Erlang Implementation Of Firebase Cloud Messaging Through XMPP Servers
- Android App (Fatalk) -> https://play.google.com/store/apps/details?id=com.kaarss.fatalk
 - Android App Repo -> https://github.com/jeerovan/fatalk
 - App Backend Repo-> https://github.com/jeerovan/firebase_xmpp
 
- Install Erlang (Please Search Google)
 - Clone Repo
 - Execute Command 
makeAt Root Folder Location. This Will Download Required Dependencies And Compile Them. - To Run In A Console, Execute 
_rel/firebase_cloud_messaging_release/bin/firebase_cloud_messaging_release console - Execute Command 
q().To Quit For Now. - You'll Have A Settings File Named : 
settings.txt. It Contains All The Settings You Can Configure To Establish Firebase XMPP Connections And Set Different Limits As Required. - To Establish Firebase Connections, 
fcm_sender_id&fcm_server_keyAre Required. These You Can Find In Your Firebase Project's Cloud Messaging Section - If The 
fcm_connection_limitIs Set To 0 Insettings.txtYou May Initialize A New FCM Connection With Following Command:fcm_manager:create_fcm_process(). - Set Log Levels 
verbose/info/debug/errorTo Control Logs Insettings.txt - After Setting Up Parameters, Execute Console Command To Run And Create FCM Connections
 - To Communicate with external application, establish a unix domain socket over TCP. The default uds location is /tmp/fcm.socket
 
- Supports Only Android For Now (No Support For iOS)
 - Sends Only 
dataNotifications With Priority (high/normal) Having TTL 0 To Improve Latency - Sends Bundle Of Messages To Optimize Bandwidth
 - Does Not Support Delivery Receipt
 - Automatic Retry Of 
nackMessages - Configurable Paramters To Control Throughput And Message Rate Per Device
 - Handles Connections With State 
idleOrservice unavailable - Communicate with external application over tcp socket
 
- listen_on : either listen on unix_socket or http_port.
 - unxi_socket : unix_socket location, defaults to "/tmp/fcm.socket"
 - http_port : which port to listen on , defaults to 3000
 - fcm_process_pool_upper_bound : Maxmium number of messages in the pool of fcm_process before it stops accepting further message.
 - fcm_process_pool_lower_bound : Minumum number of messages in the pool of fcm_prcess before it starts accepting new messages again.
 - default_timeout_idle_timeout_milli_seconds : Timeout process polls for new message to process. If there are none, it remains idel for these milli seconds.
 - fcm_connection_service_idle_timeout_seconds : If fcm_process is idle for timeout_seconds, it will be disconnected.
 - fcm_connection_service_unavailable_timeout_seconds : If fcm_process remains unavailable to process any message, it will disconnected after timeout_seconds.
 - fcm_general_message_delay_per_device_nano_seconds : You may even set a delay after consecutive message to be sent to a particular device.
 - fcm_connection_monitor_interval_seconds : After how long monitor process should check fcm_process state and handle accordingly.
 - fcm_connection_limit : Maximum number of fcm_process to established when required.
 - fcm_sent_message_acking_wait_seconds : wait time for a particular message to be acknowledged before it is discarded.
 
The tcp socket sends out following messages to the other end:
- {type:upstream_data, fcm_id:FcmId, data:JsonDataFromTheDevice}
 - {type:fcm_id_updated, fcm_id:FcmId, old_fcm_id:OldFcmId}
 - {type:fcm_id_deregistered, fcm_id:FcmId}
 
And accepts message in following format:
- {fcm_id:FcmId, data:JsonDataToTheDevice}