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FSUIPC Error #65540:


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Hi Paul,

I have a serious issue which I could not solve in hours of troubleshooting. The problem occured after some code changes in my application. I get the following exception with FSUIPCConnection.Process:


FSUIPC Error #65540: FSUIPC_WRITE_OFFSET_NEVER_READ. An attempt was made to write a value to an offset that has never been read. Offsets must be read at least once so thier values are in sync with the Flight Sim. If this offset is only ever writen to, mar...


Well, I do understand what the message tells me, but 'Im not able to identifier the problem. Can you give me some more information regarding the background of the message which might help me to find the problem.


I use FSUIPC client DLL version: 3.0.5898.3




Kind regards,



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Hi Ruediger,


The DLL decides whether to read or write an offset based on the value. If the current value is different than the previous value that was read, the DLL writes the new value.


This error is generated when the DLL detects a change, but, that offset has never had a value read.


I think this is the first time you are calling Process(), but before that you have set the value of some offsets.


Make sure your first process() call is before you've changed any values. Maybe do this right after you call FSUIPCConnection.Open().


If you have offsets that you only want to write to, mark them as write-only.


If you can't track it down I can give you a modified DLL that will tell you which offset is causing the problem. Just let me know what Framework version you want it built against. (2.0, 4.0, 4.5 etc).



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Hi Paul,

many thanks for your help. The key was to insert a FSUIPCConnection.Process after the generation of some dynamic offsets with startup of the application. I can not explain why this suddenly became a problem, because I did not touch that part of the program for a year or more. However, problem seems to be solved, that the importend point.



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