question: public static Observable < NetworkServiceDiscoveryInfo > startDiscovery ( @ NonNull Context context , @ NonNull String protocol ) throws NsdException { if ( protocol . equalsIgnoreCase ( ALL_AVAILABLE_SERVICES ) ) { throw new NsdException ( NsdException . INVALID_ARGUMENT , protocol , 0 ) ; } return DiscoveryOnSubscribeFactory . from ( context , protocol ) ; }
target:  This method is the one that shall be used in order to discover all the services available in the current network for a given protocol. By default, this call will be executed on a proper Scheduler and return the results onto the main thread.<br/>