FTP

✅ What is FTP?

FTP (File Transfer Protocol) is a standard network protocol used to transfer files between a client and a server on a computer network. It allows users to upload, download, rename, delete, and manage files on remote servers.

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🔑 Key Characteristics of FTP:

Feature	Description
Protocol Type	Application Layer Protocol (OSI Layer 7)
Connection Type	Connection-oriented (uses TCP)
Ports Used	Port 21 (Control), Port 20 (Data)
Transfer Type	Plaintext (default, not encrypted)
Secure Version	FTPS (FTP Secure via SSL/TLS), SFTP (over SSH)
Data Transfer	Upload and download files, manage directories

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⚙️ How FTP Works (Basic Flow):

1. Establish Connection:

• FTP client connects to FTP server via control connection (Port 21).

• User provides login credentials (username, password) — unless anonymous login is allowed.

2. Command & Response:

• Client sends FTP commands (e.g., LIST, GET, PUT).

• Server responds with status codes and messages.

3. File Transfer:

• Data connection (Port 20 or other negotiated port) is used to transfer files.

4. Disconnect:

• After file operations, client disconnects from the server.

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🔁 FTP Modes of Data Transfer:

Mode	Description
Active	Client opens a port and listens, server connects to client to send data.
Passive	Server opens a port and listens, client connects to server for data (more firewall-friendly).

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📡 Common FTP Commands:

Command	Description
USER	Provide username.
PASS	Provide password.
LIST	List directory contents.
RETR	Retrieve (download) a file.
STOR	Store (upload) a file.
DELE	Delete a file.
MKD	Make a directory.
RMD	Remove a directory.
PWD	Print working directory.
CWD	Change working directory.
QUIT	Close connection.

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🔐 Secure Alternatives to FTP:

Protocol	Description	Port
FTPS	FTP over SSL/TLS (encrypted)	21 (control), other for data
SFTP	SSH File Transfer Protocol (completely different, but secure)	22

💡 Note: SFTP is not FTP with SSH. It's a separate protocol that runs over SSH.

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📊 Common FTP Status Codes:

Code	Meaning
200	Command OK
220	Service ready for new user
221	Closing control connection
331	Username OK, need password
425	Can't open data connection
530	Not logged in (login incorrect)
550	File not available (e.g., not found, no access)

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⚙️ Example of FTP Session:

vbnetCopyEditClient: 220 Welcome to FTP server
Server: USER john
Client: 331 Password required
Server: PASS secret123
Client: 230 Login successful
Server: LIST
Client: 150 Here comes the directory listing
Client: 226 Directory send OK
Server: QUIT
Client: 221 Goodbye

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📥 Popular FTP Clients:

Client Name	Platform	Notes
FileZilla	Windows, Mac, Linux	Free, open-source, user-friendly
WinSCP	Windows	Great for SFTP, SCP, FTP
Cyberduck	Mac, Windows	FTP, SFTP, WebDAV, cloud storage
Transmit	Mac	Premium, popular for Mac users

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🌍 Common Use Cases of FTP:

• Uploading websites to web hosting servers.

• Sharing large files over the Internet.

• Automated file transfers in businesses (via scripts).

• Backup data to remote servers.

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⚠️ FTP vs. SFTP (Comparison Table):

Feature	FTP	SFTP
Port	21 (control), 20 (data)	22
Encryption	❌ No (plain text)	✅ Yes (via SSH)
Authentication	Username/Password	Username/Password or Key-based
Firewall-friendly	❌ Complex with active mode	✅ Simple, single connection
Secure?	❌ No	✅ Yes

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✅ Summary of FTP:

Feature	Description
Protocol	File Transfer Protocol
Port	21 (Control), 20 (Data)
Purpose	Transfer files between client and server
Secure Version	FTPS, SFTP
Commands	USER, PASS, LIST, RETR, STOR, QUIT
Transfer Modes	Active, Passive
Common Clients	FileZilla, WinSCP, Cyberduck