Introduction

As part of the OEP platform at my previous college, we designed an SMS subsystem for messaging Danish mobile phones. It was intended for alerts like account lockouts or password resets. I coded it in Python.

The Scenario

We used LDAP as a central user database. The script needed to accept either a phone number or username, then look up the mobile number via LDAP (mobile attribute). I used python-ldap for this, available via Ubuntu’s package system.

There were two usage modes:

  • Without a database (direct send)
  • With a database queue (MySQL), to delay non-urgent messages

I wrote the SMS send script as a module to be reused by the database-driven queue script.

The System

There are three parts:

  1. SMS Sender: Sends messages via HTTPS
  2. SMS Insert: Adds a message to the database
  3. SMS Database: Cronjob script that checks and sends queued messages

LDAP Integration

The common library used in other RTGKom.dk scripts provided the getMember(userid) function. From there, we could get the mobile number:

def GetNumber(value):
    try:
        return int(value)
    except:
        pass

    cl = commonLibrary()
    user = cl.getMember(value)
    return int(user['mobile']) if 'mobile' in user else 0

SMS Send Script

We used CPSms.dk as a gateway. Their API PDF helped build the HTTPS requests.

I used optparse to parse command-line arguments. The script builds a query URL and sends it if SMS_ACTIVE = True. Here’s a snippet:

if SMS_ACTIVE:
    response = urlopen(SMS_SERVER + url).read()
else:
    response = "<error>SMS_ACTIVE: False</error>"

SMS Insert Script

This script inserts a message into the MySQL todo table:

sql = """
INSERT INTO `todo` (`sfrom`, `srecipient`, `smessage`, `spriority`, `sstatus`, `sdate`)
VALUES (%s, %s, %s, %s, 'todo', CURRENT_TIMESTAMP);
"""

It also supports a --highpriority flag to bypass timing rules.

SMS Database Script

This script is meant to run periodically (e.g., every minute via cron). It handles timing rules like:

SMS_MAXPRDAY = 10
SMS_HOURLOW = 7
SMS_HOURHIGH = 22

It sends queued messages only within defined hours, unless marked high priority.

Result

The system worked reliably—minus a bug related to nonexistent users (fixed). With or without the MySQL layer, it’s flexible and free to use.

LDAP integration makes it suitable for organizations, but the system can run independently as well.

All in all: success. ✅