Show HN: Sonar – A tiny CLI to see and kill whatever's running on localhost
github.com
github.com
So I built this lightweight CLI. Single binary, no dependencies. It shows everything listening on localhost with process names, Docker container info, clickable URLs etc.
Sure there are workarounds, but none that satisfied my need for a short, easily rememberable command. Also nothing really has the same satisfaction as running sonar kill 3000 — it just feels nice. I’ve already been approached by a few agent orchestration tools that have been struggling with the same thing. It's really useful when you have multiple agents running, but it's not built for just that use case, I have also find it handy when killing off all containers after a failed cleanup and so on. Also know that MCPs are dead and CLIs are the new thing in agentic coding, this might be a useful tool for Claude, particularly when a compose process exits before all containers are stopped.
Open for contributions, ideas and feedback.
puts 'usage:'
puts 'murder 123 # kill by pid'
puts 'murder ruby # kill by process name'
puts 'murder :3000 # kill by port'Wow, this says more about the agent orchestration tool ecosystem than what you might think, that they're unable to kill child processes they themselves spawn makes it seem like they have zero clue about what they're doing.
Probably why my impression always end up with "Wow, what a vibe-coded mess" when I look through the source of all these harnesses, they don't seem engineered at all.
Yeah, at the bare minimum these projects could also use something like portless[1] which literally maps ports to human- (and language model-)readable, named .localhost URLs. Which _should_ heavily alleviate assignment of processes to projects and vice versa, since at that point, hard-to-remember port numbers completely leave the equation. You could even imagine prefixing them if you've got that much going on for the ultimate "overview", like project1-db.localhost, project1-dev.localhost, etc.
But if your program is some TUI in raw mode its ctrl+c handler is often just killing itself... leaving its children along! Process groups in Unix are a stupid mess and the default being "a process can go away with the subprocess sticking around" rather than the inverse has just caused so many of these long-standing issues.
So why doesn't everyone run local services over Unix sockets?
The only problems: 1) web browsers don't support AF_UNIX URI scheme, and 2) ancient versions of Java don't have built-in APIs for AF_UNIX sockets.
That's it. For these trivial reasons, we've beat our head against arbitrary opaque numbers for decades.
And so, for want of a nail, the Unix was lost.
> The only problems:
3) 40 years of Windows not supporting UDS.
Which is still enough for most portable software to go "eh, localhost is fine*"
* resolving localhost is actually a pretty bad idea (yet very common) and it's way more robust to listen directly on a numeric address.
I like clack/prompts. See its multiselect API.
https://github.com/bombshell-dev/clack/tree/main/packages/pr...
3000 wud (getwud/wud:latest) wud getwud/wud:latest 3000 http://localhost:3000
3001 dockhand (fnsys/dockhand:latest) dockhand fnsys/dockhand:latest 3000 http://localhost:3001I primarily write typescript and python for work. But have dabbled in bunch of other languages at different jobs and for different tasks. Yet to pick up rust, but have been wanting to. But tend to pick what seems most right for the task, while also considering what i most want to be working with
lk() {
if [ $# -eq 0 ]; then
local output=$(sudo lsof -iTCP -sTCP:LISTEN -n -P)
elif [ $# -eq 1 ]; then
local output=$(sudo lsof -iTCP -sTCP:LISTEN -n -P | grep -i --color=always $1)
else
echo "find and kill processes listening on ports. Usage: lk [pattern]"
return 1
fi
if [ -z "$output" ]; then
echo "No listening processes found."
return 0
fi
# Show header + results
echo "$(sudo lsof -iTCP -sTCP:LISTEN -n -P | head -1)"
echo "$output"
echo ""
# Extract unique PIDs (skip the header row if no grep was applied)
local pids=($(echo "$output" | awk '{print $2}' | grep -E '^[0-9]+$' | sort -u))
if [ ${#pids[@]} -eq 0 ]; then
echo "No PIDs found."
return 0
fi
echo "PIDs to kill: ${pids[*]}"
echo -n "Kill these ${#pids[@]} process(es)? [y/N] "
read -r confirm
if [[ "$confirm" =~ ^[Yy]$ ]]; then
for pid in "${pids[@]}"; do
echo "Killing PID $pid..."
sudo kill -9 $pid
done
echo "Done."
else
echo "Aborted."
fi
}sonar list -c port,process,pid,type,url,container
or just show all columns:
sonar list --all-columns
But yeah, it's quite cool. I believe the future lies in software distillation, so cool to see it happen on my own project :D
And I would want someone to use that to one-shot a python implementation. And on and on like a game of telephone until the context degrades so far that it becomes an entirely different program.
I have a tiny shell function to kill whatever is listening on that port
https://github.com/clutchski/dotfiles/blob/main/home/bin/por...
For the even less patient there's also this (not mine): https://github.com/jkfran/killport
Started with the same, but found my self wanting a bit more, so just built it
Although i have a feature branch with a tray app (for macos) that let's you monitor and track any process (will send notifications when one goes up or down). But it's just gimmicks i felt i needed to make life a bit easier when working with compose and across worktrees
Some features on the way are: next available port; wait (wait for a host to return a successful health check before proceeding - good for migrations etc.). And lots more. It's not just about listing running ports, but a tool for managing them.
But to each their own, that's what's lovely about the many options available. But if you have anything in relation to this you think is neat, feel free to open an issue. It may be able to convince you that a simple alias won't suffice.