[CWB] cqpserver: Number of connections

[Stefan Evert]

> On 22 Oct 2020, at 11:45, Jörg Knappen <j.knappen at mx.uni-saarland.de> wrote:
> 
> I have installed the recent cqpserver and I have six clients (SRUCQiBridge) that want to make connections to the server. The first five work just fine, but the sixth fails to connect. Also, the Perl client (CWB-CQI) fails to connect to the cqpserver in this situation.
> 
> So is there a limit of 5 connections to the cqpserver? Can I enlarge this limit?

Not intentionally, and I can't see anything in the code that would keep cqpserver from accepting further connections. I googled a bit and all the Stackoverflow answers and tutorials I could find indicate that the networking code in cqpserver is correct.

However, I just noticed that we configure the listen() call to allow for a backlog of up to 5 pending connections.  So if they somehow don't get cleared out when the server accepts a connection and forks, that would explain your observation.   I cannot reproduce the behaviour on my MacBook with CQPserver v3.4.26 and CWB::CQI clients (MicroCQP.perl from the Perl package examples).

We'll need more information in order to help you diagnose the problem:

 - What platform and OS version are you running?

 - Are CQPserver and client running on the same machine or across a network connection?

 - Any special setup, sandbox, etc. for the CQPserver?

 - Can you reproduce the problem using only "cqpserver" and the "CWB::CQI::Client" package?  A reproducible example would certainly help us get a handle on this.

 - Please run cqpserver with -d ServerLog -d ServerDebug and post the console output; perhaps it allows us to see at what point cqpserver gets stuck.  You could also try adding -d Snoop, though I don't think it'll give use additional useful information.

Best,
Stefan