I've been working on a LAN discovery tool with a Terminal User Interface (TUI) written entirely in Go. It's called Whosthere, and it's designed to help you explore devices on your local network without requiring elevated privileges.

It works by combining several discovery methods:

- mDNS and SSDP scanning

- ARP cache reading (after triggering ARP resolution via TCP/UDP sweeps)

- OUI lookups to identify device manufacturers

It also includes:

- A fast, keyboard-driven TUI (powered by tview)

- An optional built-in port scanner

- Daemon mode with a simple HTTP API to fetch devices

- Configurable theming and behavior via a YAML config file

Why I built it:

Mainly to learn, I've been programming in Go for about a year now and wanted to combine learning Go with learning more about networking in one single project. I've always been a big fan of TUI applications like lazygit, k9s, and dive. And then the idea came to build a TUI application that shows devices on your LAN. I am by no means a networking expert, but it was fun to figure out how ARP works, and discovery protocols such as mDNS and SSDP.

Example usage:

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# install via HomeBrew brew tap ramonvermeulen/whosthere brew install whosthere

# or with go install go install github.com/ramonvermeulen/whosthere@latest

# run as TUI whosthere

# run as daemon whosthere daemon --port 8080

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I'd love to hear your feedback, if you have ideas for additional features or improvements that is highly appreciated! Current platform support is Linux and MacOS.

There's a famous quote:

  Those who cannot remember nmap are condemned to remake it poorly

Rootless nmap scan of a /24 in under 10 seconds:

  nmap -T5 -sn -PR --script broadcast-dns-service-discovery,broadcast-upnp-info 10.0.0.0/24
  …SNIP…
  Nmap done: 256 IP addresses (30 hosts up) scanned in 9.99 seconds

https://nmap.org/book/toc.html

Overall good work. I'd request an `-i` command-line parameter to specify the interface to scan (and I'd prefer ALL params being able to be read from command line params). I think it just performs a full scan initially on my laptop, following scans either didn't success or didn't involve TCP connect scan (I don't see ARP requests after the initial scan).

This is hilarious, 5 years ago I built a very similar cli tool based on the same idea and with the same name (whosthere but in Polish, ktotu [0]). I wonder if you used AI to generate the project and the idea

Congrats for the execution, it looks more complete and feature rich and Go is a better choice for sure

[0] https://github.com/jmaczan/ktotu

Surely a missed opportunity to name it “whogoesthere”

Does the Go standard library have unusually good TUI support or something? Am I just imagining the pattern of new TUIs being written in Go?

Big missed opportunity to call it “Whose LAN is it anyway?”

Have you tried it on Tailscale at all? Could be super useful but sadly TS doesn't support mDNS: https://github.com/tailscale/tailscale/issues/1013

Good skills - you are well on the way to Engineer with a capital E.

You cannot see network traffic.

You'd be amazed at how many people think they can diagnose a network fault without using tools like this. Everyone is an expert until they prove themselves to be a bit of a twit!

At layer 1 you have electrical issues to deal with and that will need some hardware. Obviously you need to pick your network model too. Here you'll go in with a couple of PCs/laptops and APIPA and/or a Fluke or a cheap network tester effort off of Amazon. Use what you have available.

After that you will need nmap and wireshark. LLDP and CDP are very handy too.

If you have to deal with a large network, I can highly recommend Netdisco.

I am not a golang user. If I install as recommended via `go` command on Linux how do I make sure it is updated when new versions are released? I wish it has a .deb package..