Issues listening incoming messages in websocket client on Python 3.6

Question

I’m trying to build a websocket client on Python using websockets package from here: Websockets 4.0 API

I’m using this way instead of example code because I want to create a websocket client class object, and use it as gateway.

I’m having issues with my listener method (receiveMessage) on client side, which raises a ConnectionClose exception at execution. I think maybe there is any problem with the loop.

This is the simple webSocket client I’ve tried to build:

import websockets

class WebSocketClient():

    def __init__(self):
        pass

    async def connect(self):
        '''
            Connecting to webSocket server

            websockets.client.connect returns a WebSocketClientProtocol, which is used to send and receive messages
        '''
        self.connection = await websockets.client.connect('ws://127.0.0.1:8765')
        if self.connection.open:
            print('Connection stablished. Client correcly connected')
            # Send greeting
            await self.sendMessage('Hey server, this is webSocket client')
            # Enable listener
            await self.receiveMessage()


    async def sendMessage(self, message):
        '''
            Sending message to webSocket server
        '''
        await self.connection.send(message)

    async def receiveMessage(self):
        '''
            Receiving all server messages and handling them
        '''
        while True:
            message = await self.connection.recv()
            print('Received message from server: ' + str(message))

And this is the main:

'''
    Main file
'''

import asyncio
from webSocketClient import WebSocketClient

if __name__ == '__main__':
    # Creating client object
    client = WebSocketClient()
    loop = asyncio.get_event_loop()
    loop.run_until_complete(client.connect())
    loop.run_forever()
    loop.close()

To test incoming messages listener, server sends two messages to client when it stablishes the connection.

Client connects correctly to server, and sends the greeting. However, when client receives both messages, it raises a ConnectionClosed exception with code 1000 (no reason).

If I remove the loop in the receiveMessage client method, client does not raise any exception, but it only receives one message, so I suppose I need a loop to keep listener alive, but I don’t know exactly where or how.

Any solution?

Thanks in advance.

EDIT: I realize that client closes connection (and breaks loop) when it receives all pending messages from server. However, I want client keeps alive listening future messages.

In addition, I’ve tried to add another function whose task is to send a ‘heartbeat’ to server, but client closes connection anyway.

Asked By: CharlieHollow

||

Source

Answer 1

Finally, based on this post answer, I modified my client and main files this way:

WebSocket Client:

import websockets
import asyncio

class WebSocketClient():

    def __init__(self):
        pass

    async def connect(self):
        '''
            Connecting to webSocket server

            websockets.client.connect returns a WebSocketClientProtocol, which is used to send and receive messages
        '''
        self.connection = await websockets.client.connect('ws://127.0.0.1:8765')
        if self.connection.open:
            print('Connection stablished. Client correcly connected')
            # Send greeting
            await self.sendMessage('Hey server, this is webSocket client')
            return self.connection


    async def sendMessage(self, message):
        '''
            Sending message to webSocket server
        '''
        await self.connection.send(message)

    async def receiveMessage(self, connection):
        '''
            Receiving all server messages and handling them
        '''
        while True:
            try:
                message = await connection.recv()
                print('Received message from server: ' + str(message))
            except websockets.exceptions.ConnectionClosed:
                print('Connection with server closed')
                break

    async def heartbeat(self, connection):
        '''
        Sending heartbeat to server every 5 seconds
        Ping - pong messages to verify connection is alive
        '''
        while True:
            try:
                await connection.send('ping')
                await asyncio.sleep(5)
            except websockets.exceptions.ConnectionClosed:
                print('Connection with server closed')
                break

Main:

import asyncio
from webSocketClient import WebSocketClient

if __name__ == '__main__':
    # Creating client object
    client = WebSocketClient()
    loop = asyncio.get_event_loop()
    # Start connection and get client connection protocol
    connection = loop.run_until_complete(client.connect())
    # Start listener and heartbeat 
    tasks = [
        asyncio.ensure_future(client.heartbeat(connection)),
        asyncio.ensure_future(client.receiveMessage(connection)),
    ]

    loop.run_until_complete(asyncio.wait(tasks))

Now, client keeps alive listening all messages from server and sending ‘ping’ messages every 5 seconds to server.

Answered By: CharlieHollow

Issues listening incoming messages in websocket client on Python 3.6

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