Python WebSocket Client connecting but not sending messages

Question

While using websocket client to send test messages to a django server, I cannot get a script to work which can both send and receive messages.

The following python script is what I have attempted:

import websocket
import threading
import json
from time import sleep

# handle message event
def on_message(ws, message):
    print("message recieved: %s" % message)

# handle close event
def on_close(ws):
    print("channel closed")

# execute as main script
if __name__ == "__main__":
    websocket.enableTrace(True)
    # new app object connecting to headstation
    ws = websocket.WebSocketApp("ws://192.168.0.106:8000/?testI123", on_message = on_message, on_close = on_close)
    # run in a new thread - kill if script ends
    ws_listener = threading.Thread(target=ws.run_forever())
    ws_listener.daemon = True
    # start second thread
    ws_listener.start()

    # attempt connection 5 times
    timeout = 5
    while not ws.sock.connected and timeout:
        sleep(1)
        timeout -= 1
    # error on timeout
    if (timeout == 0):
        print("Connection to server timed out") 

    print("test 1")
    # periodically send test message to server
    message_num = 0
    while ws.sock.connected:
        # send node id and message
        message = 'hello %d'%message_num
        ws.send(message)
        sleep(1)
        message_num += 1

This connections successfully, indicted by the server, and receives messages sent from the server, but does not send anything.

Periodically, something like this is displayed on the terminal:

send: b'\x8a\x84\xe2\xe9\xa8\xe2\x8f\xdc\xe2\x84'

If I simply use

ws = websocket.WebSocket()
ws.connect(url)
ws.send("hello")

then this works perfectly. Suggesting it is something wrong with my little python script displayed above.

PhilS · Accepted Answer · 2017-12-20 21:10:34Z

1

Found the problem, stupid mistake of course:

 ws_listener = threading.Thread(target=ws.run_forever())

should be:

 ws_listener = threading.Thread(target=ws.run_forever)

without parentheses.

First one passes result of ws.run_forever to the target, second one sets ws.run_forever as the target, which was the intended outcome.

answered Dec 20, 2017 at 21:10

PhilS

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