Applies To:
  • CitectSCADA 4.xx, 5.xx
Summary:
I need to connect Citect on Windows NT to multiple serial devices and would also like to implement redundancy if possible.  I have heard about the LantraServer from Stallion Technologies - does CiT know anything about this product?  How do I configure it to work with Citect? 

Solution:
The LantraServer comes in two flavours (8 port RS-232 serial OR 4 port RS-232 + 4 in-built modems).

The LantraServer Extend software that comes with the unit installs some software (an NT Service) on NT Workstation or NT Server (does not work on 95).  This service manages a number of virtual com ports on that PC.  To Citect these virtual com ports look no different than a physical one so Citect configuration is very simple (i.e. as if it was connected directly to the com port on the back of the PC).

The virtual com ports are now set up on one or more NT machines and are mapped (via the Extend software) to Pools within the LantraServer device. Each pool has one physical com port on the LantraServer, hence each virtual com port ends up being directed to a serial device connected to a com port on the LantraServer.

The reason for the pools in the LantraServer is to allow it to handle contention for the com port and hence support redundancy.  However since serial communications is point to point, then when ever an NT machine has a connection through to the serial device the other (redundant) communications path (i.e. the other NT machine) comes up as "unit offline" because it cannot get a connection. But if the first communications path fails then the second NT machine gets a chance to make a connection and bring communications back on online.

At the end of the day if you just have a single Citect I/O Server and want to talk to serial devices located remotely then this unit is perfect. If you want I/O Server redundancy to the serial devices then this unit can solve this, with the slight drawback that you will get hardware alarms for the standby I/O Server that can't get through.

The LantraServer itself is very easy to configure. The Extend software is fine and is only required for configuration (the virtual com port stuff is done as an NT service in the background). Currently it is best to use version 1.10 of the Extend software as Version 1.20 seemed to cause problems with Citect. The operation of this system is protocol independent as it doesn't care what data is going through. Therefore it will in most cases support all Citect protocols that can go over a serial cable.

 
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