GUI

Workflow

1. Pick an interface. The dropdown shows every NIC on your machine. Use the toggle to hide interfaces with no IP. Hit the ↻ button to re-scan after plugging or unplugging cables.
2. Pick the protocol. LLDP is the universal choice (Aruba, HP, Juniper, Extreme, Cisco, and MikroTik when you’ve enabled it). CDP is Cisco-only. MNDP is the MikroTik-only fallback for RouterOS devices that ship with discovery-protocol = mndp and never speak LLDP.
3. Click Start. Most switches send a discovery packet every 30–60 seconds, so it usually takes a few seconds for the first frame to arrive.
4. Read the result. Switch name, IP, port, VLAN, voice VLAN, MTU, and model populate the result card.

On each platform

Native widgets per platform — same workflow, different chrome.

macOS

Windows

Linux

Privilege warnings

PortFinder shows a banner if it can’t capture packets:

• macOS — click Install BPF Helper once. The app installs a LaunchDaemon that makes /dev/bpf* readable for members of the access_bpf group, which Wireshark also uses.
• Linux — install the .deb or .rpm package. The postinstall sets CAP_NET_RAW on the binary so it doesn’t need sudo.
• Windows — install Npcap with “Allow non-administrators to capture” enabled.

Sniff all interfaces

Selecting Sniff all Interfaces runs a capture on every non-loopback NIC in parallel and returns the first matching packet. Useful when you don’t know which physical port is patched into the switch.

Result card

After a capture lands you get seven rows: Switch Name, Switch IP, Switch Port, VLAN, Voice VLAN, MTU, Switch Model. Fields the switch didn’t advertise render as a muted Not advertised.

• Click any value to copy that one field to the clipboard.
• Copy as JSON copies the full result as pretty-printed JSON — byte-identical to what portfinder capture --json produces, so you can paste it into a ticket or pipe it through jq.
• History (N) opens a popover with the last ten captures. Each row shows a relative timestamp (“2m ago · LLDP on en0 · Gi1/0/24”) plus the switch name and IP. Left-click restores that capture to the card; right-click silently copies the entry as JSON.

History is session-scoped by default; flipping Save capture history in the settings menu writes it to disk so it survives restarts.

Keyboard shortcuts

Action	macOS	Linux / Windows
Start / Stop capture	⌘R	Ctrl+R
Quit	⌘Q	Alt+F4

The shortcut is also wired into the PortFinder application menu as Start/Stop Capture. It’s inert while the settings popover is open, so the popover’s controls keep arrow-key focus.

Settings

A hamburger menu in the title bar opens the settings panel. The popover is grouped into Capture, Logging, About, and a folders row.

Capture

• Save capture history — when on, the History popover persists to a history.json file alongside settings.json. Default OFF. Flipping ON snapshots the current in-memory deque to disk immediately, so quit + relaunch round-trips. Flipping OFF deletes the file; the in-memory deque stays for the rest of the session.

Logging

• Log level — slider with three discrete stops:

  • Normal (info) — lifecycle events only: boot, capture start/stop, settings flips. The default.
  • Verbose (debug) — adds per-event capture diagnostics (“PortFinder isn’t capturing” debugging).
  • Trace — adds per-pcap-tick noise (~20 Hz per interface). Almost always overkill; useful for libpcap timing questions.

  The level applies live to every active logger, including any parallel portfinder capture invocation in another terminal. CLI -v / -vv / -q flags still override at runtime.

• Write debug log — toggles file logging. Default OFF — a fresh install never drops a log file anywhere until you flip the switch. When enabled, log lines go to the platform’s conventional log directory and the toggle takes effect immediately (no relaunch). Rotates at 1 MiB to portfinder.log.1.

About

The About → row opens a sub-page inside the same popover with version, GitHub link, GPL-3.0 license link, and a platform-specific capture-privilege status row (BPF helper on macOS, Npcap on Windows, “Capture access” on Linux). The privilege row is read-only status — installation flows live on the prominent banner up top.

Folders

Two buttons reveal the relevant directories in your file manager.

	Settings folder	Log folder
macOS	~/Library/Application Support/PortFinder/	~/Library/Logs/PortFinder/ (Console.app picks this up automatically)
Linux	~/.config/portfinder/ (XDG config dir)	~/.local/state/portfinder/ (XDG state dir)
Windows	%APPDATA%\PortFinder\	%LOCALAPPDATA%\PortFinder\Logs\ (Local, not Roaming)

The settings folder holds settings.json and (when Save capture history is on) history.json. The log folder holds portfinder.log plus the rotated portfinder.log.1 if you’ve crossed the 1 MiB threshold.