Changing properties from within a hal callout

[Phillip Susi]

I have a hal callout bash script that does some configuration and needs 
to set some extra properties on the object it is invoked on.  I thought 
I could do this by running hal-set-property from inside the script, 
however, I have noticed that while the callout is executing, hal seems 
to be unable to accept connections as hal-set-property fails to connect. 
  I forked a pipeline in the background to sleep for a second or two, 
then call hal-set-property after the callout returns, and this seems to 
work most of the time, but causes a race condition.

What is the correct way to change properties from inside a callout, and 
isn't hal supposed to be listening for connections during callout execution?