How to connect

  • We are testing in Germany with an eSim from T-mobile and should be sending UDP packages to a server in Norway. Do we need to register somewhere (CDP ?) in order to forward to our server? If so, where to register? This is not necessary in Norway by Telia or Telenor, where it’s just touch and go.
    The quick start guide didn’t mention this.

  • Deutsche Telekom IoT

    Hi Inge, that is very odd. We don’t have eSIM’s for the Dutch IoT network yet…

  • Deutsche Telekom IoT

    What exactly do you mean with eSIM? Could it be a MFF SIM card (embedded SIM)?

  • Yes. eSIM - embedded SIM.

  • It is a NB-IOT M2M Basic GSIM MFF TUAK
    delivered from you.

    It is a custom sensor based on nrf9160 from Nordic Semiconductor. This chip is using sockets to set up the modem (not AT commands!). This statement opens the socket: client_fd = socket(AF_INET, SOCK_DGRAM, 0);
    This works fine in Norway with both Telia and Telenor eSIM.
    The sensor sends a UDP packet with this statement: err = send(client_fd, send_buf, sizeof(send_buf), 0); directly to our server (not via Telenor or Telia cloud).
    Is it possible to do the same in Germany?
    We don’t want to send UDP packets via your server (IP, but directly to our server in Norway. Is this possibly also in your network?

    Alternatively we have to send packets to your cloud, and then redirect the traffic to our server. If so, could you please advise how to make your cloud transparent to UDP packets from our sensors.

  • Hi Inge,

    the information provided in this thread is somewhat confusing for me, so I have to ask some questions in return to assess the problem. You state, that you are using an embedded SIM from T-Mobile NL and that you have no access to the Telekom Deutschland network in Germany, is this correct?
    Have you checked, if the card is enabled for roaming within other Natcos of DT? Not all cards are allowed to do so. Your sales contact at T-Mobile NL should be able to provide this information.
    In general we offer cards for testing with access to any given public IP in the the Internet via TCP or UDP. In any case, the addressing needs to be done with the public IP of your server, as our NB-IoT network does not resolve DNS queries.
    Could you also provide the API calls to the nrf9160 which you are using to attach to the network? In particular those for APN configuration, Attach and configuration of bands.

    Best regards,

  • Hi
    The SIM is from Telekom Deutschland. Not Holland. The Germans have given the link to this forum, so there is no connection to Holland from our side. It’s your assumption that this has something to do with Holland. It has not.

    Best regards,

  • Hi Inge,

    alright, I was just confused because of the statement “eSim from T-mobile”. Anyway, this means you have probably a card with the APN is this correct?

    With this a connection to any server in the internet should be possible, as long as you do the addressing via IP.

    Best regards,

  • Thank you Thorsten
    Yes, the APN is
    DNS works with Telia and Telenor, but we need to hardcode the IP here. Understood.

    Best regards

  • @inge-eriksen

    Yesterday we did some testing in Hamburg. The results was not very satisfying. Some questions and logs:

    • Why do we get “<reject_cause> = 15 -> No suitable cells in tracking area” when trying to connect to Deutche Telekom in Hamburg?
    • When the UE finally briefly connects to Deutche Telekom, we get “ <stat> = 5” meaning “Registered, roaming”. Why roaming and not “ <stat> = 1” home network?
    • Why does the UE try to connect to Vodefone when we have a Deutche Telekom eSim? In Norway we are using both Telia and Telenor eSims, and the UE always connects to the correct network.

    At the end of the log is a similar test done in Norway with a Telenor eSim. There is no problem in Norway. The UE connects within less than a minute, and stays connected.

    Testlog from test in Hamburg, Germany
    Lines starting with “2020” is log from server in Norway
    Lines starting with “A” is at commands logged via serial port to UE (locally)
    Lines starting with “NOTE:” is my notes to the log

    2020-02-04 12:00:39.600333 received 19 bytes from (‘’, 15829)
    2020-02-04 12:21:29.490427 received 19 bytes from (‘’, 29288)
    2020-02-04 12:31:42.604563 received 19 bytes from (‘’, 17698)
    NOTE: Received three packets to server
    NOTE: UE sends every 10 min, but we didn’t receive packet as expected at 12:10 --> reset UE after this
    NOTE: last two packets from same IP and 10 min apart --> normal operation (by chance?)

    A 14:21:53.739 “at+cereg?” sent
    A 14:21:53.743 "+CEREG: 5,4,“A755”,“00511265”,9,0,15,“11100000”,“11100000” " received
    A 14:21:53.745 "OK " received
    NOTE: Moved location from airport to downtown Hamburg -> start logging at commands
    NOTE: <stat> = 4 -> Unknown (e.g. out of E-UTRAN coverage)
    NOTE: <cause_type> = 0
    NOTE: <reject_cause> = 15 -> No suitable cells in tracking area
    NOTE: <ci> = 00511265 -> Vodafone at Große Bleichen, Neustadt, Hamburg-Mitte -> not Deutche Telekom
    NOTE: Maybe no coverage from Deutche Telekom ? -> change location

    A 15:01:18.102 “at” sent
    A 15:01:18.105 "OK " received
    A 15:01:41.892 “at+cereg?” sent
    A 15:01:41.898 "+CEREG: 5,4,“FFFE”,“FFFFFFFF”,9,0,0,“00000000”,“00000000” " received
    A 15:01:41.899 "OK " received
    A 15:02:19.138 "+CEREG: 2,“D71E”,“018C920C”,9,0,0,“11100000”,“11100000” " received
    A 15:02:21.867 "+CEREG: 5,“D71E”,“018C920C”,9,“11100000”,“00001100” " received
    A 15:02:23.037 "+CEREG: 5,“D71E”,“018C920C”,9,“00100001”,“00001100” " received
    2020-02-04 15:02:23.591557 received 19 bytes from (‘’, 23327)
    NOTE: received one successful packet at 15:02
    NOTE: <ci> = 018C920C -> Deutche Telekom at Heiligengeistbrücke, Neustadt, Hamburg-Mitte
    NOTE: <stat> = 2 and 5 -> Not registered and Registered, roaming. <- why roaming and not home network?

    A 17:02:18.300 “at” sent
    A 17:02:18.302 "OK " received
    A 17:02:40.335 “at+cereg?” sent
    A 17:02:40.337 "+CEREG: 5,4,“FFFE”,“FFFFFFFF”,9,0,0,“00000000”,“00000000” " received
    A 17:02:40.531 "OK " received
    A 17:02:44.235 "+CEREG: 2,“D70A”,“01939209”,9,0,0,“11100000”,“11100000” " received
    A 17:07:00.853 “at” sent
    A 17:07:00.857 "OK " received
    A 17:07:26.009 “at%xcband” sent
    A 17:07:26.014 "%XCBAND: 0 " received
    A 17:07:26.205 "OK " received
    A 17:07:38.297 "+CEREG: 2,“A754”,“005A9566”,9,0,0,“11100000”,“11100000” " received
    2020-02-04 17:11:21.320059 received 19 bytes from (‘’, 6961)
    2020-02-04 17:21:33.137809 received 19 bytes from (‘’, 28355)
    NOTE: Location changed -> Hamburg airport
    NOTE: two packets successfully received at 17:11 and 17:21, same IP (sadly no at log when it happens)
    NOTE: <ci> = 01939209 -> Deutche Telekom, Flughafenstraße, Fuhlsbüttel, Hamburg-Nord
    NOTE: <ci> = 005A9566 -> Vodafone, Burgunderweg, Niendorf, Eimsbüttel, Hamburg <- why didn’t the UE stay on 01939209 ?
    NOTE: <stat> = 2 -> Not registered, but UE is currently trying to attach or searching an operator to register to.

    A 17:38:36.047 “at” sent
    A 17:38:36.051 "OK " received
    A 17:39:11.148 “at+cereg?” sent
    A 17:39:11.153 "+CEREG: 5,4,“FFFE”,“FFFFFFFF”,9,0,0,“00000000”,“00000000” " received
    A 17:39:11.153 "OK " received
    A 17:39:18.755 "+CEREG: 2,“A754”,“005A9566”,9,0,0,“11100000”,“11100000” " received
    A 17:39:19.535 "+CEREG: 4,“A754”,“005A9566”,9,0,15,“11100000”,“11100000” " received
    A 17:39:19.540 "+CEREG: 4,“FFFE”,“FFFFFFFF”,9,0,15,“11100000”,“11100000” " received
    A 17:39:38.256 "+CEREG: 4,“A754”,“00607765”,9,0,15,“11100000”,“11100000” " received
    NOTE: UE is changing <ci>
    NOTE: <reject_cause> = 15 -> No suitable cells in tracking area <- At the airport !!
    NOTE: <ci> = 00607765 -> is also Vodafone, but now in Weg beim Jäger, Groß Borstel, Hamburg-Nord, Hamburg
    NOTE: why does the UE continue using Vodefone when Deutche Telekom is available?

    Test in Norway with Telenor eSIM:
    2020-02-05 07:27:10.021094 received 34 bytes from (‘’, 5592)
    A 08:29:23.459 “at+cereg?” sent
    A 08:29:23.459 "+CEREG: 5,1,“9F61”,“01027964”,9,“11100000”,“00001111” " received
    A 08:29:23.469 "OK " received
    NOTE: Successful receiption of message from UE with IP
    NOTE: <stat> = 1 -> Registered, home network
    NOTE: no <cause_type> or <reject_cause>

  • @inge-eriksen
    Hi Inge,

    all of our SIMs for M2M and IoT are G-SIMs, which means that technically they are always roaming. So a query for the registration state, for instance with AT+CEREG, should always yield: 5.
    On our testcards, we have currently no HPLMN deployed. For this reason the modem searches for a suitable network and will consider any NB-IoT network on the supported bands.
    To make sure that the modem will only connect to the DT network, you can either fall back to manual network selection (PLMN-Id=26201), or restrict the supported bands to band 8. This will exclude any operators in Germany for which we have not yet roaming agreements.

    Best regards,