2.5. Combination of IP and serial communication
RipEX enables combination of IP and serial protocols within a single application.
Five independent terminal servers are available in RipEX. A terminal server is a virtual substitute for
devices used as serial-to-TCP(UDP) converters. It encapsulates serial protocol to TCP(UDP) and vice
versa eliminating the transfer of TCP overhead over the radio channel.
If the data structure of a packet is identical for IP and serial protocols, the terminal server can serve as
a converter between TCP(UDP)/IP and serial protocols (RS232, RS485).
RipEX also provides a built-in converter Modus RTU – Modus TCP, where data structure is not the
same, so one application may combine both protocols, Modus RTU and Modus TCP.
2.5.1. Detailed Description
Generally, a terminal server (also referred to as serial server) enables connection of devices with a
serial interface to a RipEX over the local area network (LAN). It is a virtual substitute for the devices
used as serial-to-TCP(UDP) converters.
Examples of the use:
A SCADA application in the centre should be connected to the radio network via serial interface, however,
for some reason that serial interface is not used. The operating system (e.g. Windows) can provide a
virtual serial interface to such application and converts the serial data to TCP (UDP) datagrams, which
are then received by the terminal server in RipEX. This type of connection between RipEX and applic-
ation provides best results when:
•
There is no hardware serial interface on the computer
•
Serial cable between RipEX and computer would be too long. E.g. the RipEX is installed very close
to the antenna to reduce feed line loss.
•
LAN already exists between the computer and the point of installation
Note:
The TCP (UDP) session operates only locally between RipEX and the central computer, hence
it does not increase the load on the radio channel.
In special cases, the terminal server can reduce network load from TCP applications . A TCP session
can be terminated locally at the terminal server in RipEX, user data extracted from the TCP messages
and processed as if it came from a COM port. When the data reaches the destination RipEX, it can be
transferred to the RTU either via the serial interface or via TCP (UDP), using the terminal server again.
Please note, that RipEX Terminal server implementation also supports the dynamical IP port change
in every incoming application datagram. In such case the RipEX sends the reply to the port from which
the last response has been received. This feature allows to extend the number of simultaneously
opened TCP connections between the RipEX and the locally connected application up to 10 on each
Terminal server.
2.6. Diagnostics & network management
RipEX radiomodem offers a wide range of built-in diagnostics and network management tools.
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© RACOM s.r.o. – RipEX Radio modem & Router
RipEX in detail
