Sierra Wireless DART 200 CDPD Modem - Manual (Page 146)

DART 200 CDPD Modem User’s Guide F DART AT Command Set
Sierra Wireless, Inc. F-2
Table F-1. Commands beginning with letters
A/ Repeat
Repeats the last AT command.
NOTE:
An AT is not required preceding this command.
A Answer Online
Causes the DART to stop accepting commands and to wait for an incoming connection request on the
active listening port (see also, *L command) for the amount of time specified in S Reg 7 (default - 20
seconds). If a pending connection request (Ring) is already present, the DART accepts the connection
and enters the online state.
Usually issued in response to the RING message generated by a connection establishment request
(Dial) from a TCP client, or the initial incoming data packet from a UDP client. For TCP the
reception of the initial SYN packet from the client initiates the RING.
Any following commands on the same command line are ignored. If input is detected prior to
entering online mode, the command is aborted.
After the incoming call is answered, either by an ATA or by setting S-Register 0 = 1, the source
address of the caller (IP Address and port number) is available in S-Register 53 and can be viewed by
an ATS53?. It cannot be determined by performing an AT&V and viewing S-Register 53.
NOTE:
The preferred method of responding to an incoming connection request is to have the modem in
permanent auto-answer mode (by setting S-Register 0 = 1).
Format:
ATA
Answer online
Result codes:
CONNECT
Connection is established
NO CARRIER Connection not established due to time-out
ERROR Connection already established
D Dial (connection setup)
Issued by a client device to establish a communication session with a server device. What actually
occurs depends on whether a TCP (also telnet) or a UDP session is being initiated.
For TCP (or telnet) the DART accepts a connection setup request containing a destination address
and optional port, validates it, transmits it to the network, and waits for a response from the server
device.
For a DART server an incoming connection request causes a RING message to be generated. If
auto answer is not specified by setting S-Register 0 = 1, the Ring message is repeated every 10
seconds for a total of 60 seconds. If the call is not answered by the server (either automatically or
with an ATA) within the 60-second time period, a NO ANSWER message is returned to the TCP
client.
For UDP the DART accepts the connection setup request, validates it, and stores the destination and
optional port number for later use and enters online mode. However, at this point the server is
unaware of the UDP Dial. No communication with the UDP server occurs until the client sends a
data block to the modem. The data will be combined with the previously stored destination address
and transmitted to the network for routing to the UDP server.