How do FTP clients and servers work?

[jacatone]

I understand how P2P programs like Kazaa work, but I don't understand how FTP clients and servers work. Why do you need a NO-IP account with these programs? Thanks.

[reboot]

You don't need a no-ip account.
An FTP server is just a computer with an FTP program, that accepts a certain number of connections on certain ports.
A client is a program you would use to connect to that server.
For those that have a dynamic IP, or wish to keep their REAL IP anonymous, get a no-ip account.

[jacatone]

A FTP client is used to connect to that server? I'm confused. Wouldn't I use the client to connect to other FTP servers? I'm assuming that with these programs you can only trade files when both parties are online and have their programs running?

[reboot]

A "client" is simply a program. In this case, it's used to access a server (FTP) so it's called a client. Just like your email program is a client, accessing the mail server.
Any client can access any number of FTP servers, they're all over, just like websites, though not as many. It's just a different way of downloading stuff.
If I am running an FTP server, I can give you the necessary info (usually the ftp name or IP, a username, and password) to access my FTP. There are quite a few anonymous FTP sites too, that will let anyone login.
If you download the trial of CuteFTP, it has a bunch of servers you can connect to for free.
If you have a friend running an FTP server, you could log in to it and download, using a client.
I often have files much larger than 5 meg (the common maximum filesize that your ISP and most free web hosts allow), so I set up an FTP, and then give my friends the info, and they can log in and download the stuff they want.
Don't confuse P2P filesharing with FTP, it works differently, and yes, you'd both have to be online, one of you running a server, to upload/download from eachother.

[jacatone]

Thanks for clarifying that for me. Apparently there are other ways to file share privately. There's a program called, www.fileshare.com that allows just one on one sharing. Also IM programs like ICQ have that capability.

[reboot]

Most of the IM programs allow some sort of filesharing. There's also IRC, Telnet, etc.
Each has a specific set of protocalls, and each can be rather specialized.
Depending on exactly what you want to do, and the hardware and software you have, determines the easiest way to share information.