Is x server connection still valid?

[hugo vanwoerkom]

Hi,

I hope this is the right place to ask this question:

I have various displays and want to modify the LEDs of the keyboards
connected to them.

In order to do that I XOpenDisplay and see if it is successful.

If successful I use XChangeKeyboardControl.

But how do I find out next time I use that function that the X server
connection is still valid?
The user may have logged off, causing a SIGPIPE fault in using the function.
Is there some way to find if the display structure actually still is
for an existing connection without getting into that SIGPIPE?

Thanks

Hugo