PORT 20 / TCPSecurity & RemoteExposure Risk: High

Port 20: FTP Data — File Transfer Protocol (Data Channel)

Used by FTP servers to transfer file data between client and server. Unencrypted by default; prefer SFTP (Port 22).

Default Service

FTP Data

Process: vsftpd / proftpd

Transport Protocol

TCP

IANA Registered Port 20

Docker Port Flag

-p 20:20

Container to Host Mapping

How to Check & Kill Process on Port 20 (EADDRINUSE Fix)

macOS & Linux (lsof / kill)

# Find process using port 20
sudo lsof -i :20

# Instantly kill process on port 20
lsof -ti:20 | xargs kill -9

Windows (PowerShell & CMD)

# Find PID listening on port 20
netstat -ano | findstr :20

# Force kill by PID
taskkill /PID <PID_NUMBER> /F

Cross-Platform Node.js One-Liner

# Kill port 20 via npx
npx kill-port 20

# Or diagnose via Castov CLI
npx castov fix "EADDRINUSE :::20"

Linux Firewall (UFW) & Connectivity Test

# Test if port 20 is reachable
nc -zv localhost 20

# Allow or deny port 20 in UFW
sudo ufw allow 20/tcp

Frequently Asked Questions about Port 20

What is Port 20 used for?

Port 20 is the standard network port for FTP Data (File Transfer Protocol (Data Channel)) operating over TCP. The typical system daemon or process is vsftpd / proftpd.

How do I kill a process running on Port 20 (EADDRINUSE)?

On macOS and Linux, run: lsof -ti:20 | xargs kill -9 (or npx kill-port 20). On Windows PowerShell/CMD, run: netstat -ano | findstr :20 and then taskkill /PID <PID> /F.

Is it safe to expose Port 20 to the internet?

Port 20 has a High security risk profile. Used by FTP servers to transfer file data between client and server. Unencrypted by default; prefer SFTP (Port 22).