I can not access my Xammp server from internet.

[ian11]

I am new to linux and web servers. I have installed Damn Small Linux and Xampp. I am using a guide in the book " The Official Damn Small Linux Book" and I have gotton to the point where Xampp is up and running. I Just set up my firewall and have given permissions "80 and 21". Now I am trying to connect to my server from another computer through the internet for the 1st time. I was able to obtain my external IP addr. and I entered it into the address bar of the other computer on a different internet connection and it did not go to my server. Can anyone tell me what I am doing wrong or tell me the correct way to link to my server from the internet. Do I have to get a static IP address? When I go to http://localhost on the linux machine, it says all is working.........Please help! Thnx,
Ian11