Sierra Wireless DART 200 CDPD Modem - Manual (Page 56)

DART 200 CDPD Modem User’s Guide 5 DART Supported Protocols
Sierra Wireless, Inc. 5-2
While UDP offers the possibility of using fewer data packets and less
total bytes to implement an application than TCP, adding the features
already described can consume some of these savings, and requires a
major programming effort.
The DART 200 provides basic UDP, available since the DART was first
commercially available, and the UDP server, which become available
with firmware version 3.0.4 for the DART in April, 1996. These are
described separately in the following subsections to delineate the setup
options and functions available with each.
Basic UDP characteristics
Basic UDP was originally offered on the DART 100 and early versions
of the DART 200. It provides a simple UDP communications capability
characterized by no server (auto answer) capability, and the need for both
sides of the communications session to use a common port number.
Without server capability the DART 200 issues a UDP dial (ATDP)
command to get into an online state so that it can receive incoming
datagrams.
Basic UDP communication
Before initiating UDP communication register the DART 200 on the
Cellular Digital Packet Data (CDPD) system. Refer to Channel
acquisition, p. 2-10, and Registration, p. 2-15, for instructions on
registering the DART 200.
To initiate UDP communication:
1. Basic UDP has no auto answer capability, so the modem must be in
online mode before communications can be started. Use the ATD
command with the P (for UDP) modifier followed by the IP Address
and port number of the destination system (host or another MC-
DART) to put the DART 200 into online mode. If the DART will be
used by a remote device that cannot issue a UDP dial command, then
basic UDP is not a viable option; the UDP server option must be
used.
2. If no port is specified the default port number (23) is used. Since the
DART listens by default if another DART is the target. If a port
number is required, specify it now. Unless the application operates
on a closed system, port numbers should be in the range between
1025 to 4999 to comply with industry standards.
Alternatively, the dial could reference an IP Address/port stored in
the DART 200 dial list by the ATDPSn command: where n is the
number of the desired IP Address in the dial list. Refer to Modem
dial directory, p. 8-24, or the &Z command in Appendix F, DART
AT Command Set, for more information.
? ?
NOTE:
The DART
implementation of basic
UDP requires that both
the host and MAS dial
commands use the same
port number.