Sonar is a command-line tool that shows everything listening on localhost ports, including Docker containers and dev servers, with options to kill processes, view logs, and inspect services.

How do I kill a process on a specific port?

Run 'sonar kill 3000' for SIGTERM or 'sonar kill 3000 -f' for SIGKILL. For Docker containers, it runs 'docker stop' automatically.

Can Sonar show resource usage?

Yes. Use 'sonar list --stats' to see CPU, memory, threads, uptime, and state for each process or container.

Does Sonar work on Linux?

Yes. Sonar supports macOS (uses lsof) and Linux (uses ss).

What is the Sonar tray app?

A native macOS menu bar app that shows live port stats. Included in the install script or buildable separately with Swift.

Can Sonar wait for a port to be ready?

Yes. Use 'sonar wait 5432 --timeout 30s' to block until a port accepts connections. Add '--http' to wait for HTTP 200 instead of just TCP open.

Sonar: Finally Know What's Running on Your Localhost Ports

Q: How do I install Sonar?

Run: curl -sfL https://raw.githubusercontent.com/raskrebs/sonar/main/install.sh | bash. Or use Go: go install github.com/raskrebs/sonar@latest

Q: Does Sonar work with Docker?

Yes. Sonar shows container names, Compose project names, images, and container ports. Docker containers are stopped with 'docker stop' instead of signals.

By Prahlad Menon Published 2026-03-23 3 min read

TL;DR: Sonar is a CLI that shows everything listening on localhost—ports, processes, Docker containers—and lets you kill, inspect, or tail logs with simple commands. No more lsof | grep gymnastics. Install: curl -sfL https://raw.githubusercontent.com/raskrebs/sonar/main/install.sh | bash

Every developer has memorized their port numbers. 3000 is Next.js. 5432 is Postgres. 8080 is the API. And then one day you run npm run dev and get “port already in use”—and now you’re spelunking through lsof -iTCP -sTCP:LISTEN | grep ... trying to figure out if it’s a zombie Docker container or an orphaned dev server from a branch you forgot to close.

Sonar fixes this. One command shows everything. One command kills it.

What Does Sonar Do?

Sonar shows all services listening on localhost ports in a clean table format:

$ sonar list
PORT  PROCESS              CONTAINER           IMAGE              URL
1780  proxy                my-app-proxy-1      traefik:3.0        http://localhost:1780
3000  next-server                                                 http://localhost:3000
5432  db                   my-app-db-1         postgres:17        http://localhost:5432
6873  frontend             my-app-frontend-1   frontend:latest    http://localhost:6873
9700  backend              my-app-backend-1    backend:latest     http://localhost:9700

5 ports (4 docker, 1 user)

It knows the difference between Docker containers and native processes. It shows Compose project names. It gives you clickable URLs.

How Do I Install Sonar?

One-liner install:

curl -sfL https://raw.githubusercontent.com/raskrebs/sonar/main/install.sh | bash

This downloads the binary to ~/.local/bin. Restart your terminal or source ~/.zshrc.

If you prefer Go:

go install github.com/raskrebs/sonar@latest

Shell completions (tab-complete port numbers):

sonar completion zsh > "${fpath[1]}/_sonar"   # zsh
sonar completion bash > /etc/bash_completion.d/sonar  # bash
sonar completion fish | source                # fish

How Do I Kill a Process on a Port?

sonar kill 3000        # SIGTERM
sonar kill 3000 -f     # SIGKILL (force)

For Docker containers, Sonar automatically uses docker stop instead of sending signals.

Kill multiple at once:

sonar kill-all --filter docker          # stop all Docker containers
sonar kill-all --project my-app         # stop a Compose project
sonar kill-all --filter user -y         # kill all user processes, skip confirmation

What Features Does Sonar Offer?

Inspect a port:

sonar info 3000

Shows full command, user, bind address, CPU/memory/threads, uptime, health check result, and Docker details.

View logs:

sonar logs 3000

For Docker containers, runs docker logs -f. For native processes, discovers log files via lsof and tails them.

Watch for changes:

sonar watch              # poll every 2s, show diffs
sonar watch --stats      # live resource stats
sonar watch --notify     # desktop notifications when ports go up/down

Wait for ports (perfect for scripts):

sonar wait 5432 --timeout 30s              # block until ready
sonar wait 5432 --http                      # wait for HTTP 200
sonar wait 5432 3000 6379                   # wait for multiple

# Example: run migrations after services are up
docker compose up -d
sonar wait 5432 3000 --timeout 60s && npm run migrate

Dependency graph:

sonar graph              # show which services talk to each other
sonar graph --dot        # Graphviz DOT format

Profiles (save expected ports):

sonar profile create my-app    # snapshot current ports
sonar up my-app                # check if expected ports are running
sonar down my-app              # stop all ports in the profile

Find free ports:

sonar next                     # first free port from 3000
sonar next 8000                # first free port from 8000
sonar next -n 3                # 3 consecutive free ports

Port forwarding:

sonar map 6873 3002            # proxy 6873 → also available on 3002

How Does Sonar Compare to Alternatives?

Feature	`lsof \| grep`	Sonar	Portless
List ports	✅ Manual parsing	✅ Clean table	N/A
Docker awareness	❌	✅ Container names, images	N/A
Kill by port	❌ Multi-step	✅ `sonar kill 3000`	N/A
View logs	❌	✅ `sonar logs`	N/A
Wait for ready	❌	✅ `sonar wait`	N/A
Avoid port conflicts	❌	❌	✅ Named URLs

Sonar + Portless is actually a great combo:

Portless eliminates port numbers with named .localhost URLs
Sonar helps when you need to see what’s actually running

When Should I Use Sonar?

“Port already in use” — see what’s hogging it, kill it
Docker Compose debugging — which containers are actually running?
CI/CD scripts — sonar wait until services are ready before running tests
Resource monitoring — sonar list --stats for CPU/memory per service
Multi-project development — profiles let you snapshot and restore port states

Frequently Asked Questions

What is Sonar CLI?

Sonar is a command-line tool for inspecting and managing services on localhost ports. It shows processes, Docker containers, resource usage, and lets you kill, log, or inspect any service by port number.

How do I install Sonar?

Run curl -sfL https://raw.githubusercontent.com/raskrebs/sonar/main/install.sh | bash or go install github.com/raskrebs/sonar@latest.

Does Sonar work with Docker?

Yes. Sonar detects Docker containers, shows container names, Compose project names, and images. Killing a Docker port runs docker stop automatically.

Can I use Sonar in CI/CD pipelines?

Yes. sonar wait 5432 --timeout 60s blocks until a port is ready—perfect for waiting on database containers before running migrations or tests.

Does Sonar support remote machines?

Yes. Use sonar list --host user@server or sonar watch --host user@server to scan via SSH.

What platforms does Sonar support?

macOS (uses lsof) and Linux (uses ss).

Is there a GUI?

The macOS tray app (sonar tray) shows live port stats in your menu bar. It’s included in the install script.

What license is Sonar released under?

MIT license—free for any use.

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