DART 200 CDPD Modem User’s Guide | 8 Application Programming |
4.For a modem functioning as a server, (answering calls or being polled) activate the appropriate server, TCP (with AT*A1) or UDP (with AT*A2). The connection can be established automatically by having auto answer active
For both client and server systems, successful completion of the Dial command (ATD) is indicated by a CONNECT message (verbose mode) or a 1 (terse mode). This puts the modem in online mode. In this state, AT commands are ignored, the autobaud function is suppressed, and flow control (if specified) is enabled.
Data transfer
To accomplish data transfer, the DART 200 must be in online mode. Data transfer is performed by the Mobile Application Subsystem (MAS) by sending data to or reading data from the DART 200’s
Outgoing data accumulates in the DART 200 until a data forwarding condition is reached. The DART 200 then attaches the appropriate header information, and sends the data onto the CDPD network for forwarding through the appropriate routers to the target IP Address and port. Refer to Data forwarding, p.
The incoming packet is received by the DART 200, and the header is removed, and the data passed, subject to flow control considerations, as described on p.
Modes of operation
A major difference between a Cellular Digital Packet Data (CDPD)
AT commands are issued and responded to by the DART 200 when in command mode. Once a remote station is dialed, or SLIP mode is started, the modem enters online mode and only transmits or receives data; it no longer responds to AT commands.
To return to command mode, to process AT commands for error recovery purposes or to hang up at the end of a session, the DART 200 issues an escape sequence, or drops Data Terminal Ready (DTR) (if possible) with an &Dn set up option specified. Refer to Escaping through the control interface, p.
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