Sending SMS Text Messages Using Python

For one of my Pi projects I wanted the ability to send SMS text messages from a Python script. These messages would be sent to my mobile phone and alert me about specific events recorded by my Pi. There was no possibility of connecting the Pi to a mobile phone so I decided to send the SMS via the internet.

In previous years there were services that allowed you to send free text messages via the Internet. In general these services were either illegal or relied on loopholes in mobile phone networks that have since been fixed.

So the only reliable solution is to use an SMS Gateway.

SMS Gateways

Sending messages via a legitimate gateway costs per message but this cost is low (approximately 5p per message) and you know the service will be available and reliable.

I decided to use TxtLocal as they provided a low cost solution with the added bonus of example Python code to send messages from within a script. They provide full documentation on their SMS API Gateway page which includes code examples for PHP, ASP, C#, VB .Net, VBA, Java and Perl as well as Python. This was perfect for my Raspberry Pi project.

Step 1 – Create an Account

It was quick and easy to sign up for a free account. This gives you 10 free messages so you’ve got a chance to test your code before having to pay for more messages.

Step 2 – Get Your API Hash

You can get your unique API hash from the TextLocal Control Panel. You must enter your API hash into the example script below. Note : This is not the same as the “API Key”.

Step 3 – Example Python Code

Create a Python script on your Pi named “sendsms.py” and include the following content :

#!/usr/bin/python
#-----------------------------------
# Send SMS Text Message using Python
#
# Author : Matt Hawkins
# Site   : https://www.raspberrypi-spy.co.uk/
# Date   : 29/06/2018
#
# Requires account with TxtLocal
# http://www.txtlocal.co.uk/?tlrx=114032
#
#-----------------------------------
# Import required libraries
import urllib      # URL functions
import urllib2     # URL functions

# Set YOUR TextLocal username
username = 'joebloggs@example.com'

# Set YOUR unique API hash (NOT API Key)
# It is available from the docs page
# https://control.txtlocal.co.uk/docs/
apihash = '1234567890abcdefghijklmnopqrstuvwxyz1234'

# Set a sender name.
# Sender name must alphanumeric and 
# between 3 and 11 characters in length.
sender = 'RPiSpy'

# Set flag to 1 to simulate sending
# This saves your credits while you are
# testing your code.
# To send real message set this flag to 0
test_flag = 1

# Set the phone number you wish to send
# message to.
# The first 2 digits are the country code.
# 44 is the country code for the UK
# Multiple numbers can be specified if required
# e.g. numbers = ('447xxx123456','447xxx654321')
numbers = ('447xxx123456')

# Define your message
message = 'Test message sent from my Raspberry Pi'

#-----------------------------------------
# No need to edit anything below this line
#-----------------------------------------

values = {'test'    : test_flag,
          'username': username,
          'hash'    : apihash,
          'message' : message,
          'sender'  : sender,
          'numbers' : numbers }

url = 'https://api.txtlocal.com/send/'

postdata = urllib.urlencode(values)
req = urllib2.Request(url, postdata)

print('Attempt to send SMS ...')

try:
  response = urllib2.urlopen(req)
  response_url = response.geturl()
  if response_url==url:
    print('SMS sent!')
except urllib2.URLError, e:
  print('Send failed!')
  print(e.reason)

This script can be downloaded directly to your Pi from BitBucket using :

wget https://bitbucket.org/MattHawkinsUK/rpispy-misc/raw/master/python/sendsms.py

or by using this link.

You can edit the script at anytime using :

nano sendsms.py

Step 4 – Run & Send SMS

Assuming your Pi is connected to the Internet you can then run the script using :

python sendsms.py

If everything has worked you should see “SMS Sent!” displayed on your screen.

While you are testing you can make use of the “test_flag”. This allows the script to run but without using up your credits. Make sure you enter your own user name, hash and target mobile phone number. If everything looks good set the flag to “0” and run the script again. This will send a real message to your phone and deduct 1 credit from your TxtLocal account.

Once you’ve used up your initial 10 free messages you can buy additional credits. How expensive this facility becomes is really down to how many messages you get your Pi to send. For my purposes I only intend on sending a few hundred per year.

Important Notes

• You must edit the script to include YOUR own API hash and YOUR own username.
• As each message will use up your credits on TxtLocal so you should consider carefully how many messages your script sends. Any programming mistakes may result in you sending more messages than you planned.
• Make sure you enter the mobile phone number correctly so you do not send messages to the wrong person.
• The link I provide above to TxtLocal is an affiliate link. This means if you sign up using it any purchases you make via their system will earn me a small amount of commission. You don’t have to sign up via this link if you don’t want to but there is no reason not to.