sometimes get an error : future was called on null at hubconnection.start(). In the line await _handshakeCompleter.future

[Adilkp796]

Some times get error in hubconnection.start() method with a message future was called on null .The error is exactly on _handshakeCompleter.future .How can resolve it ??

[Schaeri]

We have the same problem (Version 0.1.5). I look at the code and see the following problem:
In the start method of the class HubConnection the completer gets instantiated on line 102. After that the code await for the start of the connection. During this period the method _processHandshakeResponse gets called and set the _handshakeCompleter to null. Then the await on line 117 will fail with a null reference exception.
The simplest fix for that is to make a null check on line 117. But I can not say if that is correct.
Are there any plans to fix this issue soon?

[davbaron]

I am getting the same issue, though it is intermittent, meaning, sometimes it throws the error (null _handshakeCompleter) and sometimes it works. I will post a separate issue on my overall issue (client and/or server not working). I cannot discern a pattern of failure. I would like to say that it 'usually' happens while my VS 2019 project is in run/debug mode, but I can't say exactly what percentage 'usually' is. It certainly fails when not debugging as well. The issue is not, at least for me, binary either - besides either connecting successfully or failing with a null _handshakeCompleter, I also get failures for 404 (remote server not found). This is with no changes to code. The same code that succeeds will then fail with a 404, which is somewhat hard to understand.

I will also add however, that even when it does work, and I 'print' out the successful connected state, when I 'close' the Flutter screen (go back to a prior screen), I never get an 'immediate' print out of 'connection closed'. Instead I have added the dispose() method to my screen, and if the connection is 'Connected' then I issue a .stop() call. Seems to work.

[firatcetiner]

Same issue here. Following the exact instruction as the Example Project.

[digitalkirkley]

I get same intermittent issue. To resolve (hub_connection line: 117):
if (_handshakeCompleter != null)
await _handshakeCompleter.future;
This seems to work.

[KThen]

I've never worked with SignalR before but I'm curious, is this an issue to be solved, or does it only occur during flutter restart/hot reload? If it only happens during flutter restart/hot reload I'm not that worried, but if it will occur during production then I would like to know what the proper solution is.

I am trying to evaluate @digitalkirkley 's solution but I'm not sure tampering with the source code is the right way.

[firatcetiner]

I got this error roughly 6 months ago and back then I quit using SignalR and started to build my own solution with basic socket programming. However, after a long while I decided to give an another chance to SignalR and now it's working like a charm. If this issue still occures, I think it doesn't related to this package at all.