Unable to Connect to Localhost Printing

Diagnose in order

1. Verify the runtime process and service status locally.
2. Confirm the exact URL: localhost and 127.0.0.1 can be treated differently.
3. Check HTTP versus HTTPS and WebSocket versus secure WebSocket.
4. Verify the configured port is listening and not owned by another process.
5. Inspect the browser console and network panel for refusal, TLS, mixed-content, CORS, or WebSocket errors.
6. Confirm the application origin is paired or allowlisted.
7. Check firewall, antivirus, proxy, VPN, and device-management policy.
8. Compare application SDK and runtime versions.

Error clues

Symptom	Likely area
Connection refused	Runtime stopped, wrong port, or no listener
Certificate error	Local TLS certificate or trust problem
Mixed content	Secure page calling an insecure endpoint
401/403	Authentication or origin authorization
Opens then closes	Protocol/version mismatch or runtime crash

Portix evidence needed

The official endpoint, ports, certificates, pairing flow, logs, proxy behavior, and supported version combinations aren’t documented yet.

Verify

Reconnect after a clean runtime restart, submit one harmless test job, and confirm an unrelated origin cannot connect.