Siera Wireless MP555, Руководство по установке программного обеспечения

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Rev 1.2 Jan.05 47
7 7: Using the Monitoring and
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UDP
UDP
MTP
Tracking Protocol
The RNAP Protocol
The MTP Protocol
This chapter describes the protocols used in data transmissions
between an MP 555 GPS modem and a network server,
providing the information necessary to develop host applica­
tions that process GPS and digital input data from a fleet of
MP 555 GPS modems. This discussion assumes that a
connection has been established between the modems and the
network server and that data is being received at the server.
This was covered in the last chapter.
All data sent from the MP 555 GPS is in the form of
packets. The GPS and digital input data is encapsulated within
the UDP packets and framed according to two Sierra Wireless
proprietary protocols, RNAP (Remote Network Access
Protocol) and MTP (Monitoring and Tracking Protocol).
Figure 7-1: Protocols used in data transmissions between the MP 555 GPS
and the network server
The host application must open a UDP socket through which it
receives the RNAP packets. It must then disassemble the
RNAP packets and the MTP packets to access the GPS and
digital input data. That data must then be parsed so that the
host application can process it to provide whatever infor­
mation the host application is intended to provide.
The next two sections describe the RNAP and MTP protocols,
providing the information necessary to disassemble the
packets and parse the data.
The RNAP Protocol
The RNAP protocol is designed to encapsulate several
different application protocols, of which only MTP is in use.
To allow for multiple application protocols, RNAP has been
designed with two layers: the packet layer, and the multi­
plexing layer.
Layer
RNAP
Packet Multiplexing
Layer
RNAP
Packet
Packet