Python async TCP server: cannot get sockets from it

Question

I'm trying to simulate a network using asychronious TCP servers and sockets. I used an example from documentation as a starting point for my task. Here's the code of my server class:

import asyncio
import socket
import Node

class ServerProtocol(asyncio.Protocol):
    def __init__(self, hostNode):
        self.hostNode = hostNode

    def connection_made(self, transport):
        peername = transport.get_extra_info('peername')
        print('Connection from {}'.format(peername))
        self.transport = transport

    def data_received(self, data):
        print('Data received: {!r}'.format(data))
        self.hostNode.processIncomingMessage(data)

class NodeServer:
    def __init__(self, hostNode):
        self.loop = asyncio.get_event_loop()
        self.hostNode = hostNode

    def startListening(self):
        self.coro = self.loop.create_server(ServerProtocol(self.hostNode), '', 0, family=socket.AF_INET)
        server = self.loop.run_until_complete(self.coro)

    def getPortNumber(self):
        print(self.coro.sockets)
        portNumber = self.coro.sockets[0].getpeername()[1]
        print(portNumber)
        return portNumber

I call create_server function with params '', 0 and family=socket.AF_INET because I need to establish IPv4 version and the OS must give appropriate random port to listen. In the code below I'm trying to get a number of port. Documentation says, create_server function returns Server object, and sockets can be retrieved from sockets attribute. But when I run the code, I get following error:

AttributeError: 'generator' object has no attribute 'sockets'

It happens when executing self.coro.sockets

So, that's the issue.

Could someone help me with this, please?

Many thanks.

user85442 · Accepted Answer · 2016-05-28 19:22:46Z

1

The call to create_server returns a coroutine. The server instance which has the sockets attribute is returned when you call run_until_complete. Change the definition of startListening to save the return value of run_until_complete as self.server and modify your getPortNumber definition to use that instead. You also need to change getpeername to getsockname to get the port allocated.

class NodeServer:
    def __init__(self, hostNode):
        self.loop = asyncio.get_event_loop()
        self.hostNode = hostNode

    def startListening(self):
        self.coro = self.loop.create_server(ServerProtocol(self.hostNode), '', 0, family=socket.AF_INET)
        self.server = self.loop.run_until_complete(self.coro)

    def getPortNumber(self):
        print(self.server.sockets)
        portNumber = self.server.sockets[0].getsockname()[1]
        print(portNumber)
        return portNumber

answered May 28, 2016 at 19:22

user85442

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1 Comment

gsa Over a year ago

Thanks. It really hepled. Can I ask you another question?

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