SV 277 PRO User Manual
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available functionalities of the station remotely accessed.
The functionalities that a mobile modem offers are:
•
Main communication channel
•
SMS / E-mail alarms
•
SMS command exchange.
4.2.1. Main communication channel
Main communication channel is the TCP connection (a lossless data exchange protocol)
that can be used to exchange commands as specified by Appendix A to SVAN 977 User
Manual. + assures this connection and provides data download, performance
validation and measurement start/stop.
Main communication channel of SV 277 PRO can be established by one of two available
methods: TCP Client or TCP Server. The SV 277 PRO stations support SSL (Secure
Socket Layer) connections.
The
TCP Client
is a mode of main communication channel in which the mobile modem is
configured to initiate connection to a designated address (
remote host
). Each time a
reconnection period
(default value is 30 seconds) has elapsed, SV 277 PRO attempts to
establish a TCP connection to a designated address on a designated port (
Data Port
).
Should the connection be established successfully, SV 277 PRO can exchange
commands as in TCP Server mode. Should the connection attempt fail or is broken by the
remote host
, SV 277 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 mobile 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.
SV 277 PRO uses the TCP Client mode for connection with SvanNET (this is the default
setting of SVAN 977). The user PC connects to SvanNET via a web browser or
+, and the service creates a "bridge" between the station and the user PC. In this
case, the user does not need to buy more options for SIM card (public dynamic or public
static IP addresses are typically optionally payed and often hard to obtain). The essence of
SvanNET is to simplify the procedures and requirements necessary for the connection.
TCP Server
is a mode in which the mobile modem is configured to act as a server for
incoming connections. The modem is waiting for the first connection to be established on a
designated port (called
Data Port
; default 8001). Such connection can come from any
application - an initiator of the TCP connection (such as +) called
remote peer
.
This mode is recommended as it gives the initiative to the application. This mode requires
the SIM with a
public address
(also called
public IP
).
The
TCP Server
mode uses a so-called
Registration
. This is a method of translation of a
