It seems I can't open ports in my router (D-Link DIR-825). I have tried many different port numbers on both Port Forwarding and Virtual Server but the ports I open are closed according tohttp://www.yougetsignal.com/tools/open-ports/
For example I have opened port 8888 (both UDP and TCP, addressed to my local IP 192.168.0.107). This is my Apache port (configured with MAMP Pro) and I can access that port typing localhost:8888 in Google Chrome but not typing myexternalip:8888 when connected to another network (my iPhone's mobile network for example).
I have no software firewall or antivirus program installed (MacBook Pro, 2010, Yosemite) and I'm not behind a Carrier Grade NAT.