socketio client throws ConnectionError when can't connect to server (timeout or no route to host) instead of continuously trying to reconnect

[dblitt]

I am trying to have a python client connect to a socket.io server that is resilient to network failure, but I am encountering an issue when the connection times out or when there is no route to host. I would expect the sio client to keep retrying to connect to the server indefinitely, but instead it throws an exception and stops.

Here are the relevant tracebacks:

Traceback (most recent call last):
  File "/home/.../socketClient.py", line 12, in <module>
    sio.connect("http://socket-server:3080")
  File "/home/.../venv/lib/python3.10/site-packages/socketio/client.py", line 338, in connect
    raise exceptions.ConnectionError(exc.args[0]) from None
socketio.exceptions.ConnectionError: HTTPConnectionPool(host='socket-server', port=3080): Max retries exceeded with url: /socket.io/?transport=polling&EIO=4&t=1644461420.8382256 (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f4d47c39fc0>: Failed to establish a new connection: [Errno 113] No route to host'))

Traceback (most recent call last):
  File "/home/.../socketClient.py", line 12, in <module>
    sio.connect("http://socket-server:3080")
  File "/home/.../venv/lib/python3.10/site-packages/socketio/client.py", line 338, in connect
    raise exceptions.ConnectionError(exc.args[0]) from None
socketio.exceptions.ConnectionError: HTTPConnectionPool(host='socket-server', port=3080): Max retries exceeded with url: /socket.io/?transport=polling&EIO=4&t=1644461020.7240138 (Caused by ConnectTimeoutError(<urllib3.connection.HTTPConnection object at 0x7f98f3991fc0>, 'Connection to socket-server timed out. (connect timeout=5)'))

My code is effectively just:

import socketio

sio = socketio.Client()

sio.connect("http://socket-server:3080")

# event handlers here

Is the expected behavior? And if so, what should I do to reach my expected behavior?

[miguelgrinberg]

The Socket.IO client does not retry the initial connection attempt. There is reconnection support, but that kicks in when a previously established connection is lost. For an initial connection, you can build a retry loop on your side.

[dblitt]

Thanks! For anyone else with this issue this is my solution:

sio = socketio.Client()

connected = False
while not connected:
    try:
        sio.connect("http://socket-server:3080")
        print("Socket established")
        connected = True
    except Exception as ex:
        print("Failed to establish initial connnection to server:", type(ex).__name__)
        time.sleep(2)