[Docs] What does 'bad handshake method' mean?

[richb-hanover]

My client's POST request gets back a 400 status, with a response of {"code":2,"message":"Bad handshake method"}. The socket.io connection doesn't get established, and the client never gets any messages from the server. (For more detail, see: #2717)

What does this error response mean? How would I make this happen, if I wanted it to happen?

[richb-hanover]

Update: apparently, (at least one) cause of the 'bad handshake method' is that a POST request arrives without a sid=... parameter in the URL.

In my case, Firefox was not requesting 'Accept: "/"' header, which caused a whole house of cards to fall down. There has been a PR to force that header, and it should be wending its way into the code base. See the discussion in #2717 for way more details.