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# WebSocket, firewall, or Cloudflare blocking SimplyPrint (live data, Cloud Slicer)

# WebSocket, firewall, or Cloudflare blocking SimplyPrint (live data, Cloud Slicer)

**Symptoms this article covers:** the panel loads but live printer status never appears, the "Connecting…" banner stays forever, the Cloud Slicer hangs without finishing, file uploads fail, you're on a school / office / enterprise network, or multiple websites are slow at the same time.

These are network problems, not browser problems. The browser is fine - the connection between you and SimplyPrint (or one of its dependencies) is the bottleneck.

## What SimplyPrint needs to reach
At minimum, your network has to allow:

- **HTTPS** (TCP 443) to `simplyprint.io` and `*.simplyprint.io`
- **WebSocket (WSS)** to `ws.simplyprint.io` - live printer status, panel updates
- **SSE (Server-Sent Events)** to `slicing.simplyprint.io` - Cloud Slicer streaming
- **Third-party scripts** from `js.stripe.com`, `cdnjs.cloudflare.com`, `client.crisp.chat`

The complete list (with ports and reasoning for your IT department) lives at [simplyprint.io/hardware-network-requirements](https://simplyprint.io/hardware-network-requirements). Send that link to your network admin.

## 30-second test: try mobile data
Turn your phone's mobile hotspot on, connect your computer to it, reload SimplyPrint.

- **Works on hotspot, fails on your normal network:** the cause is your network or its firewall.
- **Fails on both:** not a network problem.

## "Connecting…" forever (WebSocket blocked)
The panel loads but live printer data never appears. The banner at the bottom keeps saying "Connecting…". Almost always: WSS to `ws.simplyprint.io` is blocked. Common on enterprise and school networks. Ask IT to allow WebSocket traffic to `*.simplyprint.io`.

See [How SimplyPrint sends prints / Gcode to the printer](https://help.simplyprint.io/en/article/how-does-simplyprint-send-prints-gcode-to-the-printer-usb-serial-connection-how-it-works-1hrhbce/) for the WebSocket architecture context.

## Cloud Slicer hangs (SSE blocked)
You start a slice and the progress bar stalls. The Cloud Slicer uses SSE over `slicing.simplyprint.io`, which some restrictive firewalls block as an "unknown protocol". Same fix: allow SSE to `*.simplyprint.io`.

## Slow networks (Starlink, congested Wi-Fi, distant VPN)
Browsers time out long requests by themselves, regardless of our generous server-side timeouts.

- **Satellite (Starlink, Viasat):** high latency causes intermittent failures
- **Heavily-shared Wi-Fi** (dorms, cafes, conferences)
- **VPNs in distant regions** (200+ ms added round-trip)

If the panel detects you're on a slow or metered connection, your debug report will show it under `network.effectiveType`. Hard-wired Ethernet usually helps more than tweaking the browser.

## Cloudflare / ISP routing problems
SimplyPrint sits behind Cloudflare, like a large chunk of the internet. A few times a year, certain ISPs in certain regions get re-routed badly through Cloudflare's network and a lot of sites misbehave at once. A well-documented recent example: [Deutsche Telekom users in Germany were re-routed through suboptimal Cloudflare paths](https://wotschofsky.com/blog/telekom-cloudflare-routing).

If many of your sites are slow at the same time, check:

- [Cloudflare status](https://www.cloudflarestatus.com/)
- [Cloudflare on downdetector](https://downdetector.com/status/cloudflare/)
- [Third-party services status hub](https://03rn8k9ib2gwifde.incidenthub.net/)

Workaround: switch to mobile data (different network path).

## Printer-side connectivity
If the panel works fine but a specific printer says "offline", the printer's own network connection is the issue, not yours. See:

- [Why is my printer offline?](https://help.simplyprint.io/en/article/why-is-my-printer-offline-jzctwn/) (generic)
- Brand-specific: Bambu, Prusa, OctoPrint, Klipper, UltiMaker, Elegoo, Duet - search the helpdesk for "Why is my [brand] printer offline?"
- [Troubleshooting Klipper / Moonraker setup](https://help.simplyprint.io/en/article/troubleshooting-klippermoonraker-setup-with-simplyprint-1me0aec/)

## Edge case: DevTools "Block request URL"
If you've been debugging in DevTools yourself: the Network tab has a "Block request URL" feature. It's persistent and easy to forget. Close DevTools, reopen, check the blocking list, clear anything leftover.

## Related articles
- [Cloud Slicer troubleshooting overview](https://help.simplyprint.io/en/article/cloud-slicer-troubleshooting-overview-14x34wr/)
- [Slice failed: what the error means and what to send support](https://help.simplyprint.io/en/article/slice-failed-what-the-error-means-and-what-to-send-support-2q2j2g/)
- [How to slice, preview, download, and send sliced files](https://help.simplyprint.io/en/article/how-to-slice-preview-download-and-send-sliced-files-7dw6vc/)