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Re: ControlPort error in gr-ieee802-11, wifi-loopback example.

From: Anton Ottosson
Subject: Re: ControlPort error in gr-ieee802-11, wifi-loopback example.
Date: Mon, 5 Jul 2021 18:56:17 +0000

Hi Bastian,

How exciting to get an answer from the author himself! Great to hear that you updated the readme, even though I really should have figured out what was going on faster. But I suppose we all get tunnel vision sometimes, when assuming something is wrong. Even better to hear that CtrlPort is entirely optional. I did try to rebuild GR with PyBOMBS after installing Thrift, but it did not work immediately, and since I was already pretty sure it was optional I decided not to waste any more time on it.



From: Bastian Bloessl <mail@bastibl.net>
Sent: Monday, July 5, 2021 8:00:28 PM
To: Anton Ottosson; discuss-gnuradio@gnu.org
Subject: Re: ControlPort error in gr-ieee802-11, wifi-loopback example.
Dear Anton,

On 7/3/21 6:54 PM, Anton Ottosson wrote:
> I see now my silly mistake. I thought the "xxxxxxxxxx" messages printed
> in the console were due to an error with ControlPort/Thrift, but it
> turns out these were the literal messages being sent by the `Message
> Strobe`. So the combination of the readme saying I should expect "Hello
> World" and me seeing the message about ControlPort and Thrift made me
> assume there was something wrong with the messaging, without actually
> taking the time to inspect the flowgraph a little bit more carefully.

Arg, sorry for the confusion. I updated the readme and removed the
"hello world" reference. At some point, I added a slider to adjust the
frame size and changed the payload from "hello world" to "x" * frame_size.

> So it seems to be working as intended, I think, and I can disable the
> `CtrlPort Performance Monitor` block to get rid of the message about
> ControlPort/Thrift. This still leaves me wondering a couple of things
> though:

Yes, just disabling is fine.

>  1. What is the `CtrlPort Performance Monitor` block for? Is it
>     necessary for anything in `gr-ieee802-11`?

GNU Radio comes with CtrlPort, which provides an interface to a
flowgraph that allows to get and set parameters/data, for example, from
an external program.

Performance Counters can be enabled in a GNU Radio flowgraph to record
statistics about queue sizes, CPU time of blocks, and other performance

The CtrlPort Performance Monitor starts a GUI that visualizes
performance figures of a flowgraph, polling its performance counters
through the CtrlPort interface.

It is completely irrelevant for the functionality of the flowgraph. Just
disabling the block is fine.

>  2. Why does it not work, since I have Thrift installed?

I don't use PyBombs but AFAIS gnuradio-default installs gnuradio 3.8
without a dependency on thrift. Installing thrift afterwards doesn't
help since gnuradio probably doesn't get recompiled. If you want
CtrlPort, I'd recommend to reinstall gnuradio. It should detect thrift
during the build. If it still doesn't work, check the cmake output to
figure out why the component was not enabled.


> But I will look inte these things myself, so don't waste your time
> writing an answer for me, unless you really want to 😊
> Regards,
> Anton
> ------------------------------------------------------------------------
> *From:* Anton Ottosson
> *Sent:* Saturday, July 3, 2021 5:47:08 PM
> *To:* discuss-gnuradio@gnu.org
> *Subject:* ControlPort error in gr-ieee802-11, wifi-loopback example.
> Hi,
> I am trying to set up `gr-ieee802-11`
> (https://github.com/bastibl/gr-ieee802-11
> <https://github.com/bastibl/gr-ieee802-11>), `maint-3.8` branch, with
> GNU Radio 3.8. As recommended in the readme I run the
> `wifi_loopback.grc` example flowgraph, expecting to see some decoded
> "Hello World" packets in the console. The flowgraph runs, but the output
> does not show what I expected. The most important part of the output is
> probably the message
> `Failed to to connect to ControlPort. Please make sure that you have
> Thrift installed and check your firewall rules.`
> printed during startup. More details, including console output, can be
> seen
> here: https://github.com/bastibl/gr-ieee802-11/issues/292#issuecomment-873317584
> <https://github.com/bastibl/gr-ieee802-11/issues/292#issuecomment-873317584>
> I must confess that I don't really know what the role of  "ControlPort"
> and Thrift is here, so I'm not sure how to proceed. But this is not what
> the output is supposed to be, right? Has anyone here had the same
> problem, and found a way to get past it?
> My current setup was installed using PyBOMBS, under Ubuntu 20.04.2 LTS.
> To be precise i initialized a PyBOMBS prefix with
> `gr-recipes/gnuradio-default` and then installed
> `gr-recipes/gr-ieee-80211`. After seeing the message above I also
> installed `gr-recipes/apache-thrift`, hoping that this would solve the
> issue, but it did not seem to make any difference.
> Best regards,
> Anton

Dr. Bastian Bloessl
Secure Mobile Networking Lab (SEEMOO)
TU Darmstadt, Germany

GitHub/Twitter: @bastibl

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