Address already in use: identify the process before stopping anything

Symptoms and scope

Repeatedly starting ComfyUI can collide with an existing healthy instance. A port conflict is not permission to terminate every Python process.

Error fragments for search; IDs, values and filenames may vary:

Address already in use
EADDRINUSE
Only one usage of each socket address

Source-supported context

Operating-system error definitions distinguish an occupied address. A Portable launcher still starts a listening process, so inspect actual processes and addresses rather than counting windows. Source 1 Source 2

Cases to distinguish

1. Another ComfyUI instance already owns the requested port.

2. A different application, container mapping or background service uses it.

3. After a port change, clients or proxies still point at the old endpoint.

Diagnostic sequence

The sequence below is an editorial procedure based on the cited context, not a diagnosis already confirmed for your environment.

Step 1. Use operating-system tools to find the listening PID, then confirm its program, path and purpose.

Step 2. If it is your healthy ComfyUI instance, use it. Save work before a normal stop when a restart is actually needed.

Step 3. For a manually launched or Portable instance, current ComfyUI defines --port (default 8188); confirm how your launcher passes arguments before changing it. Update browser bookmarks, API clients and proxy routing together.5

Step 4. Confirm the new address in startup logs and ensure you are not inspecting the node/model lists of a different instance.

Commands and request examples

Use the environment and shell identified above. Paths and variables are examples to adapt; these commands/snippets were not executed for your machine.

$listeners = Get-NetTCPConnection -LocalPort 8188 -State Listen
$listeners | Select-Object LocalAddress,LocalPort,OwningProcess
$listeners | ForEach-Object { Get-Process -Id $_.OwningProcess | Select-Object Id,ProcessName,Path }

This is a Windows PowerShell example. Replace 8188 with the attempted port from the startup log. Check the local address as well as the port; several listener rows may appear. Process path may be unavailable without access to the process. An empty result alone does not prove that a new bind will succeed; retain the exact startup error.34

Completion check

The intended instance owns the address, and its resources and version match what the client sees.

Limitations and cautions

Do not force-stop an unknown PID. The PowerShell commands above are read-only and their port must match the actual log.

Original sources

• Python errno — rechecked 2026-09-26.
• ComfyUI Portable Windows — rechecked 2026-09-26.

Source and language review: 2026-09-26. No site-run port conflict, process stop, ComfyUI launch or GPU test is claimed.

Related troubleshooting and guides

• Cannot connect to 127.0.0.1:8188: locate the running ComfyUI service
• Value not in list: why a downloaded model does not appear in ComfyUI