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Real-time multimedia and communication in packet networks

Asterisk AGI and Manager Interface. Real-time multimedia and communication in packet networks. Last Practical. Create a calculator application using the Asterisk dialplan E.g. phone an extension

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Real-time multimedia and communication in packet networks

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  1. Asterisk AGI and Manager Interface Real-time multimedia and communication in packet networks

  2. Last Practical • Create a calculator application using the Asterisk dialplan • E.g. phone an extension • * answers and provide an IVR menu saying press 1 to go to the calculator, 2 to go somewhere else, and 3 to go somewhere further • If I press 1 – must be routed to calculator where I am prompted to choose to go to multiplication menu, division menu, add menu or subtraction menu • 1,2,3,4 • Within each menu – prompt user for expression separated by star (*)‏ • So in addition menu, pressing 100*20 should return 120 • While in multiplication menu pressing 100*20 will return 2000 • Results can be played using Festival • After each result should have option of another operation or going to one of the other menus (+-/*)‏ • Remember to check out http://www.voip-info.org/ - Check out the Cut function!

  3. Controlling Asterisk • Number of ways Asterisk can be controlled • Dialplan • Asterisk scheduling (call me)‏ • Asterisk Gateway Interface (AGI)‏ • Manager Interface

  4. AGI • AGI allows us to add functionality to Asterisk with many different programming languages • Java, Perl, PHP, C, Pascal – Anything! • Provides a standard interface through which programs may control asterisk • Used for advanced logic or to communicate with resources such as relational databases and external devices • Allows asterisk to perform tasks that would be otherwise difficult or impossible

  5. AGI – How it works • The AGI script is called from the dialplan‏ • Asterisk and your program communicate via the STDIN, STDOUT and STDERR communications channels (file handles in programming)‏ • Your AGI scripts reads input via its STDIN file handle • Your AGI script writes back to asterisk via its STDOUT file handle • Your AGI program writes error message back to asterisk via its STDERR file handle

  6. Starting your AGI program • Syntax: • exten => extennumber,priority,application,arguments • The application is “AGI” • The argument is the filename of your program • The script must be: • executable (chmod +x filename)‏ • located in /var/lib/asterisk/agi-bin in source versions of asterisk • Located in /usr/share/asterisk/agi-bin in binary vesions of asterisk • Example: Run a perl script agi-test.agi • exten => 1,2,AGI, agi-test.agi

  7. Passing args • exten 1,2,AGI,agi-test.agi|${ARG1}|${ARG2} • AGI programs always receive two args • 1 – path to the AGI script • 2 – Arguments passed from the dialplan • Notes about arguments: • If no arg is given – the arg is empty. • Consists of everything on the line following the verticle bar after the file name, up until the final vertical bar‏ • Quotes are taken as being part of the argument

  8. Communicating with * • Use 'show agi' at the CLI will give you a list of commands • At script startup time, * sends a group of variables to your script which you have to read in • Each item is sent on a line terminated with a newline. The last item is followed by an empty line • agi_request: agi-test.agi • agi_channel: SIP/1000-bcgd162 • agi_language: en • agi_context: mtsietsi • agi_extention: 105 • agi_priority: 2 • Commands sent to * must be terminated with newline

  9. AGI examples‏ • Perl - /usr/share/asterisk/agi-bin/agi-test.agi • Java - /usr/share/asterisk/agi-bin/mosJava.java • /usr/share/asterisk/agi-bin/mosJava.agi

  10. Manager API • A client/server module that allows us to interact with * via TCP/IP • Similar to SMTP and HTTP • Communicates using tags • “header:value” terminated with a newline • First tag must be one of the following • Action: an action requested by the client. • Response: A response to an action from Asterisk • Event: An event reported by Asterisk to the client

  11. Manager interface (login)‏ • telnet into 146.231.121.88 on port 5038 • Login • Action: Login • Username: voipuser • Secret: voipuser • Events: off • /r/n

  12. Manager interface (Originate)‏ • Action: Originate • Channel: SIP/1000 • Exten: s • Context: mtsietsi • Priority: 1 • Timeout: 10000

  13. Manager interface (Monitor)‏ • Action: Monitor • Channel: SIP/ab5s51182s • File: monitor • Mix: 1

  14. Today's Practical • 1) Extend your calculator to incorporate an AGI program • Do the calculation • Parse the numbers • Take a number to a power • Solve complex problems i.e. y = ax4 + ax3 = ax2 + ax + a

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