Twisted reactor 循环如何知道它应该调用 recv 以及它如何知道要调用哪个函数？

Question

我正在测试一个扭曲的客户端服务器。有三台相同的服务器，每台都通过 sendall() 发送大量数据。有一个客户端实现了一个reactor，接收数据如下：

Task 1: got 60 bytes of poetry from 127.0.0.1:10000
Task 2: got 10 bytes of poetry from 127.0.0.1:10001
Task 3: got 10 bytes of poetry from 127.0.0.1:10002
Task 1: got 30 bytes of poetry from 127.0.0.1:10000
Task 3: got 10 bytes of poetry from 127.0.0.1:10002
Task 2: got 10 bytes of poetry from 127.0.0.1:10001
...
Task 1: 3003 bytes of poetry
Task 2: 623 bytes of poetry
Task 3: 653 bytes of poetry
Got 3 poems in 0:00:10.134220

我对客户端如何知道（1）在poetry_main() 中执行for 循环直到接收到所有数据感到困惑，即使每次客户端从服务器接收到一小块数据后都会出现socket.error（ 2）使用doRead函数；除了在类函数定义中之外，它在任何地方都没有被引用。如果有人能解释这一点，那就太好了！

客户

# This is the Twisted Get Poetry Now! client, version 1.0.

# NOTE: This should not be used as the basis for production code.
# It uses low-level Twisted APIs as a learning exercise.

import datetime, errno, optparse, socket

from twisted.internet import main


def parse_args():
    usage = """usage: %prog [options] [hostname]:port ...

This is the Get Poetry Now! client, Twisted version 1.0.
Run it like this:

  python get-poetry.py port1 port2 port3 ...

If you are in the base directory of the twisted-intro package,
you could run it like this:

  python twisted-client-1/get-poetry.py 10001 10002 10003

to grab poetry from servers on ports 10001, 10002, and 10003.

Of course, there need to be servers listening on those ports
for that to work.
"""

    parser = optparse.OptionParser(usage)

    _, addresses = parser.parse_args()

    if not addresses:
        print parser.format_help()
        parser.exit()

    def parse_address(addr):
        if ':' not in addr:
            host = '127.0.0.1'
            port = addr
        else:
            host, port = addr.split(':', 1)

        if not port.isdigit():
            parser.error('Ports must be integers.')

        return host, int(port)

    return map(parse_address, addresses)


class PoetrySocket(object):

    poem = ''

    def __init__(self, task_num, address):
        self.task_num = task_num
        self.address = address
        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.sock.connect(address)
        self.sock.setblocking(0)

        # tell the Twisted reactor to monitor this socket for reading
        from twisted.internet import reactor
        reactor.addReader(self)

    def fileno(self):
        try:
            return self.sock.fileno()
        except socket.error:
            return -1

    def connectionLost(self, reason):
        self.sock.close()

        # stop monitoring this socket
        from twisted.internet import reactor
        reactor.removeReader(self)

        # see if there are any poetry sockets left
        for reader in reactor.getReaders():
            if isinstance(reader, PoetrySocket):
                return

        reactor.stop() # no more poetry

    def doRead(self):
        bytes = ''
        count = 0

        while True:
            count += 1
            try:
                bytesread = self.sock.recv(1024)
                if not bytesread:
                    break
                else:
                    bytes += bytesread
                    print ('bytesread read: ', bytes)
            except socket.error, e:
                if e.args[0] == errno.EWOULDBLOCK:
                    break
                return main.CONNECTION_LOST

            print ('count read: ', count)

        print ('task? : ', bytes)
        if not bytes:
            print 'Task %d finished' % self.task_num
            return main.CONNECTION_DONE
        else:
            msg = 'Task %d: got %d bytes of poetry from %s'
            print  msg % (self.task_num, len(bytes), self.format_addr())

        self.poem += bytes

    def logPrefix(self):
        return 'poetry'

    def format_addr(self):
        host, port = self.address
        return '%s:%s' % (host or '127.0.0.1', port)


def poetry_main():
    addresses = parse_args()

    start = datetime.datetime.now()

    sockets = [PoetrySocket(i + 1, addr) for i, addr in enumerate(addresses)]

    from twisted.internet import reactor
    reactor.run()

    elapsed = datetime.datetime.now() - start

    for i, sock in enumerate(sockets):
        print 'Task %d: %d bytes of poetry' % (i + 1, len(sock.poem))

    print 'Got %d poems in %s' % (len(addresses), elapsed)


if __name__ == '__main__':
    poetry_main()

服务器

# This is the blocking version of the Slow Poetry Server.

import optparse, os, socket, time


def parse_args():
    usage = """usage: %prog [options] poetry-file

This is the Slow Poetry Server, blocking edition.
Run it like this:

  python slowpoetry.py <path-to-poetry-file>

If you are in the base directory of the twisted-intro package,
you could run it like this:

  python blocking-server/slowpoetry.py poetry/ecstasy.txt

to serve up John Donne's Ecstasy, which I know you want to do.
"""

    parser = optparse.OptionParser(usage)

    help = "The port to listen on. Default to a random available port."
    parser.add_option('--port', type='int', help=help)

    help = "The interface to listen on. Default is localhost."
    parser.add_option('--iface', help=help, default='localhost')

    help = "The number of seconds between sending bytes."
    parser.add_option('--delay', type='float', help=help, default=.7)

    help = "The number of bytes to send at a time."
    parser.add_option('--num-bytes', type='int', help=help, default=10)

    options, args = parser.parse_args()

    if len(args) != 1:
        parser.error('Provide exactly one poetry file.')

    poetry_file = args[0]

    if not os.path.exists(args[0]):
        parser.error('No such file: %s' % poetry_file)

    return options, poetry_file


def send_poetry(sock, poetry_file, num_bytes, delay):
    """Send some poetry slowly down the socket."""

    inputf = open(poetry_file)

    while True:
        bytes = inputf.read(num_bytes)

        if not bytes: # no more poetry :(
            sock.close()
            inputf.close()
            return

        print 'Sending %d bytes' % len(bytes)

        try:
            sock.sendall(bytes) # this is a blocking call
        except socket.error:
            sock.close()
            inputf.close()
            return

        time.sleep(delay)


def serve(listen_socket, poetry_file, num_bytes, delay):
    while True:
        sock, addr = listen_socket.accept()

        print 'Somebody at %s wants poetry!' % (addr,)

        send_poetry(sock, poetry_file, num_bytes, delay)


def main():
    options, poetry_file= parse_args()

    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.bind((options.iface, options.port or 0))

    sock.listen(5)

    print 'Serving %s on port %s.' % (poetry_file, sock.getsockname()[1])

    serve(sock, poetry_file, options.num_bytes, options.delay)


if __name__ == '__main__':
    main()

Answer 1

找到它here！该类实现了一个接口，其功能是事件驱动循环的一部分。