Applies To:
  • CitectSCADA 5.xx, 6.xx, 7.00
  • CitectHMI 5.xx, 6.xx, 7.00

A client/server connection is not re-established after a network failure when using NetBIOS over TCP/IP on Windows 2000/XP machines.

This will occur if the network cable is unplugged from a machine being used as a display client or as a server and configured to use Discovery as the primary networking model. The components’ network connections will be broken and will not be re-established once the network cable is plugged in again. If the display client is scanning the I/O Server, it will display #COM due to the broken connection. In this instance, the CitectSCADA components must be restarted in order to re-establish network communications.

This situation is reported to the syslog with the message, "NetBIOS: Invalid adapter number error. Disable Win2000 Media sensing".


This problem is due to the Windows Media Sense feature which was introduced in Windows 2000. To correct this problem, disable Media Sense in the following manner:

1. From the start menu select Run, and open Regedt32.exe.

2. Use the Registry Editor to view the following key in the registry:


Add the following registry value:

Value Name: DisableDHCPMediaSense
Data Type: REG_DWORD -Boolean
Value: 1

3. Restart the computer.

Media Sense support provides a mechanism for the network adapter to notify the protocol stack of media connect and media disconnect events. Whenever Windows detects a "down" state, it removes the bound protocols from that adapter until it is detected as "up" again. This allows computers to connect to networks with different DHCP options without the need to release and renew the IP configuration by using ipconfig.exe. Disabling Media Sense may change the behaviour of other applications on the computer.

This issue has been resolved for version 7.00.  CitectSCADA components will be able to re-establish their network connections after a network failure even if Windows Media Sense is enabled.

Note: This article supersedes the information in Q3415, Q3373 and Q3430.


netbios cable pull dropped reconnected