QIS can be instructed to exit automatically after the client disconnects from it without properly closing the QIS service.
If you don't do that, the QIS license will not check out and you will fail to start another service.

The command to instruct QIS to exit automatically should be defined at the beginning of a program (client) run.
Set_Time_Out\n
10\n

In this case, QIS will exit 10 seconds the client disconnects.

Note that if you have both NetTrace and your client program connected to QIS, NetTrace is also considered as a "client".  
So if NetTrace disconnects from QIS, QIS will exit after 10 seconds even if your client is still connected to QIS.


To disable this QIS auto exit, send 0 as the time out value.