HL7800 UDP client problem

Hello everybody…

We are facing a problem with a UDP client connection with a time server to retrieve time information using modem HL7800. GPRS connection is established, UDP connection is established but although we send the outgoing data packet to the time server no response ever arrives. You can see from the communication log that everything goes as expected until we transmit the UDP packet to the server with command AT+KUDPSND but then no +KUDP_DATA or +KUDP_RCV unsolicited indication arrives to inform that incoming data exist and since no data exist command AT+KUDPRCV returns nothing.
The whole sequence has been checked (as well as the outgoing packet) with another unit having HL6528RD modem and it works as expected.
Commununication log follows… Any help is appreciated…

AT+KPATTERN="*"


OK

AT+KCNXCFG=1,"GPRS","ep.inetd.gdsp","",""


OK

AT+KUDPCFG=1,0


+KUDPCFG: 1



OK



+KCNX_IND: 1,1,0



+KUDP_IND: 1,1

AT+KUDPSND=1,"pool.ntp.org",123,48


CONNECT

e                                               *

OK

AT+KUDPRCV=1,48


CONNECT

*

OK

AT+KUDPCLOSE=1


OK



+KCNX_IND: 1,5,30



+KCNX_IND: 1,3

Hi @pratos,
I tried doing your scenario on our module and I get same issue. But I am successful in sending data to our server. I am afraid there is a problem with the connection to the server. Can you please check the server try on another one and share observation?
Pass case:

at+kpattern="*"

OK
at+kudpcfg=1,0

+KUDPCFG: 2

OK

+KUDP_IND: 2,1
at+kudpsnd=2,“X.”,5043,48

CONNECT

OK

+KUDP_DATA: 2,521

at+kudprcv=2,521

CONNECT
*
OK

+KUDP_RCV: “X”,5043

Fail case

at+kcnxcfg=1,“gprs”,“internet”

OK
at+kudpcfg=1,0

+KUDPCFG: 1

OK

+KUDP_IND: 1,1
at+kudpsnd=1,“pool.ntp.org”,123,48

CONNECT

OK

at+kudpclose=1

Hi Vianney

Thank you very much for your interest and your suggestions.
I tried other time servers too, although as I mentioned above I have already tried retrieving time from this time server (pool.ntp.org) with another unit which has an HL6528RD modem and it works just fine… So the time server should not be an issue I suppose…
Nevertheless, I also tried time.windows.com and time.google.com which also work fine with HL6528RD but neither works with HL7800. I actually keep getting a lot of +CME ERROR: 60 errors (Internal system failure) after command AT+KUDPSND. Only one time was I able to get a “CONNECT” response after that command but when I sent the outgoing packet I got an error
+KCNX_IND: 1,0,0
+KUDP_NOTIF: 1,0

I will make a custom UDP server to perform some tests and realize if the issue is on the outgoing or the incoming packet and get back.

Thanks again…

Hi @pratos,
I have a new update for you. As my previous comment, I failed to send/receive UDP to pool.ntp.org when using an internal SIM for testing. The network might limit some outbound packages. I tried to using an external SIM and it works fine as below. Are you using external or internal SIM. Please consider using external to retest

at+cgdcont=1,“ip”,“v-internet”

OK
at+kcnxcfg=1,“gprs”,“v-internet”

OK
at+kudpcfg=1,0

+KUDPCFG: 1

OK

+KCNX_IND: 1,1,0

+KUDP_IND: 1,1
at+kudpsnd=1,“pool.ntp.org”,123,48

CONNECT

OK

+KUDP_NOTIF: 1,8
at+kpattern="*"

OK
at+kudpsnd=1,“pool.ntp.org”,123,48

CONNECT

OK

+KUDP_DATA: 1,48
at+kudprcv=1,48

CONNECT
*
OK

+KUDP_RCV: “103.97.125.133”,123

Let feel free to share any concerns you have. Help us tick Solution if your question is answered
Thanks

1 Like

Hello we found the issue.
The developer network of Vodafone requires a white list of server IPs and they allow only 3 addresses of fixed IPs.
A time server cannot be whitelisted because it might reply from a number of instances.

You sent to ntp.pool.org and the reply might come from ntp1, ntp2, etc.

Vodafone says on the production network these issues are resolved.

We will try to get access to the production network to see what goes on there.

To our surprise the AT+CCLK command brings back the network time.