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Revision 1 — the current text. The evidence on this page is this revision’s own — it has not been carried forward from, or to, any other revision.

Freeing a port stuck with EADDRINUSE

Identifies what actually holds the port, checks whether it's an orphaned instance of the same app versus a different legitimate service, and verifies the port is free afterward. It does not cover a port genuinely reserved by the OS or blocked by a firewall — EADDRINUSE specifically means something is bound, not that access is denied.

Node.js
Unverifiedno reproductions yetWhy this confidence?
Revision 1published by DevYou curation

Symptoms

The diagnostic path

8 steps, exactly as this revision published them.

  1. Step 1 · StartNode process crashes on startup with EADDRINUSE

    Something else already has this exact port bound. The fix depends on whether that's a leftover instance of your own app or a different service that legitimately needs the port.

    What happens next

    • passed → step 2, Find out what's already using the port

  2. Step 2 · TestFind out what's already using the port

    On Linux/macOS use lsof or ss; on Windows use netstat with findstr, then look up the owning process by PID.

    Read-onlypowershell
    netstat -ano | findstr :8787

    Expected result

      TCP    0.0.0.0:8787           0.0.0.0:0              LISTENING       14832

    What happens next

    • passed → step 3, Is the process holding the port an old instance of this same app?
    • failed → step 4, Nothing is bound to that port right now
    • unknown → step 3, Is the process holding the port an old instance of this same app?

  3. Step 3 · TestIs the process holding the port an old instance of this same app?

    Check the owning PID's command line against this project — a very common dev-mode cause is a previous run (via nodemon or npm run dev) that didn't fully exit.

    Read-onlypowershell
    Get-CimInstance Win32_Process -Filter "ProcessId = 14832" | Select-Object CommandLine

    Expected result

    CommandLine
-----------
node C:\projects\api\src\server.js

    What happens next

    • passed → step 5, Fix: terminate the leftover process
    • failed → step 6, Root cause: a different, legitimate service owns that port
    • unknown → step 6, Root cause: a different, legitimate service owns that port

  4. Step 4 · EndNothing is bound to that port right now

    The port isn't actually in use any more — it may have already been released, or on Windows in particular can briefly show as in-use during TIME_WAIT for a few seconds after a process exits. Re-run and see if it recurs.

  5. Step 5 · FixFix: terminate the leftover process

    Confirm the PID and command line first — force-killing the wrong process can lose unsaved work in whatever it actually is.

    Changes statepowershell

    Changes system or service state. Review before running.

    Force-terminates that process immediately, releasing any port or resource it held.

    taskkill /PID 14832 /F

    What happens next

    • passed → step 7, Confirm the port is free and the app starts

  6. Step 6 · Root causeRoot cause: a different, legitimate service owns that port

    The process holding the port isn't this app — either stop that other service if you don't actually need both running, or change this app's own port (its PORT env var or config) instead of freeing a port something else needs.

  7. Step 7 · Verify the fixConfirm the port is free and the app starts

    Re-check the port, then start the app again.

    Read-onlypowershell
    netstat -ano | findstr :8787

    Expected result

    (no output)

    What happens next

    • passed → step 8, Resolved
    • failed → step 2, Find out what's already using the port
    • unknown → step 2, Find out what's already using the port

  8. Step 8 · EndResolved

    The port is free and the app starts normally.

Sources

Why this confidence?

What would strengthen it: 6 more independent reproductions. Reproductions from 3 more distinct environments.

This counts only what was recorded against revision 1 itself. Nothing reported against another revision is included here — see the revision history for why.