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Troubleshooting WebSocket Connections

Polymer uses WebSockets to receive data updates from OctoPrint. Some web proxy configurations break this connection. Solutions for common proxy problems are shown below:

Ngrok Tunnel

  1. Click the wrench icon () in the top-right corner to open OctoPrint settings
  2. Navigate to the ‘API’ section, under the ‘Features’ heading
  3. Enable the ‘Allow Cross Origin Resource Sharing (CORS)’ option

  4. Restart OctoPrint


See this guide from the OctoPrint community forum on how to correctly configure Nginx. In particular, ensure that your Nginx configuration contains the following options:

proxy_http_version 1.1;
proxy_set_header Host $http_host;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "upgrade";



(Thanks Georg for debugging this issue!)

If you are connecting over SSL to HAProxy, your configuration in the backend octoprint section should look like this:

backend octoprint
	reqrep ^([^\ :]*)\ /(.*) \1\ /\2
	reqadd X-Scheme:\ https if { ssl_fc }
	option forwardfor
	server octoprint1
	errorfile 503 /etc/haproxy/errors/503-no-octoprint.http

See this example configuration from this guide

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