public ApnsServiceBuilder withGatewayDestination(String host, int port) {
        this.gatewayHost = host;
        this.gatewayPort = port;
        return this;
    }
Specify the gateway server for sending Apple iPhone
notifications.

Most clients should use {@link #withSandboxDestination()}
or {@link #withProductionDestination()}.  Clients may use
this method to connect to mocking tests and such.

@param host  hostname the notification gateway of Apple
@param port  port of the notification gateway of Apple
@return  this
src/main/java/com/notnoop/apns/ApnsServiceBuilder.java