receive UDP on nRF9160-dk SLM application

[AndMar8]

Hi,

I want to receive UPD message on my nRF9160-DK.

I can send UDP messages from my Nordic device to a server and from that messages I get the public IP address of my module. But when I try to receive messages, I don't receive anything.  

I use the serial LTE modem application.

I see the following links to send messages:

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/applications/serial_lte_modem/doc/TCPIP_AT_commands.html#udp-receive-data-xrecvfrom

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/applications/serial_lte_modem/doc/slm_description.html

First try:

AT#XSOCKET=1,2,0

#XSOCKET: 1, 2, 0, 17

OK

AT#XSENDTO="x.x.x.x",20080,1,"Test UDP"

#XSENDTO: 8

OK

AT#XSOCKET=0

#XSOCKET: 0, closed

OK

AT#XSOCKET=1,2,1

#XSOCKET: 1, 2, 1, 17

OK

AT#XBIND=3442

OK

AT#XRECVFROM

and after this I get: "Error: 'AT#XRECVFROM' timed out"  and I cannot send AT command to LTE Link Monitor.

-------------------------------------------------------------------------

Second try:

AT#XSOCKET=1,2,0

#XSOCKET: 1, 2, 0, 17

OK

AT#XSENDTO="x.x.x.x",20080,1,"Test UDP"

#XSENDTO: 8

OK

AT#XSOCKET=0

#XSOCKET: 0, closed

OK

AT#XSOCKET=1,2,1

#XSOCKET: 1, 2, 1, 17

OK

AT#UDPRECVFROM="x.x.x.x",3442

+CME: 0

Here I don't know how to solve this error.


-------------------------------------------------------------------------

Third try:

I set the UDP proxy to use the command AT#XUDPSVR;
So in "Configure nRF Connect SDK Project" I select "Stateful connection-oriented UDP client/server <SLM_UDP_PROXY>"

AT#XUDPCLI=1,"x.x.x.x",20080

#XUDPCLI: 1 connected

OK

%CESQ: 32,1,19,2

%CESQ: 29,1,24,3

AT#XUDPSEND=1,"Test UDP"

#XUDPSEND: 8

OK

AT#XUDPCLI=0

#XUDPCLI: disconnected

OK

AT#XUDPSVR=1,3442 or AT#XUDPSVR=2,3442

#XUDPSVR: 1 started

OK

Here it seems to work but I don't receive anything and retrying I get sometimes: "Error: 'AT#XUDPSVR=1,3442 ' timed out"

I try using the IP that I get in the receiving messages and also with the IP that I get with the command "AT+CGDCONT?"

I try also using the example script "client_udp.py" but nothing.

I try many times with all possible combinations.

What can I do? The nRF9160-DK receives messages but doesn't print them on the LTE Link Monitor or I'm using wrong AT command? Is there an error in the client code? Is the IP that I use the error? Is it possible that my server doesn't know how to reach my APN even if I specify the correct public IP address?

Please, help me to receive a simple "hello".
Thank you in advance.

Best regards

[Didrik Rokhaug]

Hi,

You should not close the socket after sending data, for so to open a new socket that you listen on.

Instead, you should listen on the same socket that you sent data from.

Also, be aware that due to Christmas vacations, response times might be slower than normal.

Best regards,

Didrik

[AndMar8]

Hi,
Thanks for the answer.
I tried without closing the socket but the recvfrom returns always this error: "Error: 'AT#XRECVFROM ' timed out" and always from here I can't send AT command through the LTE Link Monitor.
In the following I put the command used:

First try:

AT#XSOCKET=1,2,1
#XSOCKET: 1, 2, 1, 17
OK

AT#XBIND=3442
OK

AT#XSENDTO="x.x.x.x",20080,1,"Test UDP"
#XSENDTO: 8
OK

AT#XRECVFROM (here stops)

-----------------------------------------------------------

Second try:

AT#XSOCKET=1,2,0
#XSOCKET: 1, 2, 0, 17
OK

AT#XSENDTO="x.x.x.x",20080,1,"Test UDP"
#XSENDTO: 8
OK

AT#XRECVFROM (here stops)

I have to change something in the project file?

I closed socket in previous tries because I thought that I have to set the socket in client mode (AT#XSOCKET=1,2,0) to send messages and in server mode (AT#XSOCKET=1,2,1) to receive messages.

Best regards

 

[Didrik Rokhaug]

It looks like the documentation for the #XRECVFROM command has not been updated together with the code.

Could you try "AT#XRECV" (this should let you receive data from any source) or "AT#XRECVFROM=<url>,<port>" instead?

We are also working on fixing the documentation to avoid more confusion in the future.

You can track the progress here: https://github.com/nrfconnect/sdk-nrf/pull/3596

[AndMar8]

Hi,

Thanks for the answer and Good New Year!

I redownload the code from "Open nRF Connect SDK Project..." cleaning build directory.

I have just tried and the outputs are:

-First try:

AT#XRECV

ERROR

[00:05:20.988,220] ESC  [1;31m<err> tcpip: Not connected yet ESC  [0m

(I think) It is used for a TCP message (so it needs a TCP "connection") instead of a UDP message.

-Second try:

AT#XRECVFROM="x.x.x.x",20080

ERROR

It returns me an error but it doesn't block the code as before tries (it seems a good thing).

-Third try:

AT#UDPRECVFROM="x.x.x.x",20080

+CME: 0

In this case the code stops working and I have to press the button RESET to restart. I see this command (AT#UDPRECVFROM) in the link you shared.

Do I have to add something more or something different in command "AT#XRECVFROM="x.x.x.x",20080" that seems the best result for UDP message?

Best regards

[Didrik Rokhaug]

AndMar8 said:

AT#UDPRECVFROM="x.x.x.x",20080

 This command does not exist anymore, so that not working is expected.

 

AndMar8 said:

AT#XRECVFROM="x.x.x.x",20080

 Based on the discussion in the PR to fix the documentation, it seems I was wrong in my guess for what form of the command was right. So with that knowledge, this is also expected not to work.

Instead, the correct syntax for the command is the one in the documentation, and which you were originally using:

#XRECVFROM[=<size>]

What server do you send data to, and expect data in return from?

Are you certain that it does send a reply?

Can you take a modem trace?

That will let us see if the modem receives the response, and it is the application that is the problem, or if the response never arrives at the device.

[AndMar8]

Hi,

I'm sending data using NODE-RED udp-out block. I tested it with different devices and it works.
Regarding the modem trace I'm working on it.

I tried this AT command but I get an error:

first try:

AT#XRECVFROM=[4]
ERROR
[00:02:19.316,406] ESC [1;31M<err> tcpip: F

[1;31m<err> tcpip: Failed to parse AT command -11

[0m

second try:

AT#XRECVFROM

Here the code stops and it returns me an error in the window of log output under the terminal.

I'm wondering what is the correct procedure to send and receive data using UDP.

Are these steps right?
1)Opening a Socket
2) Sending data
3)Waiting for a response

Is the UDP data sent from the server buffered somehow or do I need to put the modem into receveing mode before sending the UDP data?

Best regards

[Didrik Rokhaug]

AndMar8 said:

I'm sending data using NODE-RED udp-out block. I tested it with different devices and it works.

 Were do you host it? Did you test with devices outside the local (to the server) network?

 

AndMar8 said:

AT#XRECVFROM=[4]

 The "[ ]" in the syntax means that it is an optional parameter. You should either use AT#XRECVFROM, or AT#XRECVFROM=<size>, where <size> is the number of bytes you expect to receive. You should not use "[ ]" in the command.

 

AndMar8 said:

Are these steps right?

 Yes. Assuming the device is already connected to the network.

These commands worked for me:

at#xsocket=1,2,0
#XSOCKET: 1, 2, 0, 17
OK
at#xsendto="x.x.x.x",7,1,"test"
#XSENDTO: 4
OK
at#xrecvfrom
test
#XRECVFROM: 1, 4
OK

[AndMar8]

Hi,

Thanks for the answer.

Yes I tested it with a device outside our local network and the udp packet is correctly received.

I have tried to replcate your steps but at#xrecvfrom command is not recognized and after that the modem stops answer me and i have to reboot the board.

To be clear as much as possible, these are the steps that I do:

1. at+cfun=1
2. at+cfun?
3. after that command start automatic command due to the "automatic requests"
4. after this command:
   at+cgact?
   +cgact: 0,1
   ok
   I send the AT commands that you use
5. at#xsocket=1,2,0
   #XSOCKET: 1, 2, 0, 17
   OK
6. at#xsendto="x.x.x.x",20080,1,"test"
   #XSENDTO: 4
   OK
7. at#xrecvfrom

Here the code stops working and under the terminal in the Log window immediately appears:

09:47:24.974       Error: 'at#xrecvfrom' timed out

From here all AT commands (also a simple AT) returns me this same error (Error: 'at' timed out).

Which's your modem version? What about the firmware? Are you using the slm application?

Thank you very much for the help.
Best regards