Sending UDP using the Serial LTE Modem application - AT sequence

[Bard]

Hi

I have upgraded from an early version of SLM to the latest version in nRF Connect SDK ver. 1.3.1

the SLM application is running on a custom board with a nRF52840. Using the old version of SLM, the following commands resulted in successful communication:

  

at#xsocket=1,2
at#xudpsendto="xx.xxx.xx.xxx",xxxx,"testing"
at#xudprecvfrom="xx.xxx.xx.xxx",xxxx,100,1
at#xsocket=0

What is the correct sequence of AT commands in the new version? And is there some documentation on available commands in the SLM application?

[Martin Lesund]

Hi Bard,

There is now a draft pull request for the SLM documentation up.

This version will be reviewed and most likely some changes will be added before its merged with NCS master.

[Bard]

Using the draft documentation, I ended up with this sequence:

at#xsocket=1,2,0    // must have the last zero
at#xsendto="xx.xxx.xx.xxx",xxxx,"Test UDP"

// both below works ok
at#xrecvfrom="xx.xxx.xx.xxx",xxxx
at#xrecvfrom="xx.xxx.xx.xxx",xxxx,100,1

at#xsocket=0

But at#xrecvfrom hangs if there is no data from the network. Is there a way to test before fetch, or a timeout parameter?

[Martin Lesund]

Please enable UDP proxy:

CONFIG_SLM_UDP_PROXY=y

and connect using:

• AT#XUDPCLI=<op>[,<url>,<port>[,<sec_tag>]

• AT#XUDPSEND=<datatype>,<data>

recv is handled automatically when using proxy.

"Proxy" not related to a proxy server as commonly known.
It is named a proxy as it stands between the TCP interface of the modem and the application itself.
The modem TCP/UDP layer supports full-duplex but the AT commands are blocking, 
so we need this added interface to remove the blocking behavior.

[Bard]

The following sequence now works fine:

at#xudpcli=1,"xx.xxx.xx.xxx",xxxx
at#xudpsend=1,"testdata"
at#xudpcli=0

Thank you