Monitoring Station SV 279 PRO
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4.2.
Interface functionalities of 3G modem
The 3G modem enables the user a wide spectrum of interfacing capabilities using GSM
based internet access.
Internet access, provided by GSM operators, comes with a set of parameters that
define the visibility of the SIM card address in the network. This address can be
public
or
private
(accessible from the outside or not) and can be
static
or
dynamic
(same or
different each time the card connects to the Internet). The set of parameters define the
spectrum of available functionalities of the station remotely accessed.
The functionalities that 3G modem offers are:
•
Main communication channel
•
SMS / E-mail alarms
•
SMS command exchange.
4.2.1.
Main communication channel
Main communication channel is a TCP connection (a lossless data exchange protocol)
that can be used to exchange commands as specified by Appendix A to the SVAN 979
User Manual. + assures this connection and provides the most accurate and
real-time method of performing data download, performance validation and
measurement start/stop.
Main communication channel of the SV 279 PRO can be established by one of two
available methods: TCP Client or TCP Server.
The
TCP Client
is a mode of main communication channel in which the 3G Modem is
configured to initiate connection to a designated address (
remote host
). Each time a
reconnection period
(default value is 30 seconds) has elapsed, the SV 279 PRO
attempts to establish a TCP connection to a designated address on a designated port
(
Data Port
). Should the connection be established successfully, the SV 279 PRO can
exchange commands as in TCP Server mode. Should the connection attempt fail or is
broken by the
remote host
, the SV 279 PRO will attempt to connect again after
another reconnection period has elapsed.
To prevent the connections from going
idle
(a state in which the connection seems
active, but no data can be transferred
– it may happen due to GSM operator terminating
the link, but the TCP protocol not being able to detect it), the station maintains the
connection to the server by sending small packages of data at reconnection period
(which by default is one minute). If the transfer is not properly acknowledged by the
other party, the connection will be terminated.
Note: TCP Client mode is used in the SvanNET service.
The SV 279 PRO uses the TCP Client mode to connect to SvanNET (this is the
default setting of the SVAN 979). The user also connects to SvanNET via web browser
or +, and the service creates a "bridge" between the station and the user. In
