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 make At 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_key Are Required. These You Can Find In Your Firebase Project's Cloud Messaging Section
• If The fcm_connection_limit Is Set To 0 In settings.txt You May Initialize A New FCM Connection With Following Command: fcm_manager:create_fcm_process().
• Set Log Levels verbose/info/debug/error To Control Logs In settings.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 data Notifications 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 nack Messages
• Configurable Paramters To Control Throughput And Message Rate Per Device
• Handles Connections With State idle Or service 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}