PORT 443 / TCP/UDPWeb & HTTPExposure Risk: Low

Port 443: HTTPS — HTTP Secure over TLS/SSL & HTTP/3 (QUIC)

Standard port for all encrypted web traffic, REST APIs, GraphQL endpoints, and WebSockets (wss://). HTTP/3 uses UDP on port 443.

Default Service

HTTPS

Process: nginx / caddy / traefik

Transport Protocol

TCP/UDP

IANA Registered Port 443

Docker Port Flag

-p 443:443

Container to Host Mapping

How to Check & Kill Process on Port 443 (EADDRINUSE Fix)

macOS & Linux (lsof / kill)

# Find process using port 443
sudo lsof -i :443

# Instantly kill process on port 443
lsof -ti:443 | xargs kill -9

Windows (PowerShell & CMD)

# Find PID listening on port 443
netstat -ano | findstr :443

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

Cross-Platform Node.js One-Liner

# Kill port 443 via npx
npx kill-port 443

# Or diagnose via Castov CLI
npx castov fix "EADDRINUSE :::443"

Linux Firewall (UFW) & Connectivity Test

# Test if port 443 is reachable
nc -zv localhost 443

# Allow or deny port 443 in UFW
sudo ufw allow 443/tcp

Frequently Asked Questions about Port 443

What is Port 443 used for?

Port 443 is the standard network port for HTTPS (HTTP Secure over TLS/SSL & HTTP/3 (QUIC)) operating over TCP/UDP. The typical system daemon or process is nginx / caddy / traefik.

How do I kill a process running on Port 443 (EADDRINUSE)?

On macOS and Linux, run: lsof -ti:443 | xargs kill -9 (or npx kill-port 443). On Windows PowerShell/CMD, run: netstat -ano | findstr :443 and then taskkill /PID <PID> /F.

Is it safe to expose Port 443 to the internet?

Port 443 has a Low security risk profile. Standard port for all encrypted web traffic, REST APIs, GraphQL endpoints, and WebSockets (wss://). HTTP/3 uses UDP on port 443.