Applies To:
  • CitectSCADA 4.xx, 5.xx

Citect may deadlock or hang if you are using any TCPIP based protocol on a dual processor computer. 

This problem is caused by a bug in the Microsoft WINSOCK layer. You must get a hotfix Q171181 from Microsoft (Microsoft hotfix will be shipped with Windows NT 4.0 Service Pack 4 and Windows NT 5.0). You must also install a modified Citect TCP/IP driver which works with the Microsoft hotfix change. This TCP/IP driver will be shipped with version 5.01 or available on the FTP site. The new TCP/IP driver has an enhancement so that is it sees the WSAENOBUFS error, then it will sleep for a period and retry. This is controlled by the following parameter:


Where value >= 0. default: 0.

The work around is disabled when NoBufferSleepTime is set to zero.

Side effect. Citect will be blocked for NoBufferSleepTime milliseconds when WSAENOBUFS error occurs.