Send SMS and MMS Messages In C++

Today we'll use C++, some standard libraries, libcurl, and some POSIX APIs to send SMS and MMS messages using the Twilio REST API. You'll need a (mostly) POSIX-compliant build environment as well as libcurl to follow along with this guide.

Let's get started!

Sign Up for (or Sign In to) a Twilio Account

You'll need to login to your existing Twilio account, or create a new account.

Don't have an account yet? Sign up for a free Twilio trial, post-haste.

Purchase or Find a SMS-Capable Number

You'll need a SMS (or optionally, MMS) capable number to complete this demo. Either use a phone number that you already have, or purchase a new one with SMSes enabled.

From the Twilio Console, here's where you can determine the capabilities of your purchased number:

If you need to purchase a number, after navigating to the 'Buy a Number' link click the SMS checkbox (and the MMS checkbox, if you wish to send media messages).

Prerequisites for This C++ MMS and SMS Guide

We're targeting POSIX Compliant environments with this guide, and tested our code with clang-800.0.42.1 on Mac OSX 10.11, gcc version 4.9.2 on Raspbian 8.0 (kernel 4.4.38-v7+) and gcc 5.4.0 in Cygwin 2.877 on Windows 7 64-Bit.

To build, you will need to ensure you have:

• stdio.h, stdlib.h, unistd.h - C POSIX libraries
• libcurl - Client-side transfer library
• iostream, sstream, string - C++ Standard Libraries

libcurl was already on the Mac. On the Raspberry Pi, you can install a suitable version with:

sudo apt-get install libcurl4-openssl-dev

In Windows 7 and Cygwin, you can install libcurl with Cygwin Setup:

Building cpp_demo

All three environments worked with this example Makefile. You may need to make minor edits - usually to the library search paths - to build in your environment.

On almost all *NIX-type systems (including Windows/Cygwin), building should be very similar to the following lines (you might even be able to copy, paste and execute):

git clone https://github.com/TwilioDevEd/twilio_cpp_demo.git
cd twilio_cpp_demo
make

Send an SMS or MMS Message with C++

We've just built cpp_demo, which attempts to send an SMS or MMS based on your inputs from the command line. src/twilio.cc and include/twilio.hh demonstrate a class, Twilio, which should be easy to integrate into your own codebase. (Note that before putting it into production, you need to add input validation and safety. The first order of concern: the code in its current form can be passed additional HTTP parameters through the command line inputs.)

For C++ developers, our C SMS and MMS guide might give some key insights into the following code - but let's take a closer look to see what's happening under the hood.

• First, we instantiate a Twilio object with our account credentials (find them on the Twilio Console).
• Second, we call the method send_message with the to/from numbers, the message, and optionally a URL to a picture and a boolean of whether we want verbose output.

• Third, once inside the code we first do some exception checking (making sure the message is the proper size), followed by setting up libcurl with our eventual HTTP POST
• Fourth, curl makes the HTTP POST and we clean up with curl_easy_cleanup.
• Finally, we check the response for success or failure, and return the result to the calling function.

Running cpp_demo

Running cpp_demo from the command line is easy once you have it built. Merely set your account credentials and call the code as follows:

account_sid=ACXXXXXXXXXXXXXXXXXXXXXX
auth_token=your_auth_token
bin/cpp_demo -a $account_sid -s $auth_token -t "+18005551212" -f "+18005551213" -m "Hello, World!"
# Optionally, use '-p http://some/path/to/img.jpg' to send an MMS.

Getting C-Rious With Twilio and C++

After this demo, you now have the means to add communications to your new or existing C++ applications. Add monitoring or help to your C++ application, or bring your own use case.

Whether you're a master of the language or closer to a practitioner of "C with classes" please do let us know on Twitter when you've got something built!