"Establishing a tunnel via proxy server failed."

[Alex Bunting]

Dear all, 

I have written an application using peerJS which connects students (about 20) to a teachers computer. Mostly this is now all working just fine, but in a few incidences (10% ish) students try to connect and get this error:

"Websocket connection to 'ws://0.peerjs.com:9000/peerjs?key=<KEY>&id=<ID>&token=<TOKEN>' failed: Establishing a tunnel via proxy server failed."

The students are all using google chrome, and an up to date version. Most use apple macs of various type. The students who are connecting just fine have the same spec computers in general. They connect via the schools servers.

I figure it must be something on their computers they dont know about. When I asked a student if they had a firewall they said no, but I don't know if they really know...

Does anybody know how this problem might normally arise. If so how i might fix it, and if not how I might narrow down what the problem is.

Thanks, 

Alex

[Michael King]

Is the problem intermittent, or there every time? If the latter, it should be easier to find