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Sometimes you need to be able to send SMS from a computer. This is obvious when you’re talking of monitoring your servers. Email alerts are good, but what if you’re sleeping ?
I used to set up a SMS modem, with it’s own SIM card and subscription. This is really easy, using smsd daemon, to send SMS. Just put a formated file in a directory and bam!, you SMS is fired.
But what when you can’t set a SMS Modem in a datacenter ?

Then you have to use an online SMS provider.

  • Good

    • you just have to call an API to send a SMS

  • BAD

    • it’s not free (you pay per SMS when the modem can have an unlimited SMS sending subscription
    it is network dependant ; if you have a network failure, you will never be informed

    Once you know that, you can start using it.
    I will set up two monitoring plateforms : one inside the datacenter, monitoring every services and local network and one outside, on a hosted server somewhere else, to check the network connecivity of the datacenter.

    As our main monitoring is using Nagios, I had to write scripts for it. I now have 2 python scripts : one for sending SMS, one to check how many SMS I have on my account.

    I first had a quick look on the french SMS providers. I chosed www.smsenvoi.com as they are one of the cheapest and the http and mail API are free (yes, some providers make you pay for that !!). They are also based in Marseilles. I’m happy thinking people there can do better than people from Paris :)

    So, let’s dig the http API. You can find it at http://www.smsenvoi.com/pgs_api.php
    It’s quite simple, even if ugly : you send data in POST request, like : userLogin=your.account@domain.com&userPassword=your_password_clear&…
    And call a page, depending on your need :

    • smsEnvoi.php : send a message
    • smsNumber.php : see how many SMS you have availlable in your account
    • smsStatus.php and smsMNC.php : check if a SMS have been sent (this is used when you do mass sending)

    You can do pretty neat things. Just check on their website what the URL’s are.
    To be honest, I only re-write, in a simple way, what the PHP code do but in Python.

    You can find the two scripts attached.
    sendSMS.py take a message from the line input and send it. You have to start it for each recipient. Even if it’s easy to add many recipient at the same time, Nagios can’t do that. I’m just keeping it simple.
    check_sms_free is a script (nagios check formated) to check how many SMS you still have in your account. The Nagios check is defines to be at WARNING state when only 50 SMS are availlable and in CRITICAL state when only 10 are.

    Here are the Nagios config (I do have it in Nconf, but here is what is generated in the statis Nagios file) :

    define command {
    command_name                          host-notify-by-sms
    command_line                          /usr/bin/printf "%b" "Type: $NOTIFICATIONTYPE$ – Host: $HOSTALIAS$ – Address: $HOSTADDRESS$ – State: $HOSTSTATE$ – Date: $LONGDATETIME$ – Info: $HOSTOUTPUT$" | /opt/monitor/nagios/scripts/sendSMS.py –login=$USER8$ –passwd=$USER9$ –smsserver=www.smsenvoi.com –receivers=+$CONTACTPAGER$ –smsfrom=monitor-prod
    }

    define command {
    command_name                          notify-by-sms
    command_line                          /usr/bin/printf "%b" "Type: $NOTIFICATIONTYPE$ – Service: $SERVICEDESC$ – Host: $HOSTALIAS$ – State: $SERVICESTATE$ – Date: $LONGDATETIME$ – Info: $SERVICEOUTPUT$" | /opt/monitor/nagios/scripts/sendSMS.py –login=$USER8$ –passwd=$USER9$ –smsserver=www.smsenvoi.com –receivers=$CONTACTPAGER$ –smsfrom=monitor-prod
    }

    define command {
    command_name                          check_sms_free
    command_line                          $USER1$/check_sms_free –login=$USER8$ –passwd=$USER9$ –smsserver=$ARG1$ -w $ARG2$ -c $ARG3$
    }

    Define the username and password for the smsenvoi account in resource.cfg as $USER8$ and $USER9$

    Then, you can add the check to a host :

    define service {
    service_description                   check_sms_free
    check_command                         check_sms_free!www.smsenvoi.com!50!10
    host_name                             localhost
    check_period                          24×7
    notification_period                   24×7
    contact_groups                        admins,sysadmins
    event_handler_enabled                 0
    active_checks_enabled                 1
    passive_checks_enabled                1
    notifications_enabled                 1
    check_freshness                       0
    freshness_threshold                   86400
    use                                   Default_timeperiod_interval_5
    }

    Don’t forget to define the cellphone number of each users in the « PAGER » field :

    define contact {
    contact_name                          @lecentre.net-sms
    alias                                  sms lecentre
    host_notification_options             d,r
    service_notification_options          c,r
    email                                 @lecentre.net
    pager                                 +33682887766
    host_notification_period              24×7
    service_notification_period           24×7
    host_notification_commands            host-notify-by-sms
    service_notification_commands         notify-by-sms
    }

    Note the format of the phone number, with international format, starting with +
    And voila…
    Find the two scripts here : sendSMS.py and check_sms_free

    Todos :
    - limit the message size to 160 caracters, which is the max for a single SMS. If you send messages longer, they will count as two SMS.
    - catch every exception in the httplib Python framework (this is really basic for the moment)