From Technologic Systems Manuals

The sbdctl application is an example application that can send and receive data on the IRIDIUM network. It requires an IRIDIUM 9602 modem and an appropriate account through a third-party satellite network provider. The source code example is located on the Technologic Systems public github here.

The sbdctl application uses multiple command line switches, and uses stdin/stdout where input or output are necessary:

root@ts7800-v2:~# sbdctl 
Usage: sbdctl [options] ...
Technologic Systems SBD Control Utility
Status output goes to stderr.  All other IO uses stdin/stdout.
Options are executed in the order given on the command line.
For example:
sbdctl -D <data_len_bytes> -c < myfile.bin
This would read myfile.bin into the MO buffer, then initiate an SBD session
(if possible) to transmit the data to the network.
NOTE:  Maximum input is 340 bytes for either text or binary transmissions.
NOTE2:  The MO and MT buffers can only contain one message each.

 -p, --port </dev/ttyEX1>  Define which serial port to use.
 -c, --connect             Connect to satellite and initiate SBD session.
 -t, --tread               Read text from SBD modem's receive buffer.
 -d, --dread               Read binary data from SBD modem's receive buffer.
 -T, --twrite <len>        Write <len> bytes text data from stdin to SBD modem's transmit buffer.
 -D, --dwrite <len>        Write <len> bytes binary data from stdin to SBD modem's tx buffer.
 -r, --rssi                Request new RSSI reading from SBD modem.
 -s, --status              Get local MO and MT message queue status.
 -e, --events              Enable unsolicited event reporting from modem.
 -i, --info                Dump modem-related info in BASH-compatible variables.
 -x, --indexes             Report message index number for MO and MT.
 -y, --clearindex          Clear Mobile Originated Message Sequence Number.
 -k, --clearbuffers        Clear both MO and MT buffers.
 -l, --clearmobuf          Clear Mobile Originated (MO) buffer.
 -m, --clearmtbuf          Clear Mobile Terminated (MT) buffer.
 -a, --cpymomtbuf          Copy MO to MT buffer on modem.