pub const WS_PORT_SUBPROTOCOL_PREFIX: &'static str;Expand description
The prefix the target port rides behind in a WebSocket handshake.
The subprotocol counterpart of PROXY_PORT_HEADER, and it is present for the same
reason: the token is scoped to a set of ports and the request has to name which one.
Omitting it is the same rejection-that-reads-like-a-bad-token described in the module
docs.