receive UDP on nRF9160-dk SLM application

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Thu, 04 Mar 2021 14:05:35 GMT

[quote user="AndMar8"]If I send the AT command AT#XRECVFROM to my module, is there a AT command that allows to exit from RX mode without press the button reset?[/quote]

No.

But, you can use the proxy service: https://devzone.nordicsemi.com/f/nordic-q-a/66288/sending-udp-using-the-serial-lte-modem-application---at-sequence/272293#272293

That will keep the SLM from locking up.

See scanrio 3 here: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/applications/serial_lte_modem/doc/slm_testing.html#udp-client

https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/applications/serial_lte_modem/doc/TCPIP_AT_commands.html#udp-dtls-client-xudpcli

RE: receive UDP on nRF9160-dk SLM application

Achim Kraus — Thu, 04 Mar 2021 08:17:31 GMT

> Firstly I used a random port to send the reply from my Node-Red.

That would have worked, if no NATs would be on the route. But with NATs, such traffic is blocked. The mapping contains the port as well and so from the view of the NAT there is no route back to the modem.

> Or the only way is to change the timer in the code to stop the receive mode?

That's at least what I do, and what is done in common. Therefore the setsockopt/SO_RCVTIMEO is for. Though I patched the SLM for that, I'm not sure, how to do that with AT#XSOCKETOPT/SO_RCVTIMEO.

RE: receive UDP on nRF9160-dk SLM application

AndMar8 — Thu, 04 Mar 2021 07:56:20 GMT

Hi Didrik!

It works with my application (Node-Red). It was my trivial error.
From your pcap file I understand that I have to bind the communication to the port used by the application to receive, in order to send a reply to nRF9160-dk. I thought that (with the udp protocol) it didn't matter to specify the port from which the message came out but only the destination one.

My mistake was the following:
nRF9160-dk sends from random port, for example 59222, to my Node-Red port 20080 a message.
Reply
Node-Red has to send a reply from the same port 20080 to the port (in this case) 59222.

Firstly I used a random port to send the reply from my Node-Red.

Thank you so much for your time and your suggestion.

I have one last question.

If I send the AT command AT#XRECVFROM to my module, is there a AT command that allows to exit from RX mode without press the button reset? Or the only way is to change the timer in the code to stop the receive mode?

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Tue, 02 Mar 2021 10:32:20 GMT

[quote user="AndMar8"]What kind of application do you use to send udp messages to nRF9160-dk?[/quote]

It's a Rust application I have written myself, although at this point it is still mostly just one of the examples from the documentation. Below is a simplified version (fostly just fancy logging that is removed):

fn single_udp_echo() -> std::io::Result<()> {
    let socket = std::net::UdpSocket::bind("0.0.0.0:56227")?;

    println!("Listening on socket 56227");

    let mut buf = [0; 1024];
    
    let (amt, src) = socket.recv_from(&mut buf)?;
    println!("Received message from {:?}", src);
    
    let buf = &buf[..amt];
    debug!("{}", std::str::from_utf8(&buf).unwrap());
    
    socket.send_to(buf, &src)?;

    Ok(())
}

fn main() {
    println!("Starting UDP echo");
    
    loop {
        let udp_result = udp::single_udp_echo();
        println!("udp result: {:?}", udp_result);
    }
}

It is simply listening for a UDP message, printing it, and sending it back to the sender.

Log from the server (including my own test to check that the server was up and running), timestamps are in UTC:

[2021-03-01T13:31:10.504010113][INFO][server] Starting UDP echo
[2021-03-01T13:31:10.504231159][INFO][server::udp] Listening on socket 56227
[2021-03-01T13:32:10.600723109][DEBUG][server::udp] Received message from 62.93.143.64:44856
[2021-03-01T13:32:10.601072018][DEBUG][server::udp] didrik port test
[2021-03-01T13:32:10.601381792][WARN][server] udp result: Ok(())
[2021-03-01T13:32:10.601632681][INFO][server::udp] Listening on socket 56227
[2021-03-01T16:34:44.897245414][DEBUG][server::udp] Received message from 151.99.1.113:59409
[2021-03-01T16:34:44.897544864][DEBUG][server::udp] Hi, I'm AndMar8
[2021-03-01T16:34:44.897827920][WARN][server] udp result: Ok(())

And .pcap:

devzone.nordicsemi.com/.../udp.pcap

It is also worth noting that the log and .pcap shows NATing both in my and iBasis' networks.

The IP address the server logs is not the same address as reported by my nRF9160, and the server's address in the .pcap is also a local address and not the one used by the devices.

[quote user="AndMar8"]It doesn't block the code as I thought but it's still worked.[/quote]

Correct. That error is reported by the Link Monitor, which has a rather short timeout for AT command responses. The error message can be useful for most AT commands, as they reply immediately. However, for commands which might take some time (such as waiting for a reply from a server), the timeout can be ignored.

In conclusion, it seems the problem is with the NODE-RED server (or the server hits a limitation in the network). How fast does it reply to the UDP packets?

We have often seen NAT timeouts of ~ 1 minute, but we have also seen networks where they are significantly shorter.

RE: receive UDP on nRF9160-dk SLM application

AndMar8 — Mon, 01 Mar 2021 16:42:43 GMT

Hi,

I have just tried and it works. I receive my same message.

The output file is shared.

So the AT command works but I don't know why my NODE-RED for udp doesn't work. Could you see the IP address that is used by your server to reply to my message?

devzone.nordicsemi.com/.../udp.txt

RE: receive UDP on nRF9160-dk SLM application

AndMar8 — Mon, 01 Mar 2021 14:02:52 GMT

Hi,

Unluckily I had already tried with the IP that I got with AT+CGDCONT? and I have the same results.

Just to let you know, I had done other test with different types of protocol of communication:

MQTT works fine: I connect the nRF9160 to a topic of a block of NODE-RED and i can receive and send messages.

TCP works fine only if I use the nRF9160 as client which has to connect to NODE-RED (as server). In this case I can send and receive message.
But if I use NODE-RED as client which has to connect to nRF9160 (as server), when I use the commands AT#XLISTEN and AT#XACCEPT, nothing happens.
I try both with the IP address of the screenshot (151.x.x.x) and with the IP address that I get with the command AT+CGDCONT? (10.x.x.x).

I think it could be for the same reason of UDP RECVFROM.

However I think that the correct IP address is 151.x.x.x and not 10.x.x.x.

I found out also that in the LTE Link monitor if I got in the Log window:

Error: 'at#xrecvfrom' timed out

It doesn't block the code as I thought but it's still worked. I got the same error with TCP protocol and AT#XRECV but I can receive messages, too. So fine :).

What kind of application do you use to send udp messages to nRF9160-dk? So I'll try with it, instead of NODE-RED. Probably has problem with UDP protocol.

Now I try the commands you send me! Thank you very much! 🙂

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Mon, 01 Mar 2021 13:49:59 GMT

Hi AndMar8,

Could you try the following sequence of commands (with the same server and port)?

AT+CEREG=5
AT+CSCON=1
AT+CFUN=1
// Wait for the nRF9160 to be connected (CEREG 1 or 5)
AT#XSOCKET=1,2,0
AT#XSENDTO="84.215.43.232",56227,1,"<some text here>"
AT#XRECVFROM

You should then end up with a log similar to this (if you have enabled debug logging):

devzone.nordicsemi.com/.../slm_5F00_udp_5F00_working.txt

As you can see from the log, I have verified that this server works, and I am able to communicate with it with my nRF9160DK and iBasis SIM card.

I also have some logging running on the server, so it I can confirm that it receives the packet and sends a response.

And, as always, if you could share the log and modem trace afterwards, that would be great.

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Thu, 25 Feb 2021 14:34:39 GMT

[quote user="AndMar8"]I didn't find CONFIG_SLM_LOG_LEVEL=y so I guess you mean CONFIG_SLM_LOG_LEVEL_DBG=y (I hope it's correct).[/quote]

Yes, sorry. That was a typo on my part.

I also forgot to mention that you have to comment out the CONFIG_SLM_LOG_LEVEL_INF=y line (or replace it with *_DBG=y).

I have also done some more tests myself, and it doesn't seem like the recvfrom call actually gets registered in the modem trace unless it returns some data.

So the 2nd point in my last comment doesn't seem to be an actual problem, just another indication that the device never receives the response.

[quote user="AndMar8"]is there an at command to get the IP address of my nRF9160?[/quote]

AT+CGDCONT?

But, it is worth noting what Achim Kraus says about NAT.

RE: receive UDP on nRF9160-dk SLM application

Achim Kraus — Fri, 19 Feb 2021 16:50:16 GMT

Usually, neither the local ip-address your nRF9160 nor the local port you use will be visible at the server. The mobile provider mostly use a NAT, which exchanges that address and port. And because of that NAT, you must respond "in time". I would try to start with less than 30s.

RE: receive UDP on nRF9160-dk SLM application

AndMar8 — Fri, 19 Feb 2021 16:44:01 GMT

Hi,

1. I believe that the messages are sent by my device because when I send messages from nRF9160 they appear on the node-red debug messages window (as in the screeshot). However to be sure is there an at command to get the IP address of my nRF9160?

2. Debug:

I didn't find CONFIG_SLM_LOG_LEVEL=y so I guess you mean CONFIG_SLM_LOG_LEVEL_DBG=y (I hope it's correct).

For the debugging I also set in the prj.config file:

CONFIG_USE_SEGGER_RTT=n
CONFIG_RTT_CONSOLE=n
CONFIG_UART_CONSOLE=y
CONFIG_LOG_BACKEND_RTT=n
CONFIG_LOG_BACKEND_UART=y

I attached the zip with modem trace bin, terminal of Termite, logfile of LTE Link Monitor and the prj.config file

devzone.nordicsemi.com/.../nRF9160-log.rar

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Fri, 19 Feb 2021 13:20:45 GMT

Hi,

I've had a quick look at your traces so far, and I have noticed two things:

1. Neither the IP address or the source port (from the device) matches your screenshot from the server. Are you sure the screenshot is from the nRF9160?

2. The modem never receives an recvfrom RPC call from the application core.

To debug 2 further, could you enable debug logging in the SLM (by setting CONFIG_SLM_LOG_LEVEL=y), and capture the debug log which will be sent over RTT (as well as the UART log and a modem trace)?

But, the device never receives the reply from the server, so even if the recvfrom call had been there, you still wouldn't have seen any response.

RE: receive UDP on nRF9160-dk SLM application

AndMar8 — Thu, 18 Feb 2021 11:09:41 GMT

Hi, Sorry for the delay. I were able to collected the modem Trace.
Please find attached the zip file containing two modem traces.

I have also tested the receive mode using a different terminal. I use Termite as both putty and were not able to communicate with the SIP:

Just for knowledge I have tested the sim card with a different modem from Quectel and I was able to receive the data coming from the node-red UDP node.

I have also tested the UDP functionality with a desktop packet receiver and it works as well.

Here a screen shot from node-red showing the message I am receiving from the SIP. OFC I use the same address and port to send data back to the SIP.

I am starting being clueless about why I am not able to receive the UDP packet using the nrf9160 SIP.

I do not know if it can be useful but, can you please share your firmware HEX files just to test it.

Thank you for your kind help.

devzone.nordicsemi.com/.../nRF9160_5F00_recvfrom_5F00_trace.zip

RE: receive UDP on nRF9160-dk SLM application

Achim Kraus — Mon, 18 Jan 2021 20:42:29 GMT

> 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.

How long does it take until you send the message back?

If you get the public IP address from the message, do you also get the source port from them? And do you use that port to send a message back?

RE: receive UDP on nRF9160-dk SLM application

Achim Kraus — Mon, 18 Jan 2021 20:34:39 GMT

> The SLM implementation of #RECVFROM is blocking, so this is not surprising.

Sorry to write that, surprising is indeed not the behavior, it's more, that it is implemented in that way. Doesn't this block the modem for new AT-commands until it receives something? If the sent data is lost, you will not be able to even resend it. For me this implementation is very close to "useless"?

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Fri, 15 Jan 2021 11:49:46 GMT

[quote user="AndMar8"]
Which's your modem version? What about the firmware? Are you using the slm application?[/quote]

mfw v1.2.2, SLM from NCS v1.4.0.

[quote user="AndMar8"]
09:47:24.974 Error: 'at#xrecvfrom' timed out[/quote]

I assume you are using the LTE link monitor?

It is note really meant for this kind of use case, but to communicate with the modem "directly". As such, almost all the AT commands it is "meant" to send returns a reply immediately. It therefore has a fairly short timeout. However, it should not be a problem that a command times out, as long as there is a response eventually.

[quote user="AndMar8"]From here all AT commands (also a simple AT) returns me this same error (Error: 'at' timed out).[/quote]

The SLM implementation of #RECVFROM is blocking, so this is not surprising.

Can you take a modem trace, so we can analyze the IP traffic?

Also, if you could capture an IP trace from your server, that could also help.

RE: receive UDP on nRF9160-dk SLM application

OlivierG34 — Thu, 14 Jan 2021 14:49:41 GMT

Hi,

Correct me if im wrong but are you sure the IP given by the LTE network is a PUBLIC IP ? Except specifically asked when you order the simcard, the IP are "private IP" on the operator's network...
OlivierG

RE: receive UDP on nRF9160-dk SLM application

Achim Kraus — Thu, 14 Jan 2021 14:19:29 GMT

Basically, I use the "serial_lte_modem" successfully , but I patched the "xrecvfrom".

That command is based on "recvfrom", which according https://linux.die.net/man/2/recvfrom uses the "src_addr" as **OUT** not **IN** parameter. The original implementation seems to assume, that this is an **IN** parameter. So, my patch applies a recv_timeout via setsockopt and then calls the recvfrom using the OUT parameter src_addr to fill the received source information also into my adapted at-response.

I'm not sure, if this is just a mistake by the developer to assume, the src_addr is **IN**, or if this is really the intention.

(As additional hint related to the last question about the PUBLIC IP:

My server returns the response just to the source-address, the server receives the package from (as usual for UDP).)

RE: receive UDP on nRF9160-dk SLM application

AndMar8 — Thu, 14 Jan 2021 11:11:22 GMT

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:

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

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Wed, 13 Jan 2021 16:14:27 GMT

[quote user="AndMar8"]I'm sending data using NODE-RED udp-out block. I tested it with different devices and it works.[/quote]

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

[quote user="AndMar8"]AT#XRECVFROM=[4][/quote]

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.

[quote user="AndMar8"]Are these steps right? [/quote]

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

RE: receive UDP on nRF9160-dk SLM application

AndMar8 — Tue, 12 Jan 2021 09:47:06 GMT

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

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Thu, 07 Jan 2021 15:47:03 GMT

[quote user="AndMar8"]AT#UDPRECVFROM="x.x.x.x",20080[/quote]

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

[quote user="AndMar8"]AT#XRECVFROM="x.x.x.x",20080[/quote]

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.

RE: receive UDP on nRF9160-dk SLM application

AndMar8 — Tue, 05 Jan 2021 10:22:43 GMT

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

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Mon, 04 Jan 2021 15:52:23 GMT

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

RE: receive UDP on nRF9160-dk SLM application

AndMar8 — Tue, 22 Dec 2020 16:03:45 GMT

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

RE: receive UDP on nRF9160-dk SLM application

Didrik Rokhaug — Tue, 22 Dec 2020 14:58:31 GMT

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