System.Net.HttpListenerException (0x80004005): Failed to listen on prefix XXXX because it conflicts with an existing registration on the machine
Article Number: 000035393 | Last Modified: 2019/01/17
Description
Under some circumstances, you can receive by upgrading a QVSource or QVWebConnector component the message
System.Net.HttpListenerException (0x80004005): Failed to listen on prefix XXXX because it conflicts with an existing registration on the machine
By looking at the startup log its reflected like this in there:
Failed to listen on prefix 'http://XXXXXXX:YYYY/' because it conflicts with an existing registration on the machine.
Resolution
This is because QVSource, or another application has already reserved this endpoint.
A typical specific entry might read:
System.Net.HttpListenerException (0x80004005): Failed to listen on prefix 'https://+:5555/' because it conflicts with an existing registration on the machine.
After you have been running QVSource with remote access enabled but then attempted to move to running QVSource over SSL.
There are a couple of solutions to this.
Firstly, try running a PowerShell Command prompt as administrator and entering:
netsh http show urlacl | where {$_ -match ':5555'}
Note we have entered the port number (which would have been the YYYY value in the above error message).
It is likely you will see something like the following:

Indicating that an application (which might be QVSource) has already reserved this endpoint.
You can also enter netsh http show urlacl which will list all reservations on the machine with additional information about each but you will have to manually find the ones matching the port number you are using.
If this is the case, or you know that you are safe to remove this reservation, you can simply run the following command to delete the URL reservation:
netsh http delete urlacl url=http://+:5555/
NOTE: The value after url= must exactly match that shown from the result(s) of running netsh http show urlacl above.
Which should confirm the deletion:

You should now find you can start QVSource.