Skip to content
XMPP Connection Server for FCM using the latest version of the Smack library (4.2.4) + Connection Draining Implementation
Branch: master
Clone or download
Pull request Compare This branch is 77 commits ahead of yatharthranjan:master.
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.

Important Info

This repository is an extended version of FCM XMPP Connection Server 2 (its fork) which adds support for scheduling notifications for clients which send the details of the notifications to be scheduled via a FCM upstream message. The corresponding android client is located at FCM Test Android Client and the cordova client is located at Cordova client which uses this fcm plugin The following changes have been introduced -

  1. The maven build has been converted to a gradle build and several improvements to the build process.

  2. Added a command line parser for arguments and also looks in environment variables for these values.

  3. Added notification scheduling function by parsing payloads from upstream messages containing the action SCHEDULE. The format of the data payload of upstream message should contain atleast

            "notificationTitle":"Schedule id 1",

    If ttlSeconds is not specified the default is set to 28 days. Note that the time parameter is in milliseconds (from epoch time) while the ttlSeconds is in seconds as apparent from its name.

  4. Currently it supports 3 types of schedulers - simple, in-memory, persistent and server. As the name suggests, simple is just a java thread based scheduler without any DB, in-memory uses an instance of in-memory database, persistent writes database files to disk and server uses an an instance of database server allowing for concurrent access from other apps. We use the HyperSQL DB or HSQL in short as it supports in memory, persistent and server options.

  5. To locally build the xmpp server and run it -

    ./gradlew clean build

    Then you can just run the jar file generated or any of the distribution files with -h or --help option to display the usage -

    java -jar radar-xmppserver-all-0.1.0-SNAPSHOT.jar --help

    or install package into /usr/local using the distribution

    sudo tar -xzf build/distributions/radar-xmppserver-0.1.0-SNAPSHOT.tar.gz -C /usr/local --strip-components=1

    Now you can run with command

    radar-xmppserver --help

    Run again by specifying the options you find in the above help -

    radar-xmppserver [Options]
  6. Notifications can be cancelled using the data below from an upstream message -

            "action": "CANCEL",
            "cancelType": "all",
            "subjectId": "yatharth"
  7. A Dockerfile is also included with the project for running the server in a docker container. Build the docker image by running the following in the root directory -

    docker build -t "radarbase/radar-xmppserver:0.1.0" .

    Then run the container like to get all the available options -

     docker run radarbase/radar-xmppserver:0.1.0 --help

    Then run with the options -

    docker run radarbase/radar-xmppserver:0.1.0 [Options]
  8. Using it with docker-compose is also possible. Just add the following to the docker-compose.yml file under the services tag -

        image: radarbase/radar-xmppserver:0.1.0
        restart: always
          RADAR_XMPP_FCM_SENDER_KEY: <your-sender-key>
          RADAR_XMPP_FCM_SERVER_KEY: <your-fcm-server-key>
          RADAR_XMPP_SCHEDULER_TYPE: <scheduler-type>
          RADAR_XMPP_DB_PATH: <db-path(if using db scheduler)>
          - ./myhostdir/hsql/:/usr/hsql/


        image: radarbase/radar-xmppserver:0.1.0
        restart: always
        command: -s <sender-id> -k <server-key> -ns <notification-scheduler-type> ...
          - ./myhostdir/hsql/:/usr/hsql/
  9. As seen above the options can be either set as command line args or as environment variables. The docker image is also published on Docker hub radarbase/radar-xmppserver. Also make sure to mount the path of the db as a bind mount to host if using a persistent db otherwise all data will be lost if the container is removed.

  10. Examples of docker-compose builds are included in the /docker directory along with a Dockerfile for building and running hsql server in a docker container. These can be used for development or modified for production deployments.

  11. By default, the application logs all messages to file at the path /usr/local/radar/xmpp-server/logs/, please make sure to mount your host path to this path to persist the log files. This creates separate rotating files base on time for DEBUG level(and higher, means including all messages except TRACE) and ERROR level(and higher).

Old README from base

XMPP Connection Server for FCM (Upgrade from Smack 3.x to 4.x) + Connection Draining Implementation

This is an upgrade of my last FCM XMPP Connection Server application. Now, this project uses the latest version at this time of the Smack library (4.2.4). I just added the connection draining implementation to this project. If you had some problems check my troubleshooting section!

The new version has introduced new terminology, deprecated some older methods and enriched the library in general. The problem started when there is a no working example out there using the new version to build a XMPP CCS for FCM. In summary, the API changes from the 3.x to the 4.x version are:

  1. XMPPConnection is now an interface. Use either AbstractXMPPConnection or one of its subclasses (XMPPTCPConnection).
  2. XMPPConnection.addPacketListener is deprecated: use either addAsyncPacketListener or addSyncPacketListener.
  3. Packet became a deprecated interface. Use the new Stanza class.
  4. The Packet Extension term is now Extension Element.

For more information you must read the following documentation:


New Smack libraries

How to start the server

Just because it is the same project as my prior solution, the way to start the server is exactly the same. You can read my how to start the server.


This is a simple java code. You can integrate with just spring or spring in a container (Tomcat for example). In any case you need to take into account these issues:

  1. If using a simple java application, keep the application alive listening messages. This problem occurs when you use a simple java code as a daemon in linux (that's why I put the while true workaround).

  2. If using a java server (with spring boot at least), close the XMPP connection when the server goes down. This problem occurs when even if you shutdown the server the XMPP connection is still open and handling incoming messages. I do not know yet if this is a spring boot problem. The thing is like we are wrapping the XMPP CCS Server into a HTTP interface just to treat it as a normal server. My workaround was putting the disconnection in the spring preDestroy. @PreDestroy public void springPreDestroy() { //ccsConnection.disconnect(); }

  3. Reconnection when connection draining. The reconnection should be handled to connect again to the FCM using the same parameters with a backoff strategy. Smack can handle the automatic reconnection if you enable it but if the connection will be closed from the FCM side you should call your reconnection method when FCM sends connection draining control message or connection draining error message.

  4. Handle properly the new connection creation. If you handle differently the connection draining or use the reconnect. Always make sure that when you create a new connection the old one is completely closed gracefully to avoid phantom connections!

About me

I am Carlos Becerra - MSc. Softwware & Systems. You can contact me via:


To tell the truth. I was really worried looking for the right solution. Finally, I made a list of useful links (apart from the above documentation links).

Any improvement or comment about the project is always welcome! As well as others shared their code publicly I want to share mine! Thanks!


Copyright 2016 Carlos Becerra

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   See the License for the specific language governing permissions and
   limitations under the License.
You can’t perform that action at this time.