Trace a listening port to a running process.md

title	Trace a Listening Port to an Application
tags	linux networking troubleshooting how-to
aliases	Port to Process Mapping
created	2026-07-03

Trace a Listening Port to an Application

Using ss (modern, recommended)

# Show all listening TCP/UDP ports with process info
ss -tulpn

# For a specific port
ss -tulpn | grep :8080

Using netstat (legacy)

# Show listening ports with PID/Program name
sudo netstat -tulpn

# For specific port
sudo netstat -tulpn | grep :8080

Using lsof

# Show process using a specific port
sudo lsof -i :8080

# Show all internet connections
sudo lsof -i

Using fuser

# Identify process using a port
fuser 8080/tcp

Example Output Interpretation

tcp   LISTEN  0  128  0.0.0.0:8080  0.0.0.0:*  users:(("nginx",pid=1234,fd=6))

• tcp/udp: Protocol
• LISTEN: State (listening for connections)
• 0.0.0.0:8080: Binding address and port
• nginx: Process name
• pid=1234: Process ID
• fd=6: File descriptor

Quick One-Liners

# Find what's on port 8080 (any tool available)
sudo ss -tulpn | grep :8080 || sudo netstat -tulpn | grep :8080 || sudo lsof -i :8080

# Kill process on port
sudo kill -9 $(sudo lsof -t -i :8080)