Socket.IO lost connection without knowing?

I'm seeing an issue where the client is losing connection to the server without realizing it.
Here are the logs I'm seeing:

> 2017-03-21 20:40:45,754 - socketIO-client - DEBUG - domain:80/socket.io [engine.io pong] b''
> 2017-03-21 20:41:10,755 - socketIO-client - DEBUG - domain:80/socket.io [engine.io pong] b''
> 2017-03-21 20:41:35,756 - socketIO-client - DEBUG - domain:80/socket.io [engine.io pong] b''
> 2017-03-21 20:42:00,756 - socketIO-client - DEBUG - domain:80/socket.io [engine.io pong] b''
> 2017-03-22 05:51:37,907 - socketIO-client - DEBUG - domain:80/socket.io [socket.io packet sent] 2["message", "16146249067603320215"]
> 2017-03-22 06:52:08,025 - socketIO-client - DEBUG - domain:80/socket.io [socket.io packet sent] 2["message", "16146249067603320215"]
> 2017-03-22 07:52:31,745 - socketIO-client - DEBUG - domain:80/socket.io [socket.io packet sent] 2["message", "16146249067609678438"]
> 2017-03-22 10:27:01,425 - socketIO-client - DEBUG - domain:80/socket.io [engine.io transport selected] websocket
> 2017-03-22 10:27:01,431 - socketIO-client - DEBUG - domain:80/socket.io [engine.io heartbeat reset]
> 2017-03-22 10:27:01,450 - socketIO-client - DEBUG - domain:80/socket.io [engine.io message] b'0'
> 2017-03-22 10:27:01,451 - socketIO-client - DEBUG - domain:80/socket.io [socket.io packet received] b'0'
> 2017-03-22 10:27:01,455 - socketIO-client - DEBUG - domain:80/socket.io [socket.io packet sent] 2["info", "raspberrypi"]

It looks like it's getting pong messages every 25 seconds (all the time before 20:40:45 too) and then it just stops. I just checked the logs this morning at 10:27 and that's when I reset the connection. Now it's all working again.

Any idea why this would happen?