Applies To:
  • CitectSCADA 1.00 1.01 1.10 1.11 1.20 2.00 2.01

The error message "Cannot Open Server <name> NetBIOS Error <x>", where the <name> is the name of the server and <x> may be 0, 11 or 14 can be caused when Citect runs out of sessions table slots. If this error occurs at startup of a server then the error message is most likely correct. If this error occurs after the Citect server has been running for a long period of time or a few minutes after startup or when you add a new Citect Client on the network, then Citect has most likely run out of sessions table slots. 

When Citect runs out of session table slots it will cause a fatal network error and Citect will shutdown. In Citect for Windows Versions 2.10 and earlier this error was incorrectly reported as the Cannot Open Server NetBIOS Error. In later versions this error is reported as "Out of Msg Instance, Increase [LAN]Sessions".

To solve this problem you should increase the number of sessions in the CITECT.INI file via the [LAN]Sessions parameter. This parameter will default to 64 (128 in version 3.0 and later) and you should increase until this error does not occur.


You may calculate the number of session table slots needed by counting the number of Citects on your network, times the number of Servers this computer is, plus the number of I/O Servers. For example if you have 20 Citect computers and this computer is a alarm, trend, report server and you have 3 I/O Servers you get 20 x 3 + 3 = 63 sessions. You should always set the number of sessions to 50% greater than your maximum calculation as when Citect Clients are connecting and disconnecting the number of sessions will peak at a higher level.

The default value of this parameter was increased from 64 to 128 in Citect for Windows Version 3.0.