The setup:

    - I am using Osmo-MSC, Osmo-HLR, python-smpplib, and sim-tools. My SIM card is a Sysmocom USIM-SJS1 which came with OTA keys.

    - Osmo-MSC has been configured to accept SMPP connections, and dcs-transparent has been set.

    - Using sim-tools with the --smpp flag, I generated the necessary SMPP messages to load the HelloSTK.cap file to the SIM. (Essentially, I've followed the instructions here: https://osmocom.org/projects/cellular-infrastructure/wiki/Shadysimpy)

    - Sim-tools outputs 6 messages, so in a separate program I use python-smpplib to push each message to the MSC over SMPP.

    - The send function in my program looks like this:

parts = ["027000003815060115150000001dbf31df8eb85248617ff79260f7bf0abd332e2b3c>
         "02700000901506011515000000d85420f0f778e35b4b8e0ae5d961593444f20fdebb>
         "02700000901506011515000000729062e3cc920acc51be4f22fd067314bfaee313d6>
         "02700000901506011515000000373f30a3c12b494d3089c70a2dd46e33e3fccac790>
         "0270000068150601151500000083f04c39ef2df571bd5389f71b8c528e9b3edea046>
         "02700000601506011515000000ad6eeebc9373de8bd3a8888324ffaad4d8cd935f0c>
         ]
for part in parts:
    pdu = client.send_message(
        source_addr_ton=smpplib.consts.SMPP_TON_INTL,
        source_addr='0',
        dest_addr_ton=smpplib.consts.SMPP_TON_INTL,
        destination_addr='3331112222',
        short_message=bytes.fromhex(part),
        data_coding=246,
        esm_class=64,
        registered_delivery=True,
    )
    print(pdu.sequence)

 

I have Wireshark running on the computer hosting the MSC, and it shows GSM SMS messages sending to the UE, however there is no response, and when I inspect the SIM card, no applet has been loaded.

Am I missing something here? What could be causing this issue?

Thanks!