The client connects from a random port to port 21 on the server and issues the PASV command. Here is a short explanation of how this mode works: Once the FTP server replies, it indicates what port number it has opened for the data transfer. Passive mode works in a similar manner to the Active mode, however instead of sending the PORT command, it sends the PASV command, which is a request for a server port to connect to for data transmission. ( obviously all firewalls will block a remote connection request like this!) Once connection is established, file transfers are then made through these client and server ports. The server connects from port 20 to the client port designated for the data channel. It sends the PORT command, specifying what client-side port the server should connect to, that will be used for the data channel. The client connects from a random port of the file transfer client to port 21 on the server. Next, I will provide a simplified explanation how this mode works: Active mode FTPĪctive mode is the older version of the two modes.
Although FTP can be secured with SSL/TLS to ensure secure transmission, encrypting the content, username and password, external users prefer SFTP (Secure File Transfer Protocol) also known as SSH File Transfer Protocol against FTP, probably because it runs over a single port and it's secure without requiring further configurations and certificates.įTP can run in two modes and those are Active and Passive mode. That being said, FTP is mostly used for data exchange inside your company’s private network. Furthermore, firewalls and load balancers didn’t exist. The inventor didn’t build the protocol with security in mind as mainframes were more common and attacks to information security were not widespread back in the 80’s.
Any data sent over these channels can be exploited with a MITM (Man-in-the-middle) attack using ARP poisoning and packet sniffers. One of the reasons FTP has lasted so long is that it has so many clients available on every platform you can think of.įTP runs over two separate channels known as the command channel and the data channel, which both are unencrypted.
#FILE SERVER SPECS 40 USERS PDC FILE STORAGE PRINT SERVER HOW TO#
Open standards are awesome, and the File Transfer Protocol FTP (inspite of its flaws) has been in constant use for an amazing 40 years! FTP can be a pain to run over firewalls and load balancers, so this blog explains how to configure Microsoft FTP and HAProxy.įTP (RFC 114!) was first implemented at MIT more than 40 years ago, and to this day this is still the standard protocol for file transfers.
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