This page will explain some basic concepts of SMS Messaging in CommCareHQ.
CommCareHQ uses an SMS Gateway to send and receive messages. This is a system provided by other companies (or cell phone companies) that connects to the cell phone network to send and receive messages. CommCareHQ is connected to different gateways to support different countries.
More information on Dimagi's existing gateways can be found Gateway Options for SMS Projects.
If your country isn't supported by Dimagi's existing gateways you can use an Android-based phone to send and receive messages for your project. This will use the phone's SIM card and SMS balance. Dimagi has partnered with Telerivet to use their system to support Android gateways. The Android phone will connect to CommCareHQ using the internet to know when to send messages and to send incoming messages to CommCareHQ.
Android phones are typically used for low volume projects since cell phone companies usually limit the number of messages that can be sent or received through a regular phone number.
Depending on the gateway used, it can be a short code or a long code. Long codes are similar to regular phone numbers. Short codes are special phone numbers that have a specific name (ex. CommCare) or a shorter phone number and can be used to send a very high volume of messages. Short codes also allow for reverse billing.
When users send a message to your project's SMS gateway, they normally pay a per message cost - this is exactly like them sending a message to a friend. Since this cost can dissuade users from using your messaging system, some gateways are reverse billed. This means that users can send messages for free to the gateway, but you (the gateway) will pay for messages.
There are two types of costs associated with SMS - a monthly software plan cost for CommCareHQ and a per-message cost.
If Dimagi does not have an existing gateway for your country and you'd like to start a larger-scale project, it is possible to connect a new in-country gateway. Obtaining and connecting a new gateway can take a significant amount of time and there are additional costs to connecting it to CommCareHQ. If this is required for your project, please contact us.