A problem involving threads and http streams

Dear all,

In connection with my work on Pengine I have run into an issue I don't
understand.

The help you see the problem I have attached a zip archive with three
small files, two servers and one client:

test_server_buggy.pl
test_server_working.pl
test_client.pl

The difference between test_server_working.pl and test_server_buggy.pl
is very small. In test_server_working.pl I use a message queue with a
hard coded name 'out'. This works but isn't good enough since my
application requires that the name of the message queue is unique. In
test_server_buggy.pl I use http_session_assert/1 and
http_session_data/1 to remember the unique message queue name as given
by message_queue_create/1. This doesn't work, since an error

error(existence_error(stream,<stream>(0x7fb2d9201fb0)),context(http_stream:is_cgi_stream/1,_G132))

is thrown. I don't understand why this happens and how to work around it.

I use the latest SWI Prolog developer version on a Mac.

Best regards,
Torbjörn

-- 
Torbjörn Lager
Professor of General and Computational Linguistics
Department of Philosophy, Linguistics and Theory of Science
University of Gothenburg
Box 200, SE-405 30 Gothenburg, Sweden
Phone: +46317864962
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