public ApnsServiceBuilder withFeedbackDestination(String host, int port) {
        this.feedbackHost = host;
        this.feedbackPort = port;
        return this;
    }
Specify the Feedback for getting failed devices from
Apple iPhone Push servers.

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

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