Sets a request for the given subprotocols.
After the WebSocket
has been built, the actual subprotocol can be queried through WebSocket.getSubprotocol()
.
Subprotocols are specified in the order of preference. The most preferred subprotocol is specified first. If there are any additional subprotocols they are enumerated from the most preferred to the least preferred.
Subprotocols not conforming to the syntax of subprotocol identifiers are illegal. If this method is not invoked then no subprotocols will be requested.