Labview eating up CPU time

Question

I am running a program (LV 7.1) which has several VIs running concurrently.  It is a self-made server-client architecture utilizing TCP/IP communication protocol.  When the program is running with all of the VIs executing simultaneously and the client sending TCP/IP requests to the server, my whole computer starts to freeze (CPU usage shows 100%) and the TCP/IP communication times out.  The program was running fine when I made some simple changes and then it started to behave as above.  I went back to previous versions of the program and they are now acting the same way.  I can load the program on another machine and it runs fine.  I reloaded Labveiw 7.1, no change.  I am running Windows XP Professional, version 2002 with service pack 2.  I have a Xeon 3.6 GHz CPU with 3 GB RAM.  I tried the program on several other far less powerful machines and it works fine.  Any suggestions would be appreciated.

Answer 1

I would start by placing a delay (as others suggested) in your client VI. Place a probe on the error out of the TCP Open in the client VI and check for errors there. Look for error code 60.
It sounds as if your are opening and closing ports quickly. There are a finite number concurrent TCP/IP ports available from the OS. If they are not closed properly, they will need to time out before the OS closes it. Your CPU load may be pegging becuase you are flooding the TCP stack with open connection requests and you've max'd out the connections.
If the error is indeed 60, then you should handle that gracefully in your client (maybe a dialog box with a message 'sever not accepting connections; retry or abort'). If your design includes frequent TCP open and close ( > 1 per second) you may want to consider opening a more persistent connection; store the Connection ID in a shift register or a functional global and only close it when you are done communcating with the server.
See this post: http://forums.ni.com/ni/board/message?board.id=170&message.id=240177&query.id=349798#M240177
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