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192 lines
7.4 KiB
192 lines
7.4 KiB
Asterisk External IVR Interface
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-------------------------------
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If you load app_externalivr.so in your Asterisk instance, you will
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have an ExternalIVR() application available in your dialplan. This
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application implements a simple protocol for bidirectional
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communication with an external process, while simultaneous playing
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audio files to the connected channel (without interruption or
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blocking).
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There are two ways to use ExternalIVR(); you can execute an
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application on the local system or you can establish a socket
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connection to a TCP/IP socket server.
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To execute a local application use the form:
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ExternalIVR(/full/path/to/applcation[(arguments)],options)
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The arguments are optional, however if they exist they must be
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enclosed in parentheses. The external application will be executed
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in a child process, with its standard file handles connected to the
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Asterisk process as follows:
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stdin (0) - events will be received on this handle
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stdout (1) - commands can be sent on this handle
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stderr (2) - messages can be sent on this handle
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* Use of stderr for message communication is discouraged because
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it is not supported by a socket connection.
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To create a socket connection use the form:
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ExternalIVR(ivr://host[:port][(arguments)],options)
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The host can be a fqdn or an ip address. The port is optional, if
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not specified the default of 2949 will be used. The arguments are
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optional however if they exist they must be enclosed in parentheses.
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TheExternalIVR application will connect to the specified socket
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server and establish a bi-directional socket connection, where
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events will be sent to the TCP/IP server and commands received
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from it.
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The specific ExternalIVR options, events and commands are detailed
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below.
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Upon execution, if not specifically prevented by an option, the
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ExternalIVR application will answer the channel (if it's not
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already answered), create an audio generator, and start playing
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silence. When your application wants to send audio to the channel,
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it can send a command (see below) to add a file to the generator's
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playlist. The generator will then work its way through the list,
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playing each file in turn until it either runs out of files to
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play, the channel is hung up, or a command is received to clear
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the list and start with a new file. At any time, more files can
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be added to the list and the generator will play them in sequence.
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While the generator is playing audio (or silence), any DTMF events
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received on the channel will be sent to the child process (see
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below). Note that this can happen at any time, since the generator,
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the child process and the channel thread are all executing
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independently. It is very important that your external application
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be ready to receive events from Asterisk at all times (without
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blocking), or you could cause the channel to become non-responsive.
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If the child process dies, or the remote server disconnects,
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ExternalIVR() will notice this and hang up the channel
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immediately (and also send a message to the log).
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ExternalIVR() Options
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---------------------
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n: 'n'oanswer, don't answer an otherwise unanswered channel.
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i: 'i'gnore_hangup, instead of sending an 'H' event and exiting
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ExternalIVR() upon channel hangup, it instead sends an 'I'
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event and expects the external application to exit the process.
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d: 'd'ead, allows the operation of ExternalIVR() on channels that
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have already been hung up.
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Events
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------
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All events are be newline-terminated strings and are sent in the
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following format:
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tag,timestamp[,data]
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The tag can be one of the following characters:
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0-9: DTMF event for keys 0 through 9
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A-D: DTMF event for keys A through D
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*: DTMF event for key *
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#: DTMF event for key #
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H: the channel was hung up by the connected party
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E: the script requested an exit
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Z: the previous command was unable to be executed. There may be a
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data element if appropriate, see specific commands below for
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details
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T: the play list was interrupted (see S command below)
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D: a file was dropped from the play list due to interruption (the
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data element will be the dropped file name) NOTE: this tag
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conflicts with the D DTMF event tag. The existence of the data
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element is used to differentiate between the two cases
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F: a file has finished playing (the data element will be the file
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name)
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P: a response to the 'P' command (see below)
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G: a response to the 'G' command (see below)
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I: a Inform message, meant to "inform" the client that something
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has occurred. (see Inform Messages below)
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The timestamp will be 10 digits long, and will be a decimal
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representation of a standard Unix epoch-based timestamp.
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Commands
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--------
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All commands are newline-terminated strings.
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The child process can send one of the following commands:
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S,filename
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A,filename
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H,message
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E,message
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O,option
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V,name=value[,name=value[,name=value]]
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G,name[,name[,name]]
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L,log_message
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P,TIMESTAMP
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T,TIMESTAMP
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The 'S' command checks to see if there is a playable audio file with
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the specified name, and if so, clear's the generator's playlist and
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places the file onto the list. Note that the playability check does
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not take into account transcoding requirements, so it is possible for
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the file to not be played even though it was found. If the file does
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not exist it sends a Z response with the data element set to the file
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requested. If the generator is not currently playing silence, then T
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and D events will be sent to signal the playlist interruption and
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notify it of the files that will not be played.
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The 'A' command checks to see if there is a playable audio file with
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the specified name, and if so, appends it to the generator's playlist.
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The same playability and exception rules apply as for the 'S' command.
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The 'E' command logs the supplied message to the Asterisk log, stops
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the generator and terminates the ExternalIVR application, but continues
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execution in the dialplan.
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The 'H' command logs the supplied message to the Asterisk log, stops
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the generator, hangs up the channel and terminates the ExternalIVR
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application.
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The 'O' command allows the child to set/clear options in the
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ExternalIVR() application.
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The supported options are:
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(no)autoclear: Automatically interrupt and clear the playlist
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upon reception of DTMF input.
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The 'T' command will answer an unanswered channel. If it fails either
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answering the channel or starting the generator it sends a Z response
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of "Z,TIMESTAMP,ANSWER_FAILED" or "Z,TIMESTAMP,GENERATOR_FAILED"
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respectively.
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The 'V' command sets the specified channel variable(s) to the specified
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value(s).
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The 'G' command gets the specified channel variable(s). Multiple
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variables are separated by commas. Response is in name=value format.
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The 'P' command gets the parameters passed into ExternalIVR() minus
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the options to ExternalIVR() itself:
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If ExternalIVR() is executed as:
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ExternalIVR(/usr/bin/foo(arg1,arg2),n)
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The response to the 'P' command would be:
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P,TIMESTAMP,/usr/bin/foo,arg1,arg2
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NOTE: This is the only way for a TCP/IP server to be able to get retrieve
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the arguments.
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The 'L' command puts a message into the Asterisk log. NOTE: This is
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prefered to using stderr and is the only way for a TCP/IP server to
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log a message.
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Inform Messages
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---------------
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The only inform message that currently exists is a HANGUP message,
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in the form I,TIMESTAMP,HANGUP and is used to inform of a hangup
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when the i option is specified.
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Errors
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------
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Any newline-terminated output generated by the child process on its
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stderr handle will be copied into the Asterisk log.
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