A Little Help with Port Forwarding

Hi folks!

I am new to hacking, I recently learned to hack android over LAN but it isn't working over WAN. My modem is AN1020-25, when I go to admin panel and NAT -- Virtual Servers Setup, I add port 4444 TCP/UDP with my current local dynamic IP, but then I go to canyouseeme.org to check port 4444 and it says connection refused. I go to terminal and type "nc -l -p 4444" and it works only for a few minutes and then again canyouseeme.org says connection refused. How to open this port permanently and what am I doing wrong. Heres a screen shot of the NAT Virtual Server setup, and sorry for my bad English -