No packets in Wireshark

[Helmet]

Hello all!

I am running the maint-3.10 branch from bkerle's repository. I had to use that instead of  maint-3.10_with_multiarfcn since it wasn't accepting the --args parameters for some reason.

I am running this command:
grgsm_livemon --args="uhd,subdev=A:B,antenna=RX2" -f 1833.0M -g 60

I have tried with several different frequencies, both on the 900 band and the 1800 band and the reception looks good with at least 15dB SNR.

I get decoding in the terminal:
 25 06 21 00 05 f4 fe c1 b9 da 23 4c 0b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
 25 06 21 20 05 f4 20 ea 9f 2a 2b 4c 0b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
 15 06 21 00 01 f0 2b 4c 0b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
 4d 06 24 a0 1d fc d1 ec 59 f5 05 d2 5b f5 4d c6 29 f7 92 70 d3 00 0b
 25 06 21 20 05 f4 3c fa f6 31 2b 4c 0b 2b 2b 2b 2b 2b 2b 2b 2b 2b 2b
 41 06 21 20 05 f4 25 e5 da c8 17 05 f4 ca c5 02 62 2f 4c 0b 2b 2b 2b
 

But I get no packets in Wireshark when running this:
sudo wireshark -k -f udp -Y gsmtap -i lo

I have played around with the ppm quite a bit but it makes no difference. Have tested within a range of -100 to 100 with no success. I got the frequencies from running grgsm_scanner.

I get the normal UDP packages in Wireshark but nothing when filtering for gsmtap packages. The stream of data is constant in the terminal.

• Ubuntu 22.04, fairly fresh install
• GNU Radio 3.10.1.11

Any ideas?

[Helmet]

If anyone comes across this same problem they might want to know that the default port for gsmtap packets in Wireshark is 4729 and the default in the version of gr-gsm that I listed previously is 4730 so I had to use this command instead to make it work:

grgsm_livemon --args="uhd,subdev=A:B,antenna=RX2" -f 1833.0M -g 60 --collectorport 4729

Best of luck!