Sutron Corporation X-Link Operations & Maintenance Manual, Rev 1.63 5/24/2016 pg. 153
16.
Data Formats
16.1.
TCP/IP Session
GPRSLink, HSPALink, and CDMALink use scheduled transmissions periodically
connect to a server and deliver sensor data. See the Cell Phone Telemetry and
Cell Phone Settings sections for more details, beginning on page 95
.
Relevant settings include
Main Server, Backup Server, Server Port, and Server
Password.
When GPRSLink, HSPALink, and CDMALink connect to a server, some information
is sent to the server before the sensor data is delivered. This information is
meant to help the server decide what to do with the sensor data that is en route.
The information includes details such as the sensor name and whether the
transmission is a result of an alarm event.
After the sensor data is delivered to the server, the server may log into X-Link
and issue commands to check status, change setup, download more data, or any
other command line activity.
16.1.1.
Course of Events
1.
X-Link connects to main or backup server.
2.
X-Link sends Session Type Code<cr> (see below.)
3.
X-Link sends Station Name<cr>.
4.
X-Link sends Report Type Code<cr> to indicate purpose of connection (see
below.)
5.
X-Link sends transmission data (if any) in whatever format the user chose,
such as SHEF or pseudobinary.
6.
X-Link sends ETX (0x03) to mark end of data.
7.
X-Link 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 X-Link reply (ETX.)
