If the client connected to your service appears to hang, the service may have asserted and displayed a message box that you are not able to see. You can confirm this by using Visual C++'s debugger to debug your code (see Using Task Manager earlier in this section).
If you determine that your service is displaying a message box that you cannot see, you may want to set the Allow Service to Interact with Desktop option before using the service again. This option is a startup parameter that permits any message boxes displayed by the service to appear on the desktop. To set this option, open the Services Control Panel application, select the service, click Startup, and then select the Allow Service to Interact with Desktop option.