201 lines
9.2 KiB
HTML
201 lines
9.2 KiB
HTML
<html>
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<head>
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<title>YATE - External module</title>
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</head>
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<body>
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The work on this document is still in progress.
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Please do not use it as reference, the specifications are likely to change.
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<h1>External module command flow</h1>
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<h2>File handles used</h2>
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The external user application or script comunicates with the module trough
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several file descriptors:<br />
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0 (stdin) - Carries commands and notifications from engine to application<br />
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1 (stdout) - Carries commands and answers from application to the engine<br />
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2 (stderr) - Has the usual meaning of reporting errors and is directed to the engine's stderr or logfile<br />
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3 (optional) - Transports audio data from the engine to the application<br />
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4 (optional) - Transports audio data from the application to the engine<br />
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File descriptors 3 and 4 are open only for audio capable applications.<br />
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<h2>Format of commands and notifications</h2>
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<p>
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Words enclosed in <angle brackets> must be replaced with the proper value.<br />
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Elements in [square brackets] are optional. An ellipsis ... denotes optional
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repetition of the last element.<br />
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Every command is sent on its own newline (\n, ^J, decimal 10) delimited line.<br />
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Any value that contains special characters (ASCII code lower than 32) MUST have
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them converted to %<upcode> where <upcode> is the character with a
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numeric value equal with 64 + original ASCII code. The % character itself MUST
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be converted to a special %% representation. Characters with codes higher than 32
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(except %) SHOULD not be escaped but may be so. A %-escaped code may be received
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instead of an unescaped character anywhere except in the initial keyword or the
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delimiting colon (:) characters. Anywhere in the line except the initial keyword
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a % character not followed by a character with a numeric value higher than 64
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(40H, 0x40, '@') or another % is an error.<br />
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</p>
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<p><b>Special Keyword: Error in</b><br />
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Error in:<original><br />
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<b>Direction: Engine to application</b><br />
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The engine sends this notification as answer to a syntactically incorrect line
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it received from the application.<br />
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<original> - the original line exactly as received (not escaped or something)<br />
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The external module SHOULD NOT send anything back to Yate in response to such a
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notification as it can result in an infinite loop.<br />
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</p>
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<p><b>Keyword: %%>message</b><br />
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%%>message:<id>:<time>:<name>:<retvalue>[:<key>=<value>...]<br />
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<b>Direction: Engine to application</b><br />
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This line is sent by the engine to the application) to ask it to process a message.
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The Yate thread that dispatches the message will block until an answer is
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received (see below).<br />
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<id> - obscure unique message ID string generated by Yate<br />
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<time> - time (in seconds) the message was initially created<br />
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<name> - name of the message<br />
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<retvalue> - default textual return value of the message<br />
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<key>=<value> - enumeration of the key-value pairs of the message<br />
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</p>
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<p><b>Keyword: %%<message</b><br />
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%%<message:<id>:<processed>:[<name>]:<retvalue>[:<key>=<value>...]<br />
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<b>Direction: Application to engine</b><br />
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One such answer is required for every received message (%%>message). When
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the engine gets a line in this format it modifies the provided values back into
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the message and let it continue or stop dispatching.<br />
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<id> - same message ID string received trough %%>message<br />
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<processed> - boolean ("true" or "false") indication
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if the message has been processed or it should be passed to the next handler<br />
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<name> - new name of the message, if empty keep unchanged<br />
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<retvalue> - new textual return value of the message<br />
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<key>=<value> - new key-value pairs to set in the message; to delete
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the key-value pair provide just a key name with no equal sign or value<br />
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</p>
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<p><b>Keyword: %%>message</b><br />
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%%>message:<id>:<time>:<name>:<retvalue>[:<key>=<value>...]<br />
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<b>Direction: Application to engine</b><br />
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This line is sent by the application to the engine to ask it to process a message.
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The answer to such a message is delivered asynchronously (see below).<br />
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<id> - obscure unique message ID string generated by the application<br />
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<time> - time (in seconds) the message was initially created<br />
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<name> - name of the message<br />
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<retvalue> - default textual return value of the message<br />
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<key>=<value> - enumeration of the key-value pairs of the message<br />
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</p>
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<p><b>Keyword: %%<message</b><br />
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%%<message:<id>:<processed>:[<name>]:<retvalue>[:<key>=<value>...]<br />
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<b>Direction: Engine to application</b><br />
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One such answer is required for every message (%%>message) the application
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sent to the engine. It contains the message's return values and parameters.<br />
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<id> - same message ID string received trough %%>message<br />
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<processed> - boolean ("true" or "false") indication
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if the message has been declared processed by one of the handlers<br />
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<name> - name of the message, possibly changed<br />
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<retvalue> - textual return value of the message<br />
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<key>=<value> - key-value pairs of parameters to the message.<br />
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</p>
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<p><b>Keyword: %%>install</b><br />
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%%>install:[<priority>]:<name><br />
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<b>Direction: Application to engine</b><br />
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Always from the application to the engine, requests the installing of a message
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handler for the application that requested it<br />
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The answer to the install request is delivered asynchronously (see below).<br />
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<priority> - priority in chain, use default (100) if missing<br />
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<name> - name of the messages for that a handler should be installed<br />
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</p>
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<p><b>Keyword: %%<install</b><br />
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%%<install:<priority>:<name>:<success><br />
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<b>Direction: Engine to application</b><br />
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Confirmation from engine to the application that the handler has been installed
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properly or not.<br />
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<priority> - priority of the installed handler<br />
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<name> - name of the messages asked to handle<br />
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<success> - boolean ("true" or "false") success of operation<br />
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</p>
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<p><b>Keyword: %%>uninstall</b><br />
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%%>install:<name><br />
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<b>Direction: Application to engine</b><br />
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Always from the application to the engine, requests uninstalling a previously
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installed message handler<br />
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The answer to the uninstall request is delivered asynchronously (see below).<br />
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<name> - name of the message handler thst should be uninstalled<br />
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</p>
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<p><b>Keyword: %%<uninstall</b><br />
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%%<install:<priority>:<name>:<success><br />
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<b>Direction: Engine to application</b><br />
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Confirmation from engine to the application that the handler has been uninstalled
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properly or not.<br />
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<priority> - priority of the previously installed handler<br />
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<name> - name of the message handler asked to uninstall<br />
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<success> - boolean ("true" or "false") success of operation<br />
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</p>
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<h2>Example</h2>
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<p>
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In the example below the lines sent from application to engine are prefixed with
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A: while lines sent from engine to application are prefixed with E:<br />
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Comments are indented<br />
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</p>
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<pre>
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Application installs a handler for a "test" handler with priority 50
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A: %%>install:50:test
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Engine installs the handler and acknowledges it
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E: %%<install:50:test:true
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Application installs a handler for the "engine.timer" handler with default priority
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A: %%>install::engine.timer
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Engine installs the handler and acknowledges it
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E: %%<install:100:engine.timer:true
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Application emits a private "app.job" message; notice how the '%' and ':' characters were escaped
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A: %%>message:myapp55251:1095112794:app.job::job=cleanup:done=75%%:path=/bin%Z/usr/bin
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Engine just dispatched an "engine.timer" message
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E: %%>message:234479208:1095112795:engine.timer::time=1095112795
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Engine gets back the answer to the "app.job" message with a "Restart required" returned text value
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E: %%<message:myapp55251:true:app.job:Restart required:path=/bin%Z/usr/bin%Z/usr/local/bin
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Application ignores the timer message
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A: %%<message:234479208:false:engine.timer::time=1095112795
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Application uninstalls the "test" handler
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A: %%>uninstall:test
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Engine removes the handler and acknowledges it
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E: %%<uninstall:50:test:true
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Engine just dispatched another "engine.timer" message
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E: %%>message:234479288:1095112796:engine.timer::time=1095112796
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Application modifies the timer message but lets it flow further
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A: %%<message:234479288:false:engine.timer::time=1095112796:extra=yes
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Engine just dispatched another "engine.timer" message
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E: %%>message:234479244:1095112797:engine.timer::time=1095112797
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Application suddenly exits without acknowledging previous message.
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The engine releases the message 234479244 (as if "false" was returned) and
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uninstalls the remaining "engine.timer" handler
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</pre>
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</body>
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</html>
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