how to schedule a call in asterisk using call file

Daniel Parker

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05-02-2025

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This article explains how to schedule calls in Asterisk using call files. This method allows you to automate outbound calls at predetermined times. We'll cover creating the call file, configuring Asterisk, and troubleshooting potential issues. This is a powerful technique for automating tasks like appointment reminders, mass notifications, or scheduled check-ins.

Understanding Call Files

A call file is a simple text file that contains instructions for Asterisk on how to initiate a call. Asterisk reads these files and initiates calls according to the parameters specified. The key advantage is that you can pre-schedule many calls and have Asterisk execute them automatically. This eliminates the need for manual dialing and allows for efficient, time-controlled outbound calling.

Creating a Call File

Call files typically follow a specific format, and slight variations may exist depending on your Asterisk configuration. However, the core elements remain consistent. A basic call file might look like this:

Channel: Local/1001@internal-context
MaxRetries: 3
RetryTime: 30
Context: outbound-context
Extension: s
Priority: 1
Application: AGI
Data: /var/lib/asterisk/agi-bin/my_agi_script.agi
CallerID: "My Company <123-456-7890>"

Let's break down each line:

• Channel:: Specifies the channel to use. Local/1001@internal-context indicates a call to extension 1001 within the internal-context. Adjust this to match your internal extension or external number.

• MaxRetries:: Sets the maximum number of retry attempts if the call fails.

• RetryTime:: Defines the time in seconds between retry attempts.

• Context:: Specifies the context in your extensions.conf file to which the call is transferred after connection. You'll likely need a custom context for handling these scheduled calls.

• Extension:: The extension number within the specified context. 's' usually represents the start of a sequence.

• Priority:: The priority within the context. Lower numbers have higher priority.

• Application:: The Asterisk application to execute. AGI (Asterisk Gateway Interface) is commonly used for custom scripting.

• Data:: The path to your AGI script. This script handles further actions, like playing a message or interacting with a database.

• CallerID:: The caller ID to be displayed on the receiving end.

Important Note: Replace placeholders like /var/lib/asterisk/agi-bin/my_agi_script.agi, 1001, and outbound-context with your actual values.

Configuring Asterisk

To use call files, you'll need to configure Asterisk to read and process them. This usually involves configuring a manager interface or using the chan-sccp channel driver (for Cisco phones) to interact with the files.

1. Create the directory: Create a directory (e.g., /var/spool/asterisk/outgoing) where your call files will be stored.

2. Create the outbound context: In your extensions.conf, create a context to handle these calls. This context will likely contain your AGI application call.

3. Schedule the call file creation: You can use a cron job or a custom script to create these call files at the desired times.

4. Monitor and manage call files: Implement a mechanism to monitor the status of calls. A process should regularly check, process, and remove completed or failed call files.

Example AGI Script (my_agi_script.agi)

This script uses the Asterisk AGI (Asterisk Gateway Interface) to handle the call. You'll need to adapt this based on your specific needs. This example plays a pre-recorded message:

#!/usr/bin/env python

import agi

def main():
    agi = agi.AGI()
    agi.verbose("AGI script started")
    agi.stream_file("hello-world") #Replace with your sound file
    agi.hangup()

if __name__ == "__main__":
    main()

Remember to make this script executable (chmod +x my_agi_script.agi) and place it in the directory specified in your call file. You will need to install the python-asterisk-agi package.

Troubleshooting

• Check file permissions: Ensure that Asterisk has the necessary permissions to read and write to the call file directory.

• Review Asterisk logs: Asterisk logs will provide crucial information for debugging. Check for errors in asterisk.log and other relevant log files.

• Verify context and extensions: Double-check your extensions.conf for accurate context definitions and extensions.

Conclusion

Scheduling calls in Asterisk using call files offers a robust and flexible way to automate outbound calls. By understanding the call file format, configuring Asterisk appropriately, and creating custom AGI scripts, you can create a powerful system for managing scheduled communications. Remember to test thoroughly and monitor for errors. This method is invaluable for many applications requiring automated call scheduling.