[Libwebsockets] Odd "ERR: Ran out of header data space" error?

Bent Bisballe Nyeng deva at aasimon.org
Fri Jun 19 17:20:47 CEST 2020

Hi List

I am making a server based on libwebsockets which serves textual updates
to all connected user based on user input, akin to the drawing example
application; ie. everybody gets notificed about all changes.
My application uses a textual protocol and these messages can sometimes
be ~16kb and above.
The system on which I am developing is based on libwebsocket 2.1 and
everything seem to be working fine.
Recently, however, I deployed the service on a debian server for borader
use, which has libwebsocket 2.0 installed and then I started seeing the
error: "ERR: Ran out of header data space" a lot.
I traced it to the max_http_header_data parameter which in my
application was unset (ie. 0) and increasing it to 16kb seemed to
somewhat mitigate the issue.
I do not, however, understand why I am seeing that error in the first
place, shouldn't that parameter only affect http connections?
I am also not sure why I am seeing the error only on the debian server
and not on my developent PC. Is this perhaps really a bug in 2.0 which
has been fixed in 2.1?

Any advice on the matter will be very much appreciated :-)

Kind regards
Bent Bisballe Nyeng

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