Looking for locally run port scanner

I'm trying to find a port scanner I can run locally against itself.

Software vendor says a port is being blocked. Firewall is OFF, everything is OFF and its running via localhost where there is no blocking.

Yet they insist it is being blocked. The problem is, they have no idea what port it uses, randomly picks a port between 1024 and 65xxx.

So I need to scan every single TCP port from 1024 to the top end and see if any are being blocked outbound.

I tried Superscan but that does not do what I'm looking for.

Thanks