PORT 8081 / TCPDev & LocalhostExposure Risk: Low

Port 8081: React Native Metro / Nexus / Flink — React Native & Expo Metro JavaScript Bundler

Default bundler port for React Native (`npx react-native start`) and Sonatype Nexus Repository Manager.

Default Service

React Native Metro / Nexus / Flink

Process: node (metro)

Transport Protocol

TCP

IANA Registered Port 8081

Docker Port Flag

-p 8081:8081

Container to Host Mapping

How to Check & Kill Process on Port 8081 (EADDRINUSE Fix)

macOS & Linux (lsof / kill)

# Find process using port 8081
sudo lsof -i :8081

# Instantly kill process on port 8081
lsof -ti:8081 | xargs kill -9

Windows (PowerShell & CMD)

# Find PID listening on port 8081
netstat -ano | findstr :8081

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

Cross-Platform Node.js One-Liner

# Kill port 8081 via npx
npx kill-port 8081

# Or diagnose via Castov CLI
npx castov fix "EADDRINUSE :::8081"

Linux Firewall (UFW) & Connectivity Test

# Test if port 8081 is reachable
nc -zv localhost 8081

# Allow or deny port 8081 in UFW
sudo ufw allow 8081/tcp

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Frequently Asked Questions about Port 8081

What is Port 8081 used for?

Port 8081 is the standard network port for React Native Metro / Nexus / Flink (React Native & Expo Metro JavaScript Bundler) operating over TCP. The typical system daemon or process is node (metro).

How do I kill a process running on Port 8081 (EADDRINUSE)?

On macOS and Linux, run: lsof -ti:8081 | xargs kill -9 (or npx kill-port 8081). On Windows PowerShell/CMD, run: netstat -ano | findstr :8081 and then taskkill /PID <PID> /F.