Free SMS service notifications using Google Calendar

Today I had a small revelation.

I was wracking my brains trying to figure out the SMS messaging provider to use to send myself service outage notifications for my clients’ web sites. Given that I have just a handful of clients so far, it makes no sense to use a provider that requires a minimum monthly or yearly spend.

Ideally of course, I’d like to spend nothing at all, and in exasperation I finally threw my hands in the air (they’re detachable) and whined: “Google sends SMS’s for free – why is it so hard for everyone else?”

(answer: not everyone has billions of dollars)

And then came the revelation: Why not create a command-line tool that uses Google’s Calendar API to create events 6 minutes in the future that have an SMS notification set for 5 minutes prior to launch? That way, within a minute you get a notification sent to your phone for free within 1 minute. Sweet!

So, here’s the code (it’s in Java… sorry)

* Simple command-line notification command that uses Google Calendar ATOM API to create
* a single event 6 minutes in the future with a 5 minute SMS reminder
* @author Daniel Walmsley

import java.util.Date;
import java.util.List;


* This is a test template

public class GCalNotifier {

public static void main(String[] args) {

* Command line args:
* username
* password
* calendar name (e.g. "Notifications")
* TimeZone offset (in hours)
* event start offset (in minutes)
* event end offset (in minutes)
* title
* description

try {

// Create a new Calendar service
CalendarService myService = new CalendarService("GCal Event Notifier");
myService.setUserCredentials(args[0], args[1]);

String calendarName = args[2];
Long tzOffset = new Double(Double.parseDouble(args[3])).longValue() * 60 * 60 * 1000;
Long startOffset = new Integer(Integer.parseInt(args[4])).longValue() * 60 * 1000;
Long endOffset = new Integer(Integer.parseInt(args[5])).longValue() * 60 * 1000;
String title = args[6];
String description = args[7];

// Get a list of all entries
URL metafeedUrl = new URL(
System.out.println("Getting Calendar entries...\n");
CalendarFeed resultFeed = myService.getFeed(metafeedUrl,
List entries = resultFeed.getEntries();
for (int i = 0; i < entries.size(); i++) { CalendarEntry entry = entries.get(i); String currCalendarName = entry.getTitle().getPlainText(); System.out.println("\t" + currCalendarName); if (currCalendarName.equals(calendarName)) { sendDowntimeAlert(myService, entry, title, description, startOffset, endOffset, tzOffset); } } System.out.println("\nTotal Entries: " + entries.size()); } catch (AuthenticationException e) { e.printStackTrace(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (ServiceException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } private static void sendDowntimeAlert(CalendarService myService, CalendarEntry entry, String title, String description, Long startOffset, Long endOffset, Long tzOffset) throws IOException, ServiceException { String postUrlString = entry.getLink("alternate", "application/atom+xml").getHref(); URL postUrl = new URL(postUrlString);//was: "" CalendarEventEntry myEntry = new CalendarEventEntry(); myEntry.setTitle(new PlainTextConstruct(title)); myEntry.setContent(new PlainTextConstruct(description)); Date now = new Date(); Date startDate = new Date(now.getTime()+startOffset); Date endDate = new Date(now.getTime()+endOffset); DateTime startTime = new DateTime(startDate.getTime()+tzOffset); DateTime endTime = new DateTime(endDate.getTime()+tzOffset); When eventTimes = new When(); eventTimes.setStartTime(startTime); eventTimes.setEndTime(endTime); myEntry.addTime(eventTimes); // Send the request and receive the response: CalendarEventEntry insertedEntry = myService.insert(postUrl, myEntry); System.err.println("Got response for: "+insertedEntry.getTitle().getPlainText()); for(When when : insertedEntry.getTimes()) { System.err.println("When: "+when.getStartTime()+" to "+when.getEndTime()); } //5 minute reminder Reminder reminder = new Reminder(); reminder.setMinutes(5); reminder.setMethod(Method.SMS); insertedEntry.getReminder().add(reminder); insertedEntry.update(); } }

Don't forget, you'll need to download the Google Data APIs and put their JARs in your classpath before this will work!

Personally I use this with Nagios. I always use the same args for the calendar offsets, so I've encapsulated most of my settings (except title and body) in a script.


export SCRIPTDIR=/opt/calAlert
export PW=mySecurePassword
export CAL=Notifications
export TZOFFSET=10
export ENDOFFSET=12
export TITLE=$1
export BODY=$2

#export CURRDIR=`pwd`
export CLASSPATH="${SCRIPTDIR}/calAlert.jar"
#assumes GData libs are in "libs" subdirectory of SCRIPTDIR

for jarfile in $(ls "${SCRIPTDIR}/lib")
echo lib/${jarfile}




2 thoughts on “Free SMS service notifications using Google Calendar

  1. Hai Dan,
    I tried your code sample. But i got problem with jar file.
    It doesn’t show any method to call like


    So i get compilation error

  2. Hey Dan,

    We should be able to sort you out. We have a two way SMS system that we have had going for just over a year. We set personal users up with free SMS on a case by case basis. There is a pretty simple HTTP API to use as well.

    Our phone number is on the website ( – drop us a line and we’ll see if we can help.


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