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PinPoint-E EDGE/GPRS - User Guide, version 2.32 27
Data Communication and Host Modes
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 mes
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sage type and a sequence number. The PinPoint-E will continue to send this data (buffering any
received data in the meantime) until it receives an acknowledgement with this sequence number.
If an acknowledgement is not received within the time-out period (specified in S7), the data will
be retransmitted. This will continue until an acknowledgement is received or the modem is reset.
Likewise any UDP packets received by the PinPoint-E are expected to have this simple header.
The PinPoint-E will issue an acknowledgement for any valid packets which are received.
To configure the PinPoint-E for a normal UDP session, you need to set the Startup Mode Default
to 73 (ATMD73). If you are using two modems, configure the Destination IP and Port in each to
point to each other. Serial data will then be sent reliably between the two.
Note: Although it adds reliability, the simple implementation of the Reliable UDP
mode in the does not check for duplicate packets.
UDP Multicast Mode
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
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figure the Destination port to match the device port of the remote modems.
TCP PAD
When the PinPoint-E 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.