The underlying connection was closed before the hub handshake could complete

[Lohit Bura]

I implemented the code . It's Working in some devices . But In Some of the devices it's showing the following error .
I guess the main reason is that connection is not establishing.

"The underlying connection was closed before the hub handshake could complete"

[clmorales]

I was having the same issue and I managed to fixed it setting the transport in options to LongPolling

hubConnection = HubConnectionBuilder()
.withUrl(serverUrl,
options: HttpConnectionOptions(
transport: HttpTransportType.LongPolling,
))

[chenshaxuanjing]

same issues, any solution?

[chrcao]

hi @sefidgaran
any solution to fix this problem?

[Farshid Sefidgaran]

I was having the same issue and I managed to fixed it setting the transport in options to LongPolling

hubConnection = HubConnectionBuilder() .withUrl(serverUrl, options: HttpConnectionOptions( transport: HttpTransportType.LongPolling, ))

Hi @chrcao
Have you tried the solution above?

[chrcao]

hi @sefidgaran
it is not working.

[MathiasTP]

I can confirm that i get the error aswell. I am on flutter 3.0.0.
If i try to use the transport option longpolling i will get an error aswell.

[aminesnip]

I am getting this error as well.
When I test locally on windows it works very well, but the error appears when I publish on the linux server.
Any solution to fix this problem ?.

[dumptyhumpty2014gmail]

In my case I set correct port that solved this problem

[ingvilow]

I was struggiling with the same ussue, but in my case API-devs created accessToken to API and I used it wrong. So as I understood SignalR package put in headers access tokens and if your API-devs configure token as "&authinticate=tokens_long_string_key_example", it is not gonna work, because server can't negotiate (I didn't remember verbatim the error in this case, but it will be something about negotiation). In my case to resolve this issue I should have in request body access-token instead of authinticate. Also really highly reccomend to use this Logger package logging: any, it is real time-saver

[ycy]

In my case, it's the Authorization that caused this problem, in detail, every step needs to add Authorization in the header including during websocket handshaking. Hope this would help.