Develop Reference

Can I Customize Openfire to use as MBaaS for mobile push notification? How?

I decide to build an infrastructure to send push notification using XMPP Protocol.
I don't want to use 3rd party services like GCM or FCM [because Google restricts FCM service based on IP Address, Is there any other free Android push notification provider? ]. i don't want to use Ejabberd either because it has some cost. i have a plan to configure Openfire on my server with SQL Server so that when a message body with particular recipient(s), added to database somehow, Openfire sends those to proper client(s) [push notification to android devices].
I am developing an XMPP client on Android to connect with this server. i think it doesn't matter what platform i'm working on, anyway it's Android.
can i send message (push notification) from server to client(s) with Openfire? How?
If not, how about Prosody or other XMPP servers?
I appriciate any help

Is it mandatory to use GCM service to show push notification?

I am developing a Cordova app having a Java backend. I want to know if it's mandatory to use GCM service in order to show a push notification in Android/iOS (in notification tray)?
I am using Apache Kafka, MQTT brokers in my backend. Is it possible to show push notification using these solutions, i.e. using completely self defined solutions?
Using MQTT & other brokers I am able to send realtime data to users but how to show those message as native notification in notification bar is my problem.

Yes, you will need to use GCM to send push notifications to Android devices. You can even use GCM to send push notifications to iOS devices (GCM makes request to APNS (Apple push notification service) to make it work).
But GCM for iOS isnt trusted much.
You can use any backend to send push notification to your devices. You just need to make a request to GCM/APNS.
This is the cordova plugin for push notification.
Integrating with GCM is damn easy, but it takes a little effort with APNS.
Most people use third party paid services like Pushwoosh to implement their push backend because its convenient. There is a free alternative OneSignal but it tracks your usage.
Follow this guide to setup push for APNS. (You can just use the Setup certificate part from this guide, since you are not using C#)

To receive push you need use/implement GCM(and actually FCM, because of GCM deprecation)
To show notification from app it is unnecessary to implement GCM/FCM

How to send notification through GCM to Java EE web app?

Recently I had to port my Android app to Java EE enviroment . But I'm struggling with the notification process . For now I use Google Cloud Messaging to send notification from "Server A" to Android devices and can't find any clear method to send the same notification to the Java EE web app .
Here's a diagram to clarify what I want to do :
Any body came through this before ? Please share your thoughts .

Choosing Google Cloud Messaging to send notification is a googd decision. You may implement the XMPP Connection Server protocol. It can receive upstream messages from user's device to cloud. When GCM receives an upstream messaging call from client app, it generates the necessary XMPP stanza for sending the upstream message.
I did some research and found out a java-based server: https://github.com/jarlehansen/gcmutils/tree/master/gcm-test-server
Here's the link for starting GCM with explanation of code: https://developers.google.com/cloud-messaging/

You can't implement push notification for you web app itself.
However you can implement them for different client(browsers).
It's easy to implement gcm push notification on Chrome, you can check Google's Doc on that.
But I don't think Firefox/Safari support gcm.

The difference between GCM and PARSE push messages

I am buiding an android app which will be receiving notifications from my server. This means all my users which is above 1 million, will receive notifications from my server. I know parse and google cloud messaging(GCM) can do the push messages but please I want to know the best out of this two (parse and GCM) so I can implement it. Thanks in advance.

If you look at https://parse.com/tutorials/android-push-notifications you can see:
The Parse library provides push notifications by using Google Cloud Messaging (GCM).
So you have to register your app to GCM console to send push notification in anyway.
When to NOT use parse.com?
If you already have a backend service, you can easily implement push notification since there are plenty of third part libraries for different platforms such as node.js, php etc.
When to use parse.com?
If you don't have backend-service and you just want to send push notifications also if you don't want to spend your time by setting up server stuff then you can go with parse.com
NOTE: Facebook shuts down parse by January 2017 so please consider it.(http://blog.parse.com/announcements/moving-on/)

Android push notification is a service used to send messages directly to the Android Mobile Devices.
There are several ways we can implement Android push notification.
Google Cloud Messaging(GCM)
Parse Notification(Parse.com)
You are asking which one is the best way to implement :
The standard way is using GCM (Google Cloud Messaging) but there are some alternatives like Parse Notification,Which is easier to use.
If you need to handle Json Push messages,Refer this link
Steps involved in send Push notifications:
Developing the application involves two parts:
GCM Server Application – Create Web application using Php to send message to User via GCM Cloud server
GCM Client Application – Create Android application which receive message sent from GCM Server Web App
For More Informations regarding to GCM server and Client Application

Parse uses GCM and uses own service for Kindle

Please Go with google cloud messaging(GCM) .It is very easy to integrate in android app. the problem with parse in some case device token or registration id is not register at their database so User of parse does not get push notification.In case of GCM we can sure for device token
So my recommendation is GCM
Hope this will help you.

Android, push message when app runs?

im developing a app in android. I want to send a push message when the client app is currently running. how can i achieve this with Google cloud messaging. or any other methods? but i want to send the push message at app running stage as well as the app closed. thanks in advance. hope someone will help me...

delay_while_idle attribute in gcm message will make GCM Server send message when device is not idling.
Read about cloud messaging it will help to fully understand how this service works. http://developer.android.com/guide/google/gcm/index.html

You cannot push message on the client side.
You can send REST HTTP data to a server.
On server side - use gcm-server library for pushing gcm messages.