AWS SNS: How to send SMS to a topic, OTP SMS, promotional or transactional SMS

You can send SMS in 2 ways using AWS SNS.

  1. Subscribe to a topic that is already created in AWS SNS and send sms to all numbers who has the subscription.
  2. Send SMS directly to a mobile number.

You can find the following aws doc as a starting point from web and it describes how to create a topic, subscribe a topic and sending sms to the mobile numbers.

https://docs.aws.amazon.com/code-samples/latest/catalog/code-catalog-ruby-example_code-sns.html

For the demonstration purpose, I use Ruby here.

  1. Subscribe to a topic and send SMS
require 'aws-sdk-sns'  # v2: require 'aws-sdk'

sns = Aws::SNS::Resource.new(region: 'us-west-2')

topic = sns.topic('arn:aws:sns:us-west-2:123456789:MySampleTextTopic')

topic.publish({
  message: 'Hello!'
})

This assumes you already created a topic inside your aws console:

Goto AWS Console

  1. Open AWS SNS
  2. Goto Left side -> Mobile -> text messaging sms
  3. Create a topic

You can also follow the above link to perform an API to create topic, subscribe to a topic and send sms

2. Send SMS directly to a mobile number (eg: Send OTP SMS)

Either you can use aws console to send the sms or SNS API.

AWS console:

  1. Open AWS SNS
  2. Goto Left side -> Mobile -> text messaging sms
  3. We are using transactional text messages
  4. Goto publish text message
  5. Select transactional, add mobile number and publish it

Almost all cases we use an API for sending OTP SMS. For that follow the steps.

SNS API – Steps

gem install aws-sdk-sns 
require 'aws-sdk-sns'
otp = generate_otp
set_sns_client
set_sns_client_attrs
response = publish_sms(otp)
  • Generate an OTP
def generate_otp
    (1000..9999).to_a.sample
end
  • Set SNS client
def set_sns_client
    @sns_client = Aws::SNS::Client.new(
      region: ENV['AWS_SNS_REGION'],
      access_key_id: ENV['AWS_SNS_ACCESS_KEY'],
      secret_access_key: ENV['AWS_SNS_SECRET_KEY']
    )
end

  • Set SNS client attributes
 def set_sns_client_attrs
    @sns_client.set_sms_attributes({
                                     attributes: {
                                       'DefaultSenderID' => SENDER_ID,
                                       'DefaultSMSType' => SMS_TYPE
                                     }
                                   })
end

  • Publish SMS
def publish_sms(otp)
    @sns_client.publish({
                          phone_number: @mobile_no,
                          message: "#{OTM_MSG} #{otp}"
                        })
  end

Here ,

OTM_MSG: ‘Your OTP for login is’

SMS_TYPE : ‘Transactional’ or ‘Promotional’

If you want to send OTP, then it is ‘Transactional’. Else if you want to send some promotional sms of your product then it is ‘Promotional’

SENDER_ID: is the sms header that you already registered with TRAI.

The Steps to add Sender ID in AWS is given below:

For example suppose your sender id is: Zomato

Follow the steps to add our SENDER ID – Zomato to AWS SNS

  1. Sign in to the Amazon SNS console – https://console.aws.amazon.com/sns/home
  2. On the navigation panel, choose Mobile, Text messaging (SMS).
  3. On the Mobile text messaging (SMS) page, in the Text messaging preferences section, choose Edit.
  4. On the Edit text messaging preferences page, in the Details section, do the following:
  5. For Default sender ID , enter the provided sender ID to be used (Zomato) as the default for all messages from your account.
  6. Choose Save changes.

If you don’t want to register sender id, then skip this method: set_sns_client_attrs and publish the sms. It take the sms as ‘Promotional’ and sender id will be 8 character random number. Amazon use this type of sms from International route and it costs you almost $0.02 (Rs. 1.5) per sms. Very high rate. So I recommend to register any sender id that resembles your product or company name, from Jio trueconnect (that is free, link given below) and use it in SNS.

If you don’t know how to register sender id, follow this:

For AWS SNS service, there is 2 way of sending sms.

  1. Local route
  2. International route

For local route the price is Rs. 0.20 per sms
For international route the price will be Rs 1.58 per sms – too high

by default AWS SNS use International route

If you are from India follow the TRAI registration
For considering local route we have to register our use case and message templates with TRAI .

So first register here:
https://www.vilpower.in/
as an enterprise / company with all company details and our purpose

These registration requirements are designed to reduce the number of unsolicited messages that Indian consumers receive, and to protect consumers from potentially harmful messages

You can Register in Jio for free:

The link to register:
https://trueconnect.jio.com/#/home/entity-registration
Select Principal entity and continue

Recently Indian Govt made DLT Registration mandatory for sending sms.

Example:
Take Msg from AD-ZOMATO , here ZOMATO is 6 char sender id that we can give in the service provider and send sms before. But now we have to register this in DLT then only our service provider can use this.

After registering DLT we get an ENTITY ID. This entity id need to be attached in our’s otp service provider for sending otp msgs.

If you are using SNS service for the first time you should increase your SMS quota:

AWS says:

If you're new to SMS messaging with Amazon SNS, request a monthly SMS spending threshold that meets the expected demands of your SMS use case. By default, your monthly spending threshold is $1.00 (USD). You can request to increase your spending threshold in the same support case that includes your request for a sender ID

Because Amazon SNS is a distributed system, it stops sending SMS messages within minutes of the spending quota being exceeded. During this period, if you continue to send SMS messages, you might incur costs that exceed your quota.

https://docs.aws.amazon.com/sns/latest/dg/channels-sms-awssupport-sender-id.html

Requesting increases to your monthly SMS spending quota for Amazon SNS:

https://docs.aws.amazon.com/sns/latest/dg/channels-sms-awssupport-spend-threshold.html

Currently, Amazon SNS supports SMS messaging in the following AWS Regions:

https://docs.aws.amazon.com/sns/latest/dg/sns-supported-regions-countries.html

Reference:

https://docs.aws.amazon.com/sdk-for-ruby/v2/api/Aws/SNS/Client.html