On Sun, Apr 3, 2016 at 8:49 AM, Andy Walls <a...@silverblocksystems.net>
wrote:

>
> > Otherwise, you didn't drop a control port related block on the
> > flowgraph did you?
>
>
> Here is some good info on how GRNURadio's control port works at a high
> level:
> https://gnuradio.org/redmine/projects/gnuradio/wiki/ControlPort
> https://gnuradio.org/doc/doxygen/page_ctrlport.html
>
> From that second page, it appears that running two flowgraphs on the
> same machine has a problem caused by Apache Thrift and GNURadio's
> configuration of the Control Port network port (default of 9090).
> https://gnuradio.org/doc/doxygen/page_ctrlport.html#ctrlport_thrift_issues
>
> So please only run on flowgraph at a time, at first, to troubleshoot
> this issue.
>
> Second, you may want to try setting the GR_CONF_THRIFT_PORT environment
> variable to something other than 9090, a port that you know is open on
> your machine, for each separate flowgraph that you run.
>
> FYI, the modulate_vector block runs a "mini"-flowgraph, before the main
> flowgraph actually runs:
>
>
> https://github.com/gnuradio/gnuradio/blob/master/gr-digital/lib/modulate_vector.cc#L59
>
> Hopefully, there isn't some sort of weird race condition with the Thrift
> port being open for the modulate_vector block's mini-flowgraph and the
> main flowgraph.
>
>
> Hi Tom,
>
> Do you have any comments or insights on Arik's Thrift error message
> and/or the possibility of modulate_vector's mini-flowgraph causing
> problems with Thrift's network port and the main flowgraph?
>
> Regards,
> Andy
>

Andy,

I think you've got it on the Thrift issue. However, running the modulate
vector mini flowgraph first should kill itself immediately and free up the
port, so I don't think that's the problem. On the other hand, I've been
seeing issues recently where every time I launch GRC, it seems to cause a
conflict with whatever port I'm setting. Almost as though GRC is launching
something and holding on to the port specified in the thrift.conf file. I
thought this could just be a problem on my laptop (I've been traveling a
lot -- more than usual even -- and developing on my laptop can lead to me
doing a lot of crazy things), but I think I've since seen it on my office
workstation as well. That could be a problem here, too. We'll have to track
that down.

Using the GR_CONF_THRIFT_PORT variable is a good idea to set the port per
flowgraph you're running. Another option is to set the port to 0 in
thrift.conf, which will cause Thrift to open an ephemeral port for each
server is creates. You'll just have to pay attention to the message output
that announces the ControlPort endpoint to find out what port it's running
on.

Tom
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