Unable to send UDP packets via NTN connectivity

[barbiz]

Hello,

I am evalating the nRF9151-SMA-DK with a Monogoto SIM card that uses Skylo NTN connectivity.

I am able to reach the internet, since DNS resolution works:

Ready
> AT%XSYSTEMMODE=0,0,0,0,1

OK
> AT%XBANDLOCK=2,,"23,255,256"

OK
> AT%LOCATION=2,"45.40946744518183","11.910658449997351","0",0,0

OK
> AT+CGDCONT=0,"IP","go.mono"

OK
> AT+CEREG=5

OK
> AT+CNEC=24

OK
> AT+CSCON=3

OK
> AT%MDMEV=2

OK
> AT+CFUN=1

OK

%MDMEV: SEARCH STATUS 1

+CEREG: 2,"3AA3","00110383",14

%MDMEV: PRACH CE-LEVEL 0

+CSCON: 1,7,4

+CEREG: 5,"3AA3","00110383",14,,,"11100000","00111000"

%MDMEV: SEARCH STATUS 2

+CSCON: 0,7,4
> AT#XGETADDRINFO="google.com"

#XGETADDRINFO: "142.251.14.138"

OK

%MDMEV: PRACH CE-LEVEL 0

+CSCON: 1,7,4

Then I have set an UDP server, public on the internet, at address <server_ip>

I tested the reachaiblity of the server from public network with my pc as a client using a python script to send UDP packets.

However, when sending UDP packets with the nRF9151, nothing gets to the server.

> AT#XSOCKET=1,2,0

#XSOCKET: 0,2,17

OK

> AT#XSENDTO=0,0,0,"<server_ip>",9999,"test"

#XSENDTO: 0,0,4

OK

The provider confirms the SIM card is configured correctly, however I am unable to continue testing.

Can you help me?

[Syed Maysum Abbas Zaidi]

Hi,

Thanks for testing with flag 512. It means the modem believes it transmitted the packet over NTN, but does not prove it traversed the operator core or reached your server, this do suggests that there is an issue on operator side however can you please run one more check, which can tell if the send is acknowledged:

AT#XSENDTO=0,0,8192,"18.199.178.22",9999,"test"

Then wait for the #XSENDNTF. If status = -1, the modem itself reports a failure. If status = 0 but nothing arrives at the server, the issue is downstream (operator path or firewall). 

Moreover please share the Modem traces with AT#XTRACE command, so we can debug it further.

Best Regards,
Syed Maysum