What Is FTP? A Simple Guide to File Transfer Protocol

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Arjit Sharma
02 Mins

Ever needed to upload a file to a server or download a large file from one? That’s where FTP (File Transfer Protocol) ****comes in. It is one of the oldest yet still widely used methods for transferring files over the Internet.

What Is FTP?

FTP (File Transfer Protocol) is a standard protocol used to transfer files between a client and a server over a network.

  • The client initiates the connection and requests uploads/downloads.
  • The server provides access to a file system where files can be stored or retrieved.

How FTP Works

FTP uses two separate TCP connections -

  1. Control Connection (Port 21) - Used for sending commands and receiving responses (e.g., USER, PASS, RETR, STOR). It remains open throughout the session.
  2. Data Connection (Port 20 or dynamically assigned) - Used for actual file transfer. It is opened and closed for each file sent/received.

FTP Modes: Active vs Passive

Active Mode

  • The client opens a port and waits for the server to establish the data connection.
  • This can cause issues if the client is behind a firewall or NAT, as incoming connections may be blocked.

Passive Mode (PASV)

  • The server opens a port, and the client initiates both connections.
  • More compatible with firewalls and NAT setups — making it the default mode for most clients today.

Is FTP Secure?

Classic FTP is not secure, it sends everything in plain text*(including your username, password, and file contents)*. To solve this, developers now prefer secure alternatives that feel familiar to FTP but offer encryption built-in -

FTPS (FTP Secure) - Adds SSL/TLS encryption to traditional FTP and is ideal when working with legacy systems or hosting providers that still support FTP.

SFTP (SSH File Transfer Protocol) - It is built on top of SSH protocol, using port 22. It allows file transfers, directory traversal, permission management, and more - all over a secure connection.

SSH for Developers

SSH (Secure Shell) is your Swiss Army knife for remote development. It’s not just for logging into servers - it’s a gateway to automation, deployment, and secure file handling.

Common Developer Use Cases

  • Remote access:ssh user@server.com log into a remote machine securely.
  • Securely transferring the file.
  • Access remote web server locally or expose your local dev server remotely.
  • Connect to a remote DB securely without exposing it to the internet.
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