User's Manual

22 MDS Mercury 16E Technical Manual MDS 05-6302A01, Rev. A
Dual Purpose
Capability
The transceiver's COM1 serial port is able to function as a local console
or in data encapsulation mode. When the
Com 1 Status parameter is set to
Enabled, the port operates in data encapsulation mode. It can be reverted
back to console mode by entering the escape sequence +++ at the data
mode baud rate.
TCP and UDP
Encapsulation
The serial data can be encapsulated in either TCP or UDP packets. TCP
provides a connection-oriented link with end-to-end acknowledgement
of data, but with some added overhead. UDP provides a connection-less
best-effort delivery service with no acknowledgement.
Most polled protocols will be best served by UDP service since many of
these protocols have built-in error recovery mechanisms. UDP can
provide the needed multi-drop operation by means of multicast
addressing.
On the other hand, TCP services are best suited for applications that do
not have a recovery mechanism or error-correction but need the
guaranteed delivery that TCP provides while affording the extra
overhead required.
Serial Encapsulation Transparent encapsulation, or IP tunneling, provides a mechanism to
encapsulate serial data into an IP envelope. In operation, all of the bytes
received through the serial port are put into the data portion of a TCP or
UDP packet. In the same manner, all data bytes received in a TCP or
UDP packet are output through the serial port.
When data is received by the radio through the serial port, it is buffered
until the packet is received completely. There are two events that signal
an end-of-packet to the transceiver: a period of time since the last byte
was received, or a number of bytes that exceed the buffer size. Both of
these triggers are user-configurable.
One transceiver can be used for IP-to-serial encapsulation in which it
communicates with another IP-based device. On the other hand, two
transceivers can be used to create a serial-to-serial channel using TCP or
UDP between them.
TCP Client and
Server modes
A TCP session has a server side and a client side. You can configure the
transceiver to act as a server, a client, or both.
TCP servers listen and wait for requests from TCP clients to establish a
session. A TCP client is an application running on a device somewhere
on the network. TCP clients actively attempt to establish a connection
with a TCP server. In the case of the transceiver, this happens whenever
data is received on the serial port.
The transceiver can also operate in Client/Server mode in which it
operates in either client or server mode, depending on which event
occurs first; either receiving data on the serial port, or receiving a
request to open a TCP connection from a remote client.