Sierra Wireless RAVEN 1X 20070914 - Manual (Page 67)

Data Communication and Host Modes
Rev 3.0B Feb.08 62
remote IP/port until no data is sent or received for the time
interval defined in the UDP auto answer time‐out (S83).
During this session, packets from other IP/port addresses will
be rejected, unless *UALL is set. Whether or not an incoming
packet will cause the modem to enter a UDP session is always
dependent on the S53 and AIP settings.
The Normal UDP Mode (MD3) can be combined with UDP
auto answer to cause the incoming serial data to be sent in
UDP packets (instead of being treated as AT commands), while
allowing sessions to be established from different UDP
sources. A UDP session will be initiated either by incoming
serial data or by an incoming UDP packet. The session, started
by either method, will be terminated when no data has been
sent or received for the S82 period. Once the session termi‐
nates, another may be initiated by either means.
When idle, after the time‐out has occurred, the modem is in AT
command mode on the serial port, and any valid AT command
may be entered during this time.
Tip: It is best to ensure the idle time-outs for TCP and UDP are never
0 if you're going to be using auto-answer, or either PAD mode. In
those circumstances, you will want the modem to close the socket if
the connection goes idle for too long, particularly if the other side
doesn’t normally close the connection.
When the session is initiated by serial data, the new session
will be established using the destination address specified in
S53. The S53 setting can be changed if the connect to last UDP
setting (*UDPLAST=1) is set. The address in S53 will be
updated to reflect the address of the last session initiated by an
incoming UDP packet. So that when new data is received over
the host serial port while in the idle state, a session will be re‐
established with the last address. (This behavior is the same as
the previous Hybrid2 (MD6) mode).
Tip: TCP auto answer (S0) may also be set simultaneously with UDP
auto answer. Then, when in the idle state, the modem will accept
either a TCP or UDP incoming packet, and enter a TCP or UDP
session as appropriate.
Reliable UDP
Reliable UDP adds a simple protocol on top of UDP to provide
reliable delivery of data. When data is received from the host
serial port, a 2 byte header is added to the data, containing a
message type and a sequence number. The Raven will continue
to send this data (buffering any received data in the meantime)