{"id":584,"date":"2026-09-09T16:56:57","date_gmt":"2026-09-09T16:56:57","guid":{"rendered":"https:\/\/www.vps.tc\/blog\/?p=584"},"modified":"2026-09-09T09:40:35","modified_gmt":"2026-09-09T09:40:35","slug":"what-is-ftp-file-transfer-protocol-explained","status":"publish","type":"post","link":"https:\/\/www.vps.tc\/blog\/en\/what-is-ftp-file-transfer-protocol-explained\/","title":{"rendered":"What Is FTP? File Transfer Protocol Explained"},"content":{"rendered":"
Table of Contents<\/strong><\/p>\n
    \n
  1. FTP still works, but it asks more from your firewall<\/a><\/li>\n
  2. What does FTP actually provide?<\/a><\/li>\n
  3. How an FTP connection works<\/a><\/li>\n
  4. Active and passive FTP are different firewall problems<\/a><\/li>\n
  5. FTP, FTPS, and SFTP are not interchangeable<\/a><\/li>\n
  6. Downloading and uploading files from the command line<\/a><\/li>\n
  7. Security checks I make before exposing FTP<\/a><\/li>\n
  8. Troubleshooting the errors I see most often<\/a><\/li>\n
  9. When FTP still makes sense<\/a><\/li>\n
  10. Frequently asked questions<\/a><\/li>\n
  11. Sources<\/a><\/li>\n<\/ol>\n<\/div>\n

    FTP still works, but it asks more from your firewall<\/h2>\n

    I usually meet FTP in the least convenient places: an old deployment workflow, a hosting panel, or a vendor integration that has been running unchanged for years. The login succeeds, then the directory listing hangs. That is when FTP’s two-connection design stops being an abstract protocol detail and becomes a real troubleshooting problem.<\/p>\n

    FTP stands for File Transfer Protocol<\/em>. It moves files between a client and a server, using one connection for commands and another for directory listings and file data. The standard control connection normally uses TCP port 21, while the data connection uses a separate port negotiated during the session.<\/p>\n

    Standard FTP can authenticate users, but it does not encrypt usernames, passwords, commands, or transferred files. That distinction matters before you create an account or open a port on a VPS.<\/p>\n

    What does FTP actually provide?<\/h2>\n

    FTP is a protocol, not a storage service. The FTP daemon and the operating system decide where files live, which users can access them, and how those accounts are restricted. FTP defines the conversation between the client and server; it does not decide the underlying disk layout or permissions.<\/p>\n

    That separation is easy to miss when a hosting panel presents everything as one form. You enter a hostname, username, password, and directory, but several independent pieces must work together: DNS, the control connection, the data connection, firewall rules, and filesystem permissions.<\/p>\n

    Small detail. It matters.<\/p>\n

    How an FTP connection works<\/h2>\n

    An FTP session may look like one connection in a graphical client, but the protocol normally uses two. The control connection carries commands. The data connection carries directory listings and file contents. This design is the reason FTP becomes awkward behind firewalls and NAT.<\/p>\n

    The control connection<\/h3>\n

    The client connects to TCP port 21 on the server. Usernames, passwords, directory changes, listing requests, and commands that start or finish a transfer travel through this channel. RFC 959 defines the core FTP commands and response behavior.<\/p>\n

    The server normally answers with three-digit response codes. For example, 220<\/code> means the service is ready, 230<\/code> indicates successful authentication, and 530<\/code> means the login failed. A graphical client may show only a vague error, but these codes become useful when I read the client or server log.<\/p>\n

    The data connection<\/h3>\n

    File contents and directory listings travel through a separate data connection. The way that connection is established depends on whether the client uses active or passive mode.<\/p>\n