Sutron Corporation Satlink Operations & Maintenance Manual, Rev 8.04.2 11/3/2016 pg. 149
15.10.1.
Course of Events
1.
Satlink connects to main or backup server.
2.
Satlink sends Session Type Code<cr> (see below.)
3.
Satlink sends Station Name<cr>.
4.
Satlink sends Report Type Code<cr> to indicate purpose of connection (see below.)
5.
Satlink sends transmission data (if any) in whatever format the user chose, such as SHEF or
pseudobinary.
6.
Satlink sends ETX (0x03) to mark end of data.
7.
Satlink sends a 3 byte pseudobinary encoded CRC16 of previous data and the server
password (sometimes called Shared Secret.)
8.
Server sends user login command !LOGIN=username,password<cr> and waits for Satlink
reply (ETX.)
9.
If user login matches, Satlink enters command-line session.
10.
Server issues pending commands, and Satlink processes and responds accordingly.
11.
When command processing complete, the server disconnects.
12.
If the server does not log in, Satlink will time out after 30 seconds and disconnect.
15.10.1.1.
Session Type Code
Session type defines the processing that occurs on connection. Currently, there is only one
session type, 0. This type is defined by the Course of Events above, and details that follow.
15.10.1.2.
Report Type Code
Report Type code describes the purpose of the transmission:
0 = self-timed
2 = entering alarm
4 = exiting alarm
6 = no data, command session only
15.11.
Iridium Telemetry Header
When Satlink sends data over the Iridium satellite network, it uses the header described below.
The header starts with a single byte in the ASCII printable range to make it easy to interpret the
content. Most transmissions will just have one header byte.
The header byte identifies the packet type in terms of the content of the packet, e.g., self-timed,
self-timed extended, entering alarm, entering alarm extended, etc.
Iridium modem buffers are limited in size. "Extended" types mean multiple packets are required
to transmit the entire message. Extended packets have information in the header that allows
