I am posting an answer here, since I had the same error message for a different reason.
This error message can happen, for example, if you are using apache httpd to proxy requests from a source on protocol A to target on protocol B.
Here is the example of my situation:
AH01144: No protocol handler was valid for the URL /sockjs-node/info
In the case above, what was happening was simply the following.
I had enabled mod proxy to proxy websocket requests to nodejs based on path /sockjs-node.
The problem is that node does not use the path /sockjs-node for websocket requests exclusively. It also uses this path for hosting REST entrypoints that deliver information about websockets.
In this manner, when the application would try to open http://localhost:7001/sockjs-node/info, apache httpd would be trying to route the rest call from HTTP protocol to to a Webscoket endpoint call. Node did not accept this.
This lead to the exception above.
So be mindful that even if you enable the right modules, if you try to do the wrong forwarding, this will end with apache httpd informing you that the protocol you tried to use on the target server is not valid.