Part 1: Intro, Part 2: Tropo/PHP, Part 3: Asterisk Manager/Perl

These notes are from a weekend of hacking and debugging with Michigan Telephone, the first guinea pig to try out the “analog remix” scripts. Thanks for the extra challenges. 🙂

Asterisk 1.4, 1.8 and the Asterisk Manager Interface

• Asterisk 1.4’s Manager calls the channel that is bridged to the current channel “Link.” Newer versions, more sensibly, call it “BridgedChannel.” I updated the Perl CGI to use whichever is defined, so now the CGI will work with newer versions of Asterisk, and not just 1.4.
• A bug exists on specific versions of Asterisk 1.4, 1.6 and 1.8 that breaks call transfer from the Manager (as well as SIP blind transfers). The current -rc1 versions, as of this writing, have the fix: 1.4.39-rc1, 1.6.2.16-rc1, and 1.8.2-rc1. This bug has been in 1.4 since 1.4.38-rc1; in 1.6 since 1.6.2.15-rc1; and in 1.8 since 1.8.0-rc4. If you’re on a buggy version, the transfer will just hang up the channel.
• How to set up the Manager user may not be obvious. Just make a new user block in manager.conf or manager_custom.conf (FreePBX) with the following permissions:

  [tropousername]
secret = tropopassword
deny=0.0.0.0/0.0.0.0
permit=127.0.0.1/255.255.255.0
read = call
write = call

  Set the username and password to whatever you want, and then use these in the Perl CGI in the AMI::Common::new() function. Your manager user needs only “call” permissions to perform the actions in the CGI.

Perl

• MT notes that you may have to install the AnyEvent and parent Perl modules before Asterisk::AMI. Use CPAN’s installer if you can: perl -MCPAN -e shell and install parent, AnyEvent, and Asterisk::AMI
• The Data::Dumper module can be really helpful if you find that things aren’t going well with your CGI. Just use Data::Dumper at the top of the CGI, then print STDERR Dumper($variablename) wherever you need it. Try this on a hash, such as $currchan, and you’ll get a dump of the whole thing.

Firewall/ACL

You may want to set up a separate Apache VirtualHost with access controls (username/password and/or IP access list) for your Tropo CGI. Or, if your web server is firewalled, you’ll need to let Tropo in to make the request. Tropo’s support team indicated that requests will come from 66.193.54.21, so this IP can be allowed through your firewall. They will announce any changes to this on changes.tropo.com.