Technical information

Remote AT+i Service
2-100 AT+i Commands Reference Manual May 31, 2008
Remote AT+i Service
Introduction
The LATI parameter allows configuring W24 to maintain a communication channel that supports
interacting with W24 from a remote location using the AT+i command set as if the commands are
administered through the local serial port. When LATI is set to a non-zero value, W24 opens a
TCP listening socket on port <LATI>. In a dial-up environment, this occurs only after the PPP
connection is established. This listening socket can be used to connect to W24's remote AT+i
service.
Remote AT+i Commands
When a remote client connects to W24's LATI socket, W24 redirects the socket's data flow to the
AT+i parser, in effect allowing the socket to take over the parser. Any data coming from the
socket is processed by W24 as if it came from the host serial port and the replies are returned to
the socket instead of being sent to the host serial port. W24 replies with an I/BUSY to commands
coming from the host serial port, while the remote client is connected.
An exception to this is the (+++) escape sequence. On detection of (+++) from the host serial
port, W24 closes the remote connection and reboots.
If W24 was in the process of performing some Internet activity initiated by the host at the time the
remote client connected, W24 allows this activity to end and the final reply to reach the host
before passing control over the parser to the remote client.
Closing a Remote AT+i Session
To close a remote AT+i session, the remote client can choose to issue AT+iDOWN via the socket.
In response to this, W24 restarts. Only I/OK is returned over the socket before it is closed by
W24. Alternatively, the remote client can close the socket in order to disconnect, leaving W24's
Internet session as-is. In the latter case, W24 returns control over the parser to the local host port.
The LATI listen remains active, available to service additional remote connections. After a LATI
session is closed, the LSR (last session error) web parameter contains the value 096 to indicate
that a LATI session has been disconnected.
Note: (+++) sent over the LATI socket is not recognized as an escape sequence.
Caveats and Restrictions
• When W24 in dial-up mode is in auto baud rate detection mode (after re-starting with
BDRF=a or in response to the AT+iBDRA command), a remote AT+i session cannot be
established, even if the LATI parameter contains a port value.
• In W24 WLAN the remote AT+i service is available, even if W24 WLAN is in auto baud rate
detect mode. However, once the remote AT+i connection is established, W24 WLAN will no
longer be in auto baud rate mode and the host will be able to send the (+++) escape sequence
only at 9600 baud, if it needs to close the remote session. W24 WLAN will then return to
auto baud rate detect mode when and if the local host or the remote client close the LATI
session, in effect re-starting W24 WLAN.