ZeroPort

What is using port 8000?

ZeroPort answers that in the time it takes to double-click a shortcut — and lets you release the port safely.

No installer · No Python · No admin rights · 100% offline

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The problem

You start a service and get this:

OSError: [Errno 10048] error while attempting to bind on address
('127.0.0.1', 8000): only one usage of each socket address is
normally permitted

So you open a terminal, run netstat -ano | findstr :8000, copy the PID, run tasklist /fi "pid eq 12452", and end up looking at python.exe — which tells you nothing, because you have four of those running.

ZeroPort is that whole loop, as one window.

It is a single-window Windows desktop utility that lists every listening TCP port on your machine, names the process behind it, works out what that process probably is, and gives you one deliberate way to stop it.

That is the whole product. It is not a task manager, a system monitor, or a network analyser, and it will not grow into one.

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Install

⬇ Download ZeroPort.exe — one file, 34 MB, nothing to install.

1. Download it.
2. Double-click it. Right-click → Send to → Desktop if you want a shortcut.

Windows SmartScreen shows a warning the first time ("Windows protected your PC"), because the binary is not code-signed. Choose More info → Run anyway.

If you would rather verify before running, every release publishes the executable's SHA-256:

Get-FileHash ZeroPort.exe -Algorithm SHA256

Prefer to build it yourself from source? See Building ZeroPort.exe.

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Features

• Real listening TCP ports, read straight from the Windows connection table — never sample data.
• Process identity: name, PID, executable path, command line, owner.
• Descriptions that use evidence. python -m uvicorn main:app becomes FastAPI / Uvicorn; next dev becomes Next.js. A port number alone is treated as weak evidence, so a bare python.exe on 5432 stays Python process instead of pretending to be PostgreSQL.
• Your own names. Map 8000 → AI Backend and it overrides everything else.
• Instant search across port, process, PID, address and description.
• Manual refresh and auto-refresh (2 / 5 / 10 / 30 seconds, or off; 5 seconds by default).
• Safe termination: confirm, revalidate the process identity, terminate gracefully, escalate only if needed, then rescan.
• System-process protection. Windows core processes show PROTECTED and have no stop action.
• Multiple ports per process are shown accurately, with a violet marker on the PID and the full port list in the confirmation dialog.
• Works entirely offline. No account, no telemetry, no network calls.

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Tech stack

Piece	Choice	Why
UI	PySide6 (Qt Widgets)	Native window, no browser, fast start
System access	psutil	One well-tested API for sockets and processes
Packaging	PyInstaller	Single .exe, no Python needed on the target machine

PySide6-Essentials is used rather than the full PySide6 meta-package: the app only needs QtCore, QtGui and QtWidgets, and the extra ~140 MB would otherwise end up inside the executable.

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Development setup

python -m venv .venv
.venv\Scripts\activate
pip install -r requirements-dev.txt

Run it:

python -m app.main

Requires Python 3.11 or newer on Windows 10/11.

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Testing

python -m pytest

The suite runs against the real operating system rather than mocks: it binds actual sockets and checks they appear, spawns real child processes and stops them, and forces the awkward paths — a PID that exits first, a PID reused by another process, an access-denied terminate, a process that ignores terminate(), a config file with a typo in it.

tests/test_end_to_end.py drives the whole product once: it starts a real listener, waits for the real window to show it, clicks the STOP cell through Qt's event system, accepts the confirmation dialog, and checks the port is released and the row disappears on its own. The UI tests run headless under Qt's offscreen platform, so no desktop session is needed.

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Building ZeroPort.exe

build_windows.bat

The script creates the virtual environment if needed, installs dependencies, generates the icon, runs the tests, and only then packages. Use build_windows.bat --no-tests to skip the test run.

Result:

dist\ZeroPort.exe

It is a single windowed executable — no console window appears — and runs on a Windows machine with no Python installed. Right-click it and Send to → Desktop to make a shortcut.

To rebuild the icon by itself:

python tools\make_icon.py

Publishing a release

Tagging a commit builds the executable in GitHub Actions and attaches it to a release, so the published binary is always reproducible from tagged source:

git tag v1.0.0
git push origin v1.0.0

The workflow is .github/workflows/release.yml. It installs dependencies, generates the icon, runs the full test suite, builds, and publishes only if all of that passes.

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Configuration

Settings live in a single file:

%APPDATA%\ZeroPort\config.json

{
  "auto_refresh": true,
  "refresh_interval": 5,
  "window": { "width": 1100, "height": 700, "maximized": false },
  "custom_descriptions": {
    "8000": "AI Backend",
    "3000": "Frontend",
    "9000": "MCP Server"
  }
}

Edit it by hand, or use the NAMES button in the app. Custom descriptions override automatic inference and are shown in lime so you can tell them apart.

A malformed config never blocks startup. Individual invalid values fall back to the defaults and the rest of the file is still used. If the file cannot be parsed at all, it is kept as config.invalid.json rather than overwritten, so a stray comma never costs you your port names.

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Administrator permissions

ZeroPort deliberately does not require elevation.

Without it you can see every listening port on the machine and stop anything you own — which covers essentially all development servers. Processes owned by SYSTEM cannot be inspected in full or terminated; ZeroPort says so plainly rather than failing silently, and suggests running as Administrator when that is the actual blocker.

The app never elevates itself and never runs shell commands.

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Keyboard

Key	Action
F5 / Ctrl + R	Refresh
Ctrl + F	Focus search
Esc	Clear search
Enter / double-click	Process details
Right-click	Details, copy port, copy PID, stop

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Known limitations

• Windows only. The protection rules, address formatting and packaging are written for Windows 10/11. The service layer would mostly work elsewhere; the judgement about what is safe to kill would not.
• Listening TCP only. UDP endpoints and established connections are out of scope by design — they are not what "port already in use" means.
• Some sockets have no visible owner. Windows hides the owning PID of a few system sockets. Those rows appear with UNKNOWN status and no stop action.
• Descriptions are inferences. They are drawn from the command line and executable name, and they stay vague when the evidence is weak. If ZeroPort says Python process, that is the honest answer, not a failure.
• No stop-all. Releasing ports is intentionally one decision at a time.

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Built by Tahir Nazir — its-tahir.com