Port stays "ESTABLISHED" on app exit

Question

Good morning, I am working with a remoting application which communicates with a central server. Without getting in to the specifics of the application, I am hoping someone can give me an idea of where to go with this. The problem is basically this. When the application connects to the server, it establishes a connection on port 8090. Upon closing the application, the port should get closed out. This is not happening and I was hoping that someone may be able point me in the right direction. In general, should the port automatically close upon closing the app? Does something need to be added to the disposing section of the app? Does this totally depend on the application / should it contain code to close the socket on exit? Any information would be extremely helpful. Thanks all.