Writing WebSocket servers - Web APIs
sec-websocket-protocol: soap, wamp or, equivalently: ...
... sec-websocket-protocol: soap sec-websocket-protocol: wamp now the server must pick one of the protocols that the client suggested and it supports.
...then, in the response handshake, it sends: sec-websocket-protocol: soap the server can't send more than one sec-websocket-protocol header.
...And 2 more matches

Protocol upgrade mechanism - HTTP
sec-websocket-protocol the sec-websocket-protocol header specifies one or more websocket protocols that you wish to use, in order of preference.
... the first one that is supported by the server will be selected and returned by the server in a sec-websocket-protocol header included in the response.
... sec-websocket-protocol: subprotocols subprotocols a comma-separated list of subprotocol names, in the order of preference.

nsIWebSocketChannel
protocol acstring sec-websocket-protocol value.

HTTP headers - HTTP
sec-websocket-protocol ...