My Computer Science teacher just got me confused.

In FTP, you connect to port 21 and login and then a command link is opened and it is kept open.
Commands are sent through the command link and when you transfer files, a data link is opened and the file is transfered through that link.

I want to know if what I just said was right.

Are these command links and data links actually other free ports on the Server and Client.

And does the same thing apply to HTTP.

Can anyone please explain exactly how a file download happens in HTTP?

Thanks in advance,
Denesh.

In response to your signature:

I can guarentee you he writes some really tight code.



Come on....He's God!

Yes, FTP (control) connections are made on port 21, but data transfer happens on port 20, in passive mode, or some random high port, depending on the particular ftp server, in active mode.

and during http session you are still connected to port 80 on the server with a hiher port on your client, as soon as you start downloading you are opening up another http session, your browser configured such way so it either launches a downloader or opens up a file if there is a derective that tells the browser to open such file with a helper application rather than save it to your harddrive.

I want to know how the webserver sends the file.

Does it sends through its port 80 or does it open another port and send it through that??

And about the signature, Just think about it. When writing a game, you are creating your own world, where you are god. Think about the one who made the world we are in. He actually made us think about him !!!