System Event message queue

[Tripredacus]

I am encountering a problem where a program of mine needs to notify another software program, but it cannot. Here is the dillema.

I have an application that is pushed with a deployment solution over a network. The server sends a command to its client handler to execute the program. The program executes (presumably) but after about 15 minutes the server reports back that the execution failed with a return code of 1. The return code of 1 is sent back from the client because it has timed out waiting for a response from my program that indicates it has completed executing.

The client is monitoring the SYSTEM message queue for the exit code sent by my program. The problem is that my program doesn't send its exit code to System. Now I am aware that Windows Installer can send an exit code to System when it completes running an MSI. I have currently set up my program to only send an exit code of 0 and an additional program that sends a 1. I am awaiting a response to see if either exit code is detected by Windows.

What should I be looking for in order to research how to send an exit code to system?

What is the common name of that queue?

Are there any documentation on how Windows Installer sends exit codes to Windows?

Note that this implementation is not aimed at writing to the Event Log, as that is not something monitored by the client.