Does GRE tunneling support the websocket protocol?
GRE supports all packet types that are routed through it, it's a tunnel after all
You just have to make sure the ports are forwarded to the destination and it's all good.
We generally recommend people run the service right on us, but if they can't (need too much RAM, CPU, etc), then GRE's are great. It isn't uncommon for our clients to just forward all ports like...
iptables -t nat -A PREROUTING -d BUYVM_FILTERED_IP -j DNAT --to-destination 192.168.168.2
That would forward all ports from your filtered down the GRE to the other end.
Francisco