"My router has DMZ enabled" - This statement concerns me. I've tinkered with a LOT of different SOHO routers over the years (and currently work on a large enterprise network). EVERY single one I can remember, you don't simply enable DMZ... you specify the IP address of the DMZ host.
This is the most disturbing part: "Im trying to open 55550-55560" Those are part of the range of ephemeral ports. These are mostly used for outbound connections by your OS.
PLEASE tell us what application you are trying to make work, and what exactly is not happening, which you expected to happen. Are you trying to make a game server?? Are you trying to make your server available over the Internet??? What kind of server is it??? (File, Print, FTP, TELNET, RDP, VNC, etc......).