Well, this is because your NIS booted with the default port. Now you're trying to connect to a different port but nothing's there. If you want to boot NIS with a port other than default, you have to change the config file @ path-to-nem/nis/config.properties. You'll find nem.httpPort = 7890 and nem.httpsPort = 7891 in that file. Change the values. Then restart NIS and do the same you tried earlier: change the port in your NCC according to what you just specified.

BUT you probably wanted to change the port of NCC, did you? head over to path-to-nem/ncc/config.properties, change nem.httpPort = 8989 and nem.httpsPort = 9090 to the port(s) you wish to use & reboot the NEM software.

OR to simply restrict outside access to port 8989, do as amytheplanarshift suggested above, block the port.

@ciappa: Entschuldige, falls das verwirrend wirkt. Wenn du lediglich nicht möchtest, dass jemand "von außen" dein NCC aufrufen kann, dann blockiere via Firewall den Port 8989 (der Port über den der Nem-Community-Client standardmäßig läuft).