complete example, the only thing I really need is to find a way to cleanly shut it down on Ctrl-C. This will work with or without ssl encryption.

    #!/usr/bin/python3
"""
    Openssl certifcate and key pairs can be created with the following command:
        openssl req -x509 -newkey rsa:2048 -keyout selfsigned.key -nodes -out selfsigned.cert -sha256 -days 1000
    Store your cert file in the same location as this file.

for testing ssl server
This is like telnet localhost:12345 but using your cert and key
openssl s_client -connect localhost:12345
"""

import os
import sys
import ssl
import asyncio

# --------------------- User configurable settings ---------------------------------
host = '127.0.0.1'
port = 8088
#sslcert = './mycert.cert'
sslcert = None

# ===================== End of user configurable settings ==========================

@asyncio.coroutine
def conn(loop):
    if sslcert != None and not os.path.isfile(sslcert):
        print("You certificate file {} seems to be missing...".format(sslcert))
        sys.exit()

    if sslcert != None:
        sc = ssl.create_default_context(ssl.Purpose.SERVER_AUTH,
            cafile=sslcert)
    else:
        sc=None

    print("Opening connection to {} on port {}...".format(host, port))
    try:
        reader, writer = yield from asyncio.open_connection(
                host, port, ssl=sc, loop=loop)
        print("Connected...")
    except:
        print("Connection Failed, check your host name or IP address and port...")
        sys.exit()

    return reader,writer


@asyncio.coroutine
def rcvr(r):
    print("Dropping into receive loop...")
    while True:
        rsp = yield from r.readline()
        print(rsp)
        yield from asyncio.sleep(.1)


@asyncio.coroutine
def xmtr(w):
    print("Dropping into transmitter loop...")
    while True:
        yield from asyncio.sleep(0.05)  # need this to yield control back to the loop
        w.write("Some data...\n".encode())
        yield from w.drain()


if __name__ == '__main__':
    try:
        loop = asyncio.get_event_loop()
        reader,writer = loop.run_until_complete(conn(loop))
        tasks = [loop.create_task(rcvr(reader)), loop.create_task(xmtr(writer))]
        wait_tasks = asyncio.wait(tasks)
        loop.run_until_complete(wait_tasks)
    except KeyboardInterrupt:
        print("Quiting...")
    finally:
        loop.close()