[Libwebsockets] Sending WS Connection Close packet immediately from the lws client

Brice Hamon brice at ydotm.com
Tue May 21 15:23:38 CEST 2019

I have done this on my side.
The client sends "I want go close", the server responds "Ok" and knows that
client is going away.
I request a WRITE to it and when I get lws notification, I return -1 which
kills the connection.

On Tue, May 21, 2019 at 9:20 AM Andy Green <andy at warmcat.com> wrote:

> On 5/21/19 2:17 PM, Mateusz Stępień wrote:
> > On 5/21/19 2:51 PM, Andy Green wrote:
> >  > There's also this api
> >  >
> >  >
> >
> https://libwebsockets.org/git/libwebsockets/tree/include/libwebsockets/lws-timeout-timer.h#n79-105
> >
> >
> > That function would probably help, when I could get to the point that
> > Close message is already sent and I'm waiting for ACK from the server.
> >
> >> You can never guarantee you can either send the close frame at all or
> >> when you can send it.
> >
> > That can be said about every packet going out from the client. However
> > the issue is not about flaky connection or sth like that. It is that
> > that I cannot send Close message like I can send any other one. Right
> ws close frame is handled by lws internally, yes.
> > now if I want to close the connection with a close message and a chosen
> > reason, I need to wait for the CLIENT_RECEIVE callback and because I
> No... you just need to let know lws you want to close that wsi... the
> api I linked to will allow you to do that from any callback.
> > cannot force it, I am at the mercy of server, which can send another
> > message in 5 seconds, or in 20 minutes, or never. Please note, that I'm
> > talking about time between setting "completed" flag and receiving
> > CLIENT_RECEIVE callback.
> >
> >> If it can be sent within a timeout period of a few seconds, it will be
> >> sent.  But anything can crash or run out of battery or lose connection
> >> at any time without ceremony.  So you shouldn't assume this can be
> >> made a certainty... CLOSE callback to learn the socket closed is much
> >> more certain.
> >
> > I'm sorry, but I don't see the relevance to my issue. At the CLOSE
> > callback there's nothing I can do to send the Close message.
> You seem to be setting flags and stuff like you're going to rely on it.
> It spells it out in RFC6455, you can't rely on the CLOSE frames coming.
> -Andy
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