Hackapong Fun at the Shop!

4 November 2022

Here Comes the Hackapong

Our Yearly hackathon is a very important moment, first of all since we use it to bond and work as a team, and also to use our tools and see what we could add in the future. We used this week to build on tools we already use or that are coming to WDA soon.

Our team decided to put the WDA plugin functionality to good use and we decided to build a pong game that would be playable between two callers using WDA.

To accomplish that feat we used existing tools from the wazo platform as well as webrtc, asterisk, nginx, etc, and some that are not yet available i.e. the plugin interface that is in the works for WDA.

We started by finding a pong javascript codebase that was functional and had all the features we needed. We used an open-source project and we built on that.

The issues we faced were mostly related to synchronisation and control of the paddles for the players.


We wanted it to work with a plastic phone too, so we chose to use DTMFs to control the paddles. For this we had to use the wazo-sdk javascript library. We linked the user controls ( arrow up and arrow down ) to send DTMFs to the stack.

* When using the wazo-sdk we have direct acces to Wazo websocket events 
* without too much work. 
Wazo.Websocket.on('call_dtmf_created', ({ data }) => {

	if (!data.user_uuid) {

	if (data.digit === '0' || data.digit === '1') {
		const isPlayer1 = data.digit === '0';
		return stopMovePlayer(isPlayer1);
	* Since we need to separate both player we sent different DTMF's
	* Through the system.
	const isUp = data.digit === '8' || data.digit === '9';
	const isPlayer1 = data.digit === '2' || data.digit === '8';
	movePlayer(isPlayer1, isUp);

We also had to decide how to synchronise the ball between the two users. Since we are not using a netcode library, we decided to make the caller the source of truth. One of the interesting part is that we are able to speak while playing the game. Oh and if you are very good at pong your calls wont be very long, we needed a way to choose a winner so when you get to 20 points the game ends and the call hangs-up.

setOnGameEndedCallback(idPlayer => {
	Wazo.Phone.sendMessage(JSON.stringify({ type: 'playerWon', idPlayer }), call.sipSession);

The Deployment

Let's make it (not) production ready:

Industrialize deployment

We use ansible to deploy this quickly. Fortunately we already have an nginx service running. First of all, let's create the ansible project.

ansible-galaxy init ansible-role-hackapong
cd ansible-role-hackapong

Let's take a minute to think about it. We need to (1) download a project from git, (2) upload the nginx configuration and (3) enable this new site.

We fill the variables with the necessary values first. For (1)

  • The code repository
  • Path of the cloned project=> /var/www/hackapong

For (2) & (3)

  • Nginx sites-available project name => hackapong
  • A FQDN for the incoming requests => hackapong.wazo.io

The ensuing variable file :

cat defaults/main.yml
# defaults file for ansible-role-Hackapong
project_repo: 'ssh://git@github.com/TinxHQ/hackapong.git'
project_name: 'hackapong'
project_dest_folder: "/var/www/{{ project_name }}"
project_key_file: '/root/.ssh/hackapong_ed25519' # we use a specific key, to keep silos
fqdn: hackapong.wazo.io

The tasks file is as simple as this:

cat tasks/main.yml
# tasks file for ansible-role-hackapong
- name: Download project
    repo: '{{ project_repo }}'
    dest: '{{ project_dest_folder }}'
    version: master
    key_file: '{{ project_key_file }}'
    ssh_opts: '-o UserKnownHostsFile=/root/.ssh/known_hosts'
    force: yes

- name: Upload nginx file
    src: 'nginx.conf.j2'
    dest: '/etc/nginx/sites-available/{{ project_name }}'
  notify: restart nginx

- name: Enable site
    state: link
    src: /etc/nginx/sites-available/{{ project_name }}
    path: /etc/nginx/sites-enabled/{{ project_name }}
  notify: restart nginx

notify clauses above specify a handler, we need to add it in its own file:

cat handlers/main.yml
# handlers file for ansible-role-Hackapong
- name: restart nginx
    name: nginx
    state: restarted

And finally, the template that configures the nginx route:

cat templates/nginx.conf.j2
server {
    listen 80 ;
    listen [::]:80 ;
    server_name {{ fqdn }}; # managed by Certbot

    access_log /var/log/nginx/{{ project_name }}.access.log main;
    error_log /var/log/nginx/{{ project_name }}.error.log;
    root /var/www/{{ project_name }};
    location / {
		return 307 https://$server_name$request_uri;
    location /.well-known {
		root /var/www/html;
		autoindex off;


server {
    listen 443 ssl;
    listen [::]:443 ssl;
    server_name {{ fqdn }}; # managed by Certbot

    access_log /var/log/nginx/{{ project_name }}.access.log main;
    error_log /var/log/nginx/{{ project_name }}.error.log;
    root /var/www/{{ project_name }};
    location / {
		add_header Access-Control-Allow-Origin *;


To deploy all of this, lets write a quick playbook, directly in the role (it is still a Hackathon, don't forget :) )

cat playbook.yml
- hosts: hackapong.wazo.io
  become: true

    - '../ansible-role-hackapong/'

Then we have the hosts file. The ip/hosts are generic (for obvious reasons).

cat hosts
[hackapong.wazo.io] ansible_user=root

Time to deploy:

ansible-playbook -i hosts playbook.yml

Manual steps

Two steps remain, we need to create a domain name for this service and generate its certificate. Using a certificate is not optional as Wazo App won't send requests to a non-secured receiver.

On your favorite cloud provider, create a domain name hackapong.wazo.io. Then ssh on the instance where the plugin is deployed and ask certbot to handle the certificate.

ssh root@hackapong.wazo.io

certbot certonly --webroot --agree-tos -email <infra-team>@wazo.io --expand  -w /var/www/html -d hackapong.wazo.io

Finally, let's restart nginx to make sure the certificate is handled

systemctl restart nginx

And voila !


What is a hackathon without fun and teamwork?

The goal of our project was to use our tools and bond together in a way that would be fun. The use of a game taught our little trio that if a tool , like the plugin interface, is well built then we can develop many more tools using it without a lot of hassle.

Many thanks at Wazo for the opportunity to find another great way to use our tooling, and for the meals, and the housing, and the beer, and the beers, and the b...