CS-GSM/GPRS Digital Transceiver Kits (including the COM110 modem)
It is important to ensure you are aware of the likely costs of GPRS data transfer.
Prices can range from £0.005 to £10.00 per Megabyte of data transferred. As it
can require in excess of 50 Kbytes of data per day to check and keep a GPRS
connection open, let alone transfer any data, it is important to find the right tariff
and realise the likely costs. Where an always on connection is required, a flat-rate
tariff will likely be more economic or you should at least negotiate a volume
discount tariff with your provider. In the UK it is now possible to buy data only
access for few GBP per month for several tens of MB data transfer.
Before using the system you need to know the APN server name of your provider,
plus your username and password to gain access to the GPRS IP services.
5.3 GPRS Modes of operation
5.3.1 Using systems with fixed IP addresses
If you have a fixed IP service it may be either with routing to a public internet
address or to a private fixed IP address that you connect to via a VPN tunnel.
If it is via a VPN tunnel please seek the advice from the SIM provider on how to
setup and use the VPN tunnel. The tunnel will need to be open and kept open
automatically if you wish to use Loggernet to call the logger automatically.
With a fixed IP address, once connected to the network the logger will be able to
accept incoming connections for the services you have enabled, e.g. Pakbus, ftp,
http. If you connect to the logger for normal datalogger communications (via the
Pakbus/TCP service port) the datalogger will automatically start to send beacon
messages once per minute to the device that called. This will hold the connection
open (which is useful as some GPRS providers will cut-off inactive connections)
and also ensures the connection is working, however this does incur data traffic
charges. (See the help within Loggernet for connecting via an IP port – the port
number must match that set for the Pakbus/TCP Service port set in the logger.)
With a fixed IP address, Loggernet should be able to call out to the logger on
demand so it is possible to setup scheduled data collection. To minimise data
charges you can prevent the extra traffic outside the scheduled calls by unchecking
the box on the Pakbus port that forces it to stay open.
With a fixed IP it should also be possible for multiple PCs to call the same logger
either for data collection or connecting to the logger’s web or ftp server functions.
If you choose to do this though be careful to ensure the logger has an adequate
power supply to support multiple and lengthy connections and also check that you
are certain the traffic costs will not get out of hand. If calling the datalogger from
multiple PCs that use the Pakbus protocol please make sure that Pakbus port of
each copy of the calling software has a unique Pakbus address.
If using the TCP/IP function in the modem only one simultaneous
connection is possible at any time.
5.3.2 Using systems with dynamic IP addresses
For a few networks even though the datalogger has a dynamic IP address which
can vary on each connection, it is a public IP address so can connect to it from the
public internet if you can track the address assigned to it. It is possible to use a
dynamic name service in this instance (please contact Campbell Scientific for
more details).
NOTE
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