Throw a useful error when WebSockets are disabled on the server

[analogrelay]

Today the Java Client doesn't do anything with the negotiate payload other than handling redirects. The payload also contains a list of available transports though. Eventually the client will use this to do fallback, but since we only support WebSockets, it should at least check that list to see if WebSockets are available on the server and throw a useful error (The WebSocket transport is not available on the server) if it's not there.

[mikaelm12]

Well we actually do use the negotiate payload to indicate to the user if there were no compatible transports

SignalR/clients/java/signalr/src/main/java/com/microsoft/aspnet/signalr/HubConnection.java

Lines 201 to 203 in e5470d9

	if (!negotiateResponse.getAvailableTransports().contains("WebSockets")) {
	throw new HubException("There were no compatible transports on the server.");
	}

[mikaelm12]

We should add logging though.

[analogrelay]

Wow, I completely missed that :). Good catch.