|I just want to add something.|
IF I want to put other application that can access by public in internet in this computer.Is it possible ??
The answer is yes, it not only is possible, but it is the ONLY way you can access.
You have a router. The router's external interface will have the public IP address. Because you are most likely (if you're smart) using a private subnet internally you have to do what Stuart said.....which is create a port forward.
So, let's pick a public IP out of thin air to use for an example. Let's say your router's external interface has been assigned the following IP by your provider
IP = 184.108.40.206
Now let's say you're using the following private subnet internally: 192.168.0.0/24
Let's say you've installed your ftp server on a computer with the following IP address: 192.168.0.200
On your router, you would create a port forward that looks as follows:
Send port 21 to 192.168.0.200
To connect to your ftp server from any other place in the world (using the internet of course) you would do the following:
The ftp request would hit the router on port 21. The router would look at the forward and say to itself, "Oh, I have to send this to 192.168.0.200" and it would do so and you would connect to the ftp server.
Does that make sense now?
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.