8application programming, At command set support – Sierra Wireless DART 200 CDPD Modem User Manual
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PN1197-00 Revision 1.0
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Application Programming
The Data Access Radio Transceiver (DART) 200 offers built-in
Transmission Control Protocol (TCP), User Datagram Protocol (UDP),
Serial Line Internet Protocol (SLIP), and telnet support, but most
end-user application programming that interacts with the modem uses
TCP, UDP, or SLIP.
Telnet is used primarily as a path to applications on remote hosts with
the local device being an ASCII terminal or, more likely, a PC emulating
an ASCII terminal. Outside of setting up the modem initially to meet
telnet’s needs, there is no programming to do. Error handling is provided
by the ASCII terminal emulator and is usually minimal.
This chapter is directed at TCP and UDP applications, and DART 200
solutions, particularly for DART 200 error handling. SLIP mode
applications function similarly, but the specifics are a function of the
capabilities of the software stack being used. If you plan on using SLIP,
refer to the application programming guide for your specific package.
AT Command Set Support
The terminal device, (Mobile Application Subsystem), does not have to
support the Attention (AT) command set directly to operate with the
DART 200. Even in cases where the device does support the basic AT
command set, there are some extensions to the command set that are not
supported. Usually, a programmable device can create a constant string
that represents the desired AT command. Sending such a character string
to the DART 200 works the same as sending the AT command.
If the remote device is of limited intelligence it does not need to support
the AT command set at all. The modem can be pre-initialized to work
with the remote device, including being in auto answer mode. In auto
answer mode, when the modem receives a connection request (TCP
mode), or a datagram (UDP mode), it goes online and passes data to the
attached device, just like a wire-line modem. In this situation, the fact
that CDPD is the communications medium is transparent to the remote
device.
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