How FTP works
What FTP is
Understand FTP as a stateful client-server protocol for navigating remote filesystems and transferring files.
8 minute lesson
FTP stands for File Transfer Protocol. It predates the Web and was designed for interactive file work between a client and server.
An FTP client can authenticate, change the remote working directory, list entries, download files, upload files, rename them, and remove them when permitted.
The protocol remains interesting because it exposes its operations as readable commands and numeric replies. It also carries historical design choices that do not fit modern firewalls easily.
FTP is stateful. The server remembers the authenticated user, remote working directory, transfer type, and next data endpoint across commands.
C: USER alice
S: 331 Password required
C: PASS ...
S: 230 Logged in
C: PWD
S: 257 "/uploads" is the current directoryCommands and replies stay on a control connection. Listings and file bytes use separate data connections. That split is the defining operational detail of FTP and the source of many firewall failures.
A successful command does not make classic FTP safe. Without TLS, credentials, filenames, commands, and file contents are visible and modifiable in transit.
Connect only to a server you own or are authorized to use. Follow one listing and one download in verbose client output. Mark the control replies and the separate data connection.
Lesson completed