Multisocket AT CMD – SendUDP failure

5 thoughts on “Multisocket AT CMD – SendUDP failure

  1. Hello,

    I just start playing with Telit GL865QUAD. 

    I try to use Multisocket AT commands since those are the only one that can provide working in command mode for UDP/IP communication. 

    Receiving data is fine but I have problems with sending.

    I start with a master reset, then go for GSM, attach to GPRS, activate PDP, Socket Dial and then SSEND and SSENDEXT, but last 2 function fail.

    There are no data over network at server site (172.20.165.66). I monitor with tcpdump on router and wireshark on server. I’m able to see ping from and to module, I can receive UDP datagrams and read on Telit side but nothing when send from Telit.

    Below are AT commands:

     

    at+CMAR="00000000"

    at#cgmi
    #CGMI: Telit

    OK
    at#cgmm
    #CGMM: GL865-QUAD

    OK
    at#cgmr
    #CGMR: 10.00.144

    OK

    at
    OK
    at+cpin?
    +CPIN: READY

    OK
    at+cgatt?
    +CGATT: 0

    OK
    at+cgatt?
    +CGATT: 1

    OK
    at+cgdcont=1,"IP","privateAPN"
    OK

    at#sgact=1,1
    #SGACT: 10.96.120.148

    OK

    at#sd=1,1,6996,"172.20.165.66",0,32768,1
    OK
    at#ssendext=1,4
    > 1234
    OK

    SRING: 1
    at#srecv=1,1500
    #SRECV: 1,5
    test

    OK

    at#ss
    #SS: 1,2,10.96.120.148,32768,172.20.165.66,6996
    #SS: 2,0
    #SS: 3,0
    #SS: 4,0
    #SS: 5,0
    #SS: 6,0

    OK
    at#si
    #SI: 1,4,5,0,0
    #SI: 2,0,0,0,0
    #SI: 3,0,0,0,0
    #SI: 4,0,0,0,0
    #SI: 5,0,0,0,0
    #SI: 6,0,0,0,0

    OK

    1. Is this a VPN? I see your server has 172.20.165.66 which is a private address, probably behind a router/firewall so cannot be reached from the outside Internet.

       

      1. It is one of the biggest VPN (APN) between GSM operators in UE. All SIM’s work with another GRPS module manufacturer. I’m testing functionality of Telit in order to decide if switch or not to Telit. There is not a question of firewall between SGSS-GGSN and our routers and servers since with other type of GPRS module we are able to successfully send and receive UDP datagrams on same IP protocol (UDP) and same source and destination port’s.

         

        On the other side, did Telit have some "debugging" at radio link level protocol (read and decode communication between Telit and serving GSM CELL? 

        This can be an example:

         

          804|00:00:00.000| 271447|  —  |   SM> 
        GMM|TRA_SYS_SEND_TO_PC          |MMSM_UNITDATA_REQ          
        |ACTIVATE_PDP_CONTEXT_REQUEST

             57 24 04 00 02 00 1B 00 10 00 28 10

             E0 F2 18 A8 43 00 00 00 00 00 43 00 00 00 DE 10 00 00 13 00 0A 41
        0F 00 00

             0A 41 05 03 0B 00 00 1F 00 00 00 00 00 00 00 00 02 01 21 28 0F 04
        73 65 6B

             61 06 63 6F 6E 6E 65 78 02 72 6F 27 1D 80 C0 23 06 01 5F 00 06 00
        00 80 21

             10 01 60 00 10 81 06 00 00 00 00 83 06 00 00 00 00 18 FF

             t_mmsm_UnitDataReq

               p_SmPduPtr = 0xA818F2E0 (2820207328)

               v_SmPduLength = 0x43 (67)

               v_FrameTrace = 0

             ExternalInfo =

              ====================================

             |       Beginning of decoding        |

              ====================================

             Message Length : 560

             ff > 1111111-  07 bit(s)  [– TRACER_MESSAGE: 0x7f –]

        >>>> TRACER_Messages

             ff > ——-1  01 bit(s)      [– Uplink: 0x01 –]

             0a > 0——-  01 bit(s)      [– TI_Flag_or_Skip_Ind_first_bit:
        0x00 –]

             0a > -000—-  03 bit(s)      [– TIO_or_Skip_Ind_3_last_bits:
        0x00 –]

             0a > —-1010  04 bit(s)      [– PD: 0x0a –]

        >>>> GPRS_SM_Message_Uplink

             41 > 01000001  08 bit(s)          [– MT: 0x41 –]

        >>>> Activate_PDP_context_request

        >>>> Requested_NSAPI

        >>>> spare_half_octet

             05 > 0000—-  04 bit(s)                      BE0 = 0x00 (0)

        <<<< spare_half_octet (4 bits)

        >>>> NSAPI_value

             05 > —-0101  04 bit(s)                      [– NSAPI_5: 0x05 –]

        <<<< NSAPI_value (4 bits)

        <<<< Requested_NSAPI (8 bits)

        >>>> Requested_LLC_SAPI

        >>>> spare_half_octet

             03 > 0000—-  04 bit(s)                      BE0 = 0x00 (0)
        … and so on …

          1. That problem was solved, there was a issue in ip_conntrack in one of our servers. Sendig UDP work like a charm.

            Thanks.