In such cases you have a direct connection to the Internet.

You will use either one depending on whether your PC is behind a firewall.Īctive mode is usually used when there isn't any firewall between you and the FTP server. Please click here to view the full picture.įTP has two separate modes of operation: Active and Passive. Only Port 21 was used ! Here is the screen shot: Now, in the next picture I ftp'ed into my NetWare server here at home and guess what. Please click here to view the full picture I have included a screenshot from my workstation which clearly shows the 2 ports used. The best thing you can do to 'see' it yourself is to grab a packet sniffer which you will conveniently find in our download section and try to capture a few packets while you're ftp'ing to a site. Port 21 is used to establish the connection between the 2 computers (or hosts) and port 20 to transfer data (via the Data channel).īut there are some instances where port 21 is used for both, establishing a connection and data transfer and I will analyse them shortly. Now, we mentioned that FTP uses TCP as a transport, but we didn't say which ports it uses! Port numbers 21 and 20 are used for FTP. As I have noted in other sections, it's important to understand the concept of the OSI model, because it will greatly help you understand all this too :) The picture below shows where FTP stands in contrast to the OSI model.

Chances are if you download files, you've probably used ftp a few hundred times without realising it ! And if you have a huge warez collection, then make that a couple of thousand times :) This means that FTP inherits TCP's robustness and is very reliable for transferring files. Most recent specifications of the protocol are listed in RFC 959.::/wysiwyg_introtext::įTP uses TCP as a transport protocol. Various standard file transfer protocols existed even before the Internet was available to everyone and it was these early versions of the file transfer software that helped create today's standard known as the File Transfer Protocol (FTP). File transfer is among the most frequently used TCP/IP applications and it accounts for a lot of the network traffic on the Internet.

Whats my filezilla port