There is an infinite amount of service that can "run on port 8080". Or any port.
There is no enforcement that protocol x must use port a.
Your best bet would be to examine what that application gets sent back. If it is a standard protocol it should be easy to ferret out, Such as HTTP or FTP, even specific instances of those implementation may be discovered, ie Apache or IIS. If it is a custom protocol, that is not so easy, especially if the data is binary or the text returned doesn't explicitly say it. You can either stop and say it is a TCP or UDP application, or see if you can match the data to a proprietary protocol that has been reverse engineered.
Or if you have access to the machine, ask the OS.
"Computer science is no more about computers than astronomy is about telescopes" - Edsger Dijkstra