5.8 NTCIP
LCom supports NTCIP via SNMP over LAN (Ethernet). The STMP protocol layer is
not supported.
In order to use NTCIP protocol with the LCom, the LCom must be connected via LAN
to the server. A GPRS/CDMA router/gateway can be used to connect the LCom
indirectly to the server/internet.
The TCP/IP port for SNMP (UDP port 161) must be redirected from the router to the
LCom.
Alternatively, an analog “dial in” modem for a PPP connection may be used (see
modem configuration).
The SNMP protocol on the LCom is based on the Microsoft SNMP library and is
implemented
by an “extension agent”. This extension agent (SnmpNtcipAgent.dll) is
called by the Microsoft SNMP framework when a request for an OID from the NTCIP
s
ubtree “iso.org.dod.internet.private.enterprises.nema.transportation” is received.
The agent is independent of the LCom application and starts as part of the Microsoft
SNMP protocol stack on Windows CE system startup. Various configuration and data
files are used as an interface between the LCom application and the agent.
The configuration files for the SNMP agent are managed via the corresponding
configuration dialogs in the LCom application and (as the other LCom configuration
files) are stored on the internal flash drive (\FFSDISK directory).
The LCom application periodically (whenever the USB device requests new
measurements
– that is every minute) writes the measurements (already converted
to the corresponding units for NTCIP) to a temporary file in the \Temp directory (i.e.
to the LCom RAM).
The LCom’s network configuration must be configured for the specific LAN
environment (IP address, default gateway, DNS server etc.). If the LCom is
connected via a GPRS/CDMA router and the Internet, the GPRS/CDMA router must
either work with a static IP address or must support DynDNS (or a similar service) in
order for the server to open a TCP/IP (SNMP) connection to the LCom.
