Learning Paths on AWS:

Build a turn-based game with Amazon DynamoDB and Amazon SNS

Introduction

Background and setup

Provision a database

Set up notifications

Add authentication to your application

Deploy your application

Test your application

Clean up and next steps

Set up notifications with Amazon SNS

When building a turn-based game, you need some way to contact your users to notify them of important events. This includes alerting them that a new game is started, notifying them that it is their turn to play, or informing them that a game has ended.

In this module, you use Amazon Simple Notification Service (Amazon SNS) to notify your users. Amazon SNS is a fully-managed messaging system that allows for pub/sub functionality as well as direct messaging to SMS and email.

Amazon SNS has pay-per-use pricing, so you are only billed for the messages you send. You don’t need to provision throughput ahead of time.

Time to Complete Module: 20 Minutes

  • Send SMS messages via Amazon SNS

    Send SMS messages via Amazon SNS

    There are two different ways to use Amazon SNS. The first way is to create a topic and publish messages to it. You can then configure multiple subscribers to the topic, and each subscriber receives a copy of a message when it is published. This approach is using Amazon SNS in a pub/sub manner and is commonly used for broadcasting messages between services in a microservices architecture.

    The second way to use Amazon SNS is to publish messages directly to a consumer. This method is the approach used in this module. Amazon SNS allows you to publish directly to an SMS number for simple text messaging.

    In the scripts/ directory, there is a sendMessage.js file. The contents of that file are as follows:

    const AWS = require('aws-sdk')
const sns = new AWS.SNS();

const sendMessage = async ({ phoneNumber, message }) => {
  const params = {
    Message: message,
    PhoneNumber: phoneNumber
  }

  return sns.publish(params).promise()
}

sendMessage({ phoneNumber: process.env.PHONE_NUMBER, message: 'Sending a message from SNS!'})
  .then(() => console.log('Sent message successfully'))
  .catch((error) => console.log('Error sending SNS: ', error.message))

    Like in the DynamoDB module, you are importing the AWS SDK for JavaScript in Node.js and creating a client for the service you are using.

    There is a sendMessage function that is similar to a function you have in your application. It takes a phone number and message, and it publishes it as an SMS message.

    At the bottom of the file is an example invocation of that message. You can test this out in your console.

    First, export your phone number as an environment variable. You need to include the country code in the number. If you are in the United States, that country code is 1.

    Use the following command to save and export your phone number, substituting your number for the default listed:

    echo "export PHONE_NUMBER=+15555555555" >> env.sh && source env.sh

    Next, execute the sendMessage.js script by entering the following command in your terminal:

    node scripts/sendMessage.js

    You should see the following output in your terminal:

    Sent message successfully

    You should also receive a message on your phone.

    (Click to enlarge)

    Success! You were able to send a message via Amazon SNS. You use Amazon SNS to notify your users of a number of events in your turn-based game. 

Conclusion

In this module, you learned about Amazon SNS and the different modes of using Amazon SNS. Then, you sent a test SMS message to yourself using Amazon SNS. Amazon SNS is a fully-managed, scalable way to send SMS messages.

In the next module, you configure Amazon Cognito to add authentication to your application.

Next: Add authentication to your application