Applies To:
  • CitectSCADA 4.10 4.20

I have upgraded to Citect V4.10 from V3.30 and the communication functions that used to work in V3 are no longer working. Usually the functions containing the Communications functions will work once but after this it fails. What is causing this problem? 

In Citect V4.10 the ComClose() function has a side affect that causes a problem with the ComWrite() function the next time it is run. The return value for ComWrite() will return an error code instead of 0 even if the write is successful. This problem can be worked around by not doing any error checking on the return value for the ComWrite(). You may also get a fix for this problem by down loading the latest COMX.DLL (4/11/96 or later) from the BBS or FTP site which contains the fixes for this problem.