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Data Communication and Host Modes
Raven EDGE/GPRS for Cingular - User Guide, version 2.31
UDP Multicast mode results in any data received from the host serial port being sent to all the cli-
ents in the address list. The remote port number is taken from S53. To avoid flooding the network,
the packets are sent to each client with a 20ms pause in between. The receipt of UDP packets
works as in normal UDP mode (i.e. bound by the value S53 and/or AIP). Since it may take a while
to transmit the data to all hosts (especially if all 20 Modbus entries are used and name resolutions
are required), new data received from the host port is buffered until current transmissions to all
hosts are finished.
Enter the list of target IPs in the address list (ADDR LIST). The index numbers in the list aren't
used. Configure for a normal UDP session. Set the Startup Mode Default to 83 (ATMD83). Con-
figure the Destination port to match the device port of the remote modems.
TCP PAD
When the Raven is in a TCP session, all characters received on the serial port are assembled into
TCP packets and sent to the mode's remote IP address/port, and any packets received from the
remote end of the TCP connection are disassembled and dumped onto the serial line.
A TCP connection is established by one of the following methods:
•
Using the Dial TCP (DT) AT command (for example, ATDT192.168.3.23/3456)
•
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, successfully responds to the TCP connection
request.
The value of S7 (TCP Connection Time-out) specifies the number of seconds to wait, after initiat-
ing 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 spec-
ified in TCPT and TCPS. TCPT is the number of minutes (TCPS=0) or seconds (TCPS=1) used
for this idle time-out.
TCPT should never be 0 when using the TCP mode. A broken TCP ses-
Caution:
sion 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 request's destination port has to match
the modem's device port.
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