Applies To:
  • CitectSCADA x.x
Summary:
I am trying to get a remote Citect machine connecting via RAS with a leased line to an operational Citect network. Are there any tips to getting this working? 

Solution:
There are a few issues to be considered here. Even though Microsoft are reluctant to guarantee that RAS over a leased line will work, it can be made to go. Here are some cases.

Similar O/S: RAS will connect from NT to NT using a null modem cable. When you're setting it up you have to choose the correct modem; I think it's called Direct cable connection in the modems list. You simply need to install the RAS software and start the server service on one, and use the other as a client. WFW has a similar setup and it allows you to choose a null modem as your modem type. With Win95, there is a separation between using a dial up line (via PSTN) and using a direct cable connection. However, Win95 to Win95 works okay.

The problems begin when you try to connect cross platform using a null modem. To connect a WFW machine to an NT machine you should configure a null modem at the WFW end and a direct cable connection at the NT end. Also, you must ensure that the maximum speed on the NT remote access server matches the top speed of the modem on the WFW machine. I recommend 9600 baud. We have successfully established a connection of this type at 19200 baud but it seemed to be a bit unreliable.

Remember also that Citect may have trouble establishing connections to other computers over RAS due to NT's treatment of NetBIOS names. See Q1174 for more info on this.

 
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