UDP server NRF9151 using Hologram

[Deval]

Hello,

I am using the example on the Nordic DK to get UDP messages from the Hologram API to the Nordic Modem. 

AT#XUDPSVR=1,6002
#XUDPSVR: 3,"started"

OK

I very inconsistently get messages (if ever). 

I am not changing any of the standard operation of the modem. I am running the AT Command with CMUX and PPPd overlay. I am successfully able to connect to the network and run a pppd connnection, but when I start the UDP server I never get messages.

Is there some additional configuration required? 

I am following this guide: https://docs.nordicsemi.com/bundle/ncs-2.6.0/page/nrf/applications/serial_lte_modem/doc/slm_testing.html#generic_at_commands

Specifically this part "Test the UDP server with UDP proxy service:"

I know this service works on Hologram because we use it with a different modem. 

I know I have a connection to the network because this is my output from CEREG

+CEREG: 3,5,"8309","04C8B910",7

I know my APN is set correctly

AT+CGDCONT?
+CGDCONT: 0,"IP","hologram","10.90.66.67",0,0

So what is going wrong? Do I need to anything additional? I am not changing any power states. I have seen inconsistent results with SMS as well (and TCP has never worked). 

[dejans]

Hi,

Have you tried to test UDP connection using python script as shown in UDP server (points 1 and 2)?

Best regards,
Dejan

[Deval]

So I don't have a public IP address so I cannot use the python script. But I know the service that Hologram provides will let you send a UDP message to their SIMs since it uses their internal API and I see confirmation that the message was sent. 

And I have seen it work with this cell modem with the Hologram SIM it is just very inconsistent. 

For example when it worked:

#XUDPDATA: 24,"10.254.0.75",15694
how long does this take?
#XUDPDATA: 9,"10.254.0.75",20100
try again

I can see that I have a private IP

AT+CGDCONT?
+CGDCONT: 0,"IP","hologram","10.90.66.67",0,0

OK

So I know the service does work. 

Additionally, I am seeing low (or undefined signal quality), but a successful PPP connection. Is it possible causing the issue? Because I am seeing inconsistent results from SMS as well.

AT+CSQ
+CSQ: 99,99

OK
AT+CESQ
+CESQ: 99,99,255,255,255,255

OK

[Deval]

Turning off the XPPP does not work. 

I can add a second PDN context but still don't get the UDP messages. Is there a way to get the PDN context to be set for the UDP server and then other PDN context for the PPP?

AT+CGDCONT?
+CGDCONT: 0,"IP","hologram","10.90.66.67",0,0
+CGDCONT: 1,"IP","hologram","",0,0

I am using the Serial LTE Modem example. 

NCS version is 3.1.0

Is there another sample project I could use that would give me better success?

[Jimy]

 Jennifer Gibbs Here is where we are having issues.

[dejans]

Hi,

Can you verify that you have built serial LTE modem sample without PPP overlay?

Best regards,
Dejan

[Deval]

I have tried with the SLM sample without PPP and CMUX and still don't see it work. 

Can you provide an exact sample project configuration I can follow to get the UDP server working with Hologram messaging working? 

[Deval]

Okay I think I am able to make it work BUT only when I turn the PPP connection off with AT#XPPP=0

Why is this the case?

Is there a patch you can give me that will make it work when the PPP connection is running as well?

My application requires BOTH ppp and the UDP messages

[Deval]

Another idea is can I create two PDN contexts? I want them to both be the same but how would I go about creating two contexts and setting PPP to one of them and the UDP server to the other?

I created two PDN contexts but it didn't do anything...