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,

I have noticed that all our replies are missing from the conversation. Do you see the same on your end?

Can you please specify all required steps for replicating your issue on the nrf9151-dk?
Please also include information about NCS version and modem firmware version.

Best regards,
Dejan

[Deval]

I can see all the replies but they are nested within the other replies. 

Serial LTE Modem example with NCS version is 3.1.0, with the overlay-ppp-cmux-linux added. 

You must use a Hologram SIM and the UDP messaging feature on the specific port -- we are using port 6002. 

I have the UDP server and messaging working BUT only when I close the PPP explicitly. I am wondering WHY I need to close PPP in order to use the UDP server?

Is there a way to use the second PDN context for the UDP server?

[dejans]

Hi,

I have discussed your problem with our developers. Below you can find some points to consider.
To get both PPP and UDP connection to work, you need to have 2 working PDN connections. If I remember correctly (because I cannot see your previous replies) there was no IP address in your second PDN context. In this case, it seems that either your PDN context does not work or you have not activated it using AT+CGACT=1,1. In addition, two 2 different PDN connections might not be supported by the operator. You could check with your operator if they support 2 different PDN connections.
If #XUDPSRV cannot be bound to a non-primary PDN connection (as it is the case in older SLM versions), it is possible to create a socket, bind it to the port 6002 and poll/recv the data. 

You can also consider moving over to Serial Modem. You can read more about it in Serial Modem documentation and application description. This is recommended way going forward for getting better maintained base for your product. UDPSRV has been removed in Serial Modem Add-On in favor of using sockets and binding them.

Best regards,
Dejan

[Deval]

In the Serial Modem are we able to use CMUX and PPP at the same time?

My application requires AT commands at the same time as running a PPP connection. 

[dejans]

Hi, 

"PPP can be used in conjunction with CMUX in order to use a single UART for both AT data and PPP. When CMUX is also enabled, PPP is usable only through a CMUX channel."
You can read more in CMUX AT commands, PPP AT commands and configuration options documentation.

Best regards,
Dejan