Sierra Wireless RAVEN 20070914 - Manual (Page 64)

Data Communication and Host Modes
Rev 3.0B Feb.08 59
• TCP auto answer is enabled (S1), a TCP connection request
is received, and the modem is not in a data session.
• Data is received on the serial port and
· The Startup Mode Default (MD) is 4 (auto TCP)
· The remote TCP destination, as defined in S53, success‐
fully responds to the TCP connection request.
The value of S7 (TCP Connection Time‐out) specifies the
number of seconds to wait, after initiating a TCP connection
attempt, for a successful connection to be established. If the
connection has not been successfully established before the
time‐out occurs, ERROR/BUSY is returned.
TCP packet assembly is affected by the values of S50 (PAD
Forwarding Time‐out) and S51 (PAD Forwarding Character).
Data received in the serial buffer will be transmitted when the
idle inter‐character time‐out specified in S50 (in tenths of
seconds) occurs or when a character is received that matches
S51 (if non‐zero).
The TCP session will be terminated if no data is transmitted or
received for the time interval specified in TCPT and TCPS.
TCPT is the number of minutes (TCPS=0) or seconds (TCPS=1)
used for this idle time‐out.
Caution: TCPT should never be 0 when using the TCP mode. A
broken TCP session can result in the modem being left with a TCP
half-open connection that can only be terminated with a reset.
TCP Auto Answer
TCP auto answer (S0=1|2) also allows a TCP connection
request to be “answered” when the modem is idle, not in a
data session. The TCP connection requestʹs destination port
has to match the modemʹs device port.
Note: UDP auto answer may also be set simultaneously with TCP
auto answer. Then, when in the idle state, the modem will accept
either a TCP connection request or UDP incoming packet, and enter a
TCP or UDP session as appropriate.
Hybrid Modes
Hybrid modes are supported mainly for legacy implementa‐
tions. Some previous hybrid modes (MD=5, 6) are no longer
implemented as special, unique modes. Now that UDP auto
answer (UDP Half‐open, S82=2) can be enabled in conjunction