FTP Explained: How It Works and What to Look For
FTP transfers files using separate control and data connections.
Published by Protocol Explorer · Reviewed
How FTP works
Commands and replies travel on a control connection. A separate data connection carries a file or directory listing, with active and passive modes establishing it differently.
What to look for in an exchange
Track the control commands and the separate data path. Plain FTP does not provide transport encryption; FTP over TLS is a separate extension.
Follow an example step by step
- Follow the control connection and read the server replies to login and transfer commands.
- Determine whether the session uses active or passive data connection setup.
- Associate the separate data connection with the relevant file or directory transfer.
Common interpretation mistake
FTP control and data use separate connections, which can complicate firewall and NAT handling.
Key point to remember
Plain FTP does not encrypt passwords or file contents; FTPS is a separate TLS-based extension.
Explore the protocol
The FTP overview is free without an account. Its full interactive lesson is included in Protocol Explorer Pro, a one-time $4.99 purchase; an account is required to buy Pro and restore the licence across devices.
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Specification
Read the primary specification for FTP for the authoritative protocol details. The interactive scenario is a simplified teaching model, not a capture of your network.
Continue learning
How to read a packet · TCP · UDP · HTTPS