Sto cercando di capire come funziona il modulo Python 3 asyncio
, in particolare utilizzando l'API di trasporto/protocollo. Voglio creare un modello di pubblicazione/sottoscrizione e utilizzare la classe asyncio.Protocol
per creare il mio client e il mio server.Classe di protocollo client persistente Asyncio utilizzando la coda
Al momento il server è attivo e in esecuzione e sta ascoltando le connessioni client in entrata. Il client è in grado di connettersi al server, inviare un messaggio e ricevere la risposta.
Mi piacerebbe essere in grado di mantenere in vita la connessione TCP e mantenere una coda che mi permetta di aggiungere messaggi. Ho provato a trovare un modo per farlo usando l'API di basso livello (Transport/Protocols) ma i documenti/gli asyncio limitati online sembrano tutti entrare nell'API di alto livello - usando i flussi, ecc. Qualcuno potrebbe essere in grado di indicarmi la giusta direzione su come implementarlo?
Ecco il codice del server:
#!/usr/bin/env python3
import asyncio
import json
class SubscriberServerProtocol(asyncio.Protocol):
""" A Server Protocol listening for subscriber messages """
def connection_made(self, transport):
""" Called when connection is initiated """
self.peername = transport.get_extra_info('peername')
print('connection from {}'.format(self.peername))
self.transport = transport
def data_received(self, data):
""" The protocol expects a json message containing
the following fields:
type: subscribe/unsubscribe
channel: the name of the channel
Upon receiving a valid message the protocol registers
the client with the pubsub hub. When succesfully registered
we return the following json message:
type: subscribe/unsubscribe/unknown
channel: The channel the subscriber registered to
channel_count: the amount of channels registered
"""
# Receive a message and decode the json output
recv_message = json.loads(data.decode())
# Check the message type and subscribe/unsubscribe
# to the channel. If the action was succesful inform
# the client.
if recv_message['type'] == 'subscribe':
print('Client {} subscribed to {}'.format(self.peername,
recv_message['channel']))
send_message = json.dumps({'type': 'subscribe',
'channel': recv_message['channel'],
'channel_count': 10},
separators=(',', ':'))
elif recv_message['type'] == 'unsubscribe':
print('Client {} unsubscribed from {}'
.format(self.peername, recv_message['channel']))
send_message = json.dumps({'type': 'unsubscribe',
'channel': recv_message['channel'],
'channel_count': 9},
separators=(',', ':'))
else:
print('Invalid message type {}'.format(recv_message['type']))
send_message = json.dumps({'type': 'unknown_type'},
separators=(',', ':'))
print('Sending {!r}'.format(send_message))
self.transport.write(send_message.encode())
def eof_received(self):
""" an EOF has been received from the client.
This indicates the client has gracefully exited
the connection. Inform the pubsub hub that the
subscriber is gone
"""
print('Client {} closed connection'.format(self.peername))
self.transport.close()
def connection_lost(self, exc):
""" A transport error or EOF is seen which
means the client is disconnected.
Inform the pubsub hub that the subscriber has
Disappeared
"""
if exc:
print('{} {}'.format(exc, self.peername))
loop = asyncio.get_event_loop()
# Each client will create a new protocol instance
coro = loop.create_server(SubscriberServerProtocol, '127.0.0.1', 10666)
server = loop.run_until_complete(coro)
# Serve requests until Ctrl+C
print('Serving on {}'.format(server.sockets[0].getsockname()))
try:
loop.run_forever()
except KeyboardInterrupt:
pass
# Close the server
try:
server.close()
loop.until_complete(server.wait_closed())
loop.close()
except:
pass
Ed è il codice del client qui:
#!/usr/bin/env python3
import asyncio
import json
class SubscriberClientProtocol(asyncio.Protocol):
def __init__(self, message, loop):
self.message = message
self.loop = loop
def connection_made(self, transport):
""" Upon connection send the message to the
server
A message has to have the following items:
type: subscribe/unsubscribe
channel: the name of the channel
"""
transport.write(self.message.encode())
print('Message sent: {!r}'.format(self.message))
def data_received(self, data):
""" After sending a message we expect a reply
back from the server
The return message consist of three fields:
type: subscribe/unsubscribe
channel: the name of the channel
channel_count: the amount of channels subscribed to
"""
print('Message received: {!r}'.format(data.decode()))
def connection_lost(self, exc):
print('The server closed the connection')
print('Stop the event loop')
self.loop.stop()
if __name__ == '__main__':
message = json.dumps({'type': 'subscribe', 'channel': 'sensor'},
separators=(',', ':'))
loop = asyncio.get_event_loop()
coro = loop.create_connection(lambda: SubscriberClientProtocol(message,
loop),
'127.0.0.1', 10666)
loop.run_until_complete(coro)
try:
loop.run_forever()
except KeyboardInterrupt:
print('Closing connection')
loop.close()
Grazie a @dano per la risposta rapida e completa. Ho applicato le modifiche al mio codice e funziona come un incantesimo! – thiezn
@dano Grazie mille. Questo è esattamente quello che ho cercato. – user24502