Insys GPRS 5.0 serial 11-02-01-03-10.014 Manuale Utente
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11-02-01-03-10.014
INSYS GPRS 5.0 serial
Connection
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5.2.4 During the connection
5.2.4.1 Keep Alive
The data transfer via GPRS is packet-oriented. If no side of the
TCP connection sends data, there will be no traffic via the
transmission link. This also means that it can not be determined
if the remote terminal has disappeared without properly termi-
nating the connection (e.g. due to a failure of the radio network
or a failure of the remote terminal).
It can also happen that GPRS network providers terminate con-
nections themselves, if there is no data transfer for an extended
period of time, to be able to offer the resources to other partici-
pants.
For these cases, TCP offers a suitable accessory by sending Keep
Alive messages. The period between two monitoring packets can
be set to 1 minute steps (or be turned off completely). If three
successive monitoring packets are not responded to, the connec-
tion is regarded as terminated, and the INSYS GPRS 5.0 serial
returns to offline mode. If the device is configured as a leased
line device, the connection will then be re-established.
Keep Alive will mostly be used for leased lines, because the ap-
plication on location is usually not able to assume the connec-
tion control and monitoring.
The data transfer via GPRS is packet-oriented. If no side of the
TCP connection sends data, there will be no traffic via the
transmission link. This also means that it can not be determined
if the remote terminal has disappeared without properly termi-
nating the connection (e.g. due to a failure of the radio network
or a failure of the remote terminal).
It can also happen that GPRS network providers terminate con-
nections themselves, if there is no data transfer for an extended
period of time, to be able to offer the resources to other partici-
pants.
For these cases, TCP offers a suitable accessory by sending Keep
Alive messages. The period between two monitoring packets can
be set to 1 minute steps (or be turned off completely). If three
successive monitoring packets are not responded to, the connec-
tion is regarded as terminated, and the INSYS GPRS 5.0 serial
returns to offline mode. If the device is configured as a leased
line device, the connection will then be re-established.
Keep Alive will mostly be used for leased lines, because the ap-
plication on location is usually not able to assume the connec-
tion control and monitoring.
Alternatively, the settings can be entered or modified using the
terminal program.
Note: Keep Alive generates traffic; in principle, each Keep Alive
terminal program.
Note: Keep Alive generates traffic; in principle, each Keep Alive
packet is an empty TCP/IP message which must be con-
firmed. For one Keep Alive two empty TCP/IP messages
with 40 bytes each are required.
firmed. For one Keep Alive two empty TCP/IP messages
with 40 bytes each are required.
When selecting the timeout, besides ensuring that the connec-
tion is monitored, the pricing of the current GPRS contract must
also be considered.
tion is monitored, the pricing of the current GPRS contract must
also be considered.
see Chapter 8.8.3
Calculation example
AT**KEEP=<n>