portmon

Cross-platform CLI to list listening ports, see which process owns them, and kill processes by port or PID.

Works on Windows, macOS, and Linux.

Install

npm install -g portmon

Or run without installing:

npx portmon list

Quick start

# List all listening TCP ports
portmon

# Who is using port 3000?
portmon find 3000

# Kill the process on that port
portmon kill 3000 -y

# Interactive live view
portmon watch

Commands

list (default)

List listening ports.

portmon
portmon list
portmon ls
portmon list --udp      # include UDP
portmon list --json     # JSON output

find / who

Show which process is listening on a port.

portmon find 3000
portmon who 5173
portmon find 3000 5173   # check multiple ports
portmon find 3000 --json

kill

Kill the process listening on a port.

portmon kill 3000       # prompts for confirmation
portmon kill 3000 -y    # skip confirmation
portmon kill 3000 -f -y # force kill

kill-pid

Kill a process by PID.

portmon kill-pid 12345
portmon kill-pid 12345 -f -y

watch / w

Interactive live view of listening ports.

portmon watch
portmon watch -i 1000   # refresh every 1 second
portmon watch --udp

| Key | Action | |-----|--------| | ↑ / ↓ | Move selection | | j | Move down | | Enter / d / k | Kill selected process | | f / K | Force-kill selected process | | r | Refresh now | | q / Ctrl+C | Quit |

The list auto-refreshes (default every 2s). Selection stays on the same port and PID across refreshes when possible.

Requires an interactive terminal (TTY).

Example output

┌──────┬───────┬──────────┬──────────┬───────────┐
│ PORT │ PID   │ PROCESS  │ PROTOCOL │ ADDRESS   │
├──────┼───────┼──────────┼──────────┼───────────┤
│ 3000 │ 14204 │ node.exe │ TCP      │ 0.0.0.0   │
│ 5173 │ 9188  │ node.exe │ TCP      │ 127.0.0.1 │
└──────┴───────┴──────────┴──────────┴───────────┘

2 listening port(s)

How it works

| OS | Discovery | Kill | |----|-----------|------| | Windows | netstat -ano + tasklist | taskkill | | macOS | lsof | SIGTERM / SIGKILL | | Linux | lsof (fallback: ss) | SIGTERM / SIGKILL |

No native addons — only Node.js and standard OS tools.

Requirements

• Node.js 18 or later
• On macOS/Linux, lsof is recommended (ss is used as a Linux fallback)

Permissions

Killing system services or processes owned by another user may require an elevated shell (Administrator on Windows, sudo on Unix). Clear errors are shown when a kill is denied.

Development

git clone https://github.com/alaminrifat/portmon.git
cd portmon
npm install
npm run dev -- list
npm run build
node dist/cli.js list

See CONTRIBUTING.md for setup details, guidelines, how to submit pull requests, and how maintainers release new versions to npm.

License

MIT