User guide
Table Of Contents
- Guarantee
- Contents
- CS-GPRS Communications Package
- 1. Introduction to GPRS
- 2. Hardware
- 2.1 Power use considerations
- 3. Network Contract and SIM card
- 4. Datalogger firmware
- 5. PC Software required
- 6. Basic Datalogger setup
- 7. General Principles of Operation
- 7.1 Using systems with fixed, public IP addresses
- 7.2 Using systems with dynamic IP addresses
- 7.3 Keeping the connection open
- 7.4 Firewall issues
- 7.5 Minimising call costs and power use
- 7.6 Calling the logger in GSM data mode
- 8. Fault finding
User Guide
9
7.3 Keeping the connection open
Once a connection between the logger and the Loggernet PC is established,
Pakbus messaging will keep the port open and allow Loggernet to make outgoing
calls to the logger, e.g. via scheduled data collections. Note, for the connection to
stay open you must set the Pakbus port to be always open (but do not set this
setting if the logger is making less frequent call-back connections controlled by
code in the logger to conserve power).
Whether operating in call-back or fixed IP mode if no valid TCP/IP packets are
received by the datalogger within a few minutes, it will test the PPP link locally
using a special PPP link test that most providers support. If that fails or 30
minutes pass with no real data being transferred it will then try to ping a local
DNS server, if that fails it will attempt to hang up the PPP connection and redial.
This process allows detection and recovery from a broken GPRS connection
(which is not uncommon on some networks).
As the disconnect/reconnect process takes 10-15 seconds and has to be allowed for
when restarting a connection from Loggernet, i.e. the logger will not appear to be
online immediately. Furthermore, in the rare event that the connection is broken
in an unexpected fashion, it can take up to five minutes for Loggernet/Windows to
time out an open socket before it is ready to accept a new incoming connection.
In exceptional circumstances when there is say a network fault, it could take the
datalogger over 30 mins to detect a fault and recover the connection. Please be
aware of such delays when checking for and debugging lost connections. If you
have a poor connection it is possible to speed up the detection of loss routing back
to Loggernet by adding code to the logger program, please contact Campbell
Scientific Ltd for further details.
Once a connection is established Loggernet will keep the connection open and
active. If you are not using Loggernet for Pakbus communications, e.g. you are
collecting data by FTP, you either need to poll using FTP at an interval less than