Applies To:
  • CitectSCADA 3.40

I am getting an error 'Wrong Sequence of Packets'. Sometimes shortly after this message the computer either hangs or crashes out to DOS. What is happening and how can it be fixed? 

This problem stems from Microsoft's implementation of NetBIOS. This only occurs with Windows for Workgroups and Windows 95. This problem does not exist with Windows NT. It has to do with using multiple receive NCBs when reading network information. Citect uses a default of 2 NCBs to read the NetBIOS information from the network. Sometimes when the Client is receiving a lot of network information these NCBs can be passed back to Citect in the wrong order. Citect picks this up and thus generates the above error. However at this stage Citect's networking is unstable and thus Citect may actually crash. The simple work around for this problem is to use only one NCB for receiving information. This is done by setting the following parameter in the Citect.ini file.


There may be a performance degrade but this has been measured to be nominally 5%, never more than 20% and sometimes no degrading effect at all.