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  <header>
    <copyright>
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      <holder>Ericsson AB. All Rights Reserved.</holder>
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      Licensed under the Apache License, Version 2.0 (the "License");
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    <title>megaco_transport</title>
    <prepared>Micael Karlberg</prepared>
    <responsible>Micael Karlberg</responsible>
    <docno></docno>
    <approved>Micael Karlberg</approved>
    <checked></checked>
    <date>2007-06-15</date>
    <rev>%VSN%</rev>
    <file>megaco_transport.xml</file>
  </header>
  <module>megaco_transport</module>
  <modulesummary>Megaco transport behaviour.</modulesummary>
  <description>
    <p>The following functions should be exported from a 
      <c><![CDATA[megaco_transport]]></c> callback module:</p>
    <list type="bulleted">
      <item>
        <p><seealso marker="#send_message">send_message/2</seealso> [<c><![CDATA[mandatory]]></c>]</p>
      </item>
      <item>
        <p><seealso marker="#send_message">send_message/3</seealso> [<c>optional</c>]</p> 
      </item>
      <item>
        <p><seealso marker="#resend_message">resend_message/2</seealso> [<c><![CDATA[optional]]></c>]</p>
      </item>
      <item>
      </item>
    </list>
    <marker id="send_message"></marker>
  </description>
  <funcs>
    <func>
      <name>Module:send_message(Handle, Msg) -> ok | {cancel, Reason} | Error</name>
      <name>Module:send_message(Handle, Msg, Resend) -> ok | {cancel, Reason} | Error</name>
      <fsummary>Send a megaco message.</fsummary>
      <type>
        <v>Handle = term()</v>
        <v>Msg = binary() | iolist()</v>
        <v>Resend = boolean()</v>
        <v>Reason = term()</v>
        <v>Error = term()</v>
      </type>
      <desc>
        <p>Send a megaco message. </p>
        <p>If the function returns <c><![CDATA[{cancel, Reason}]]></c>, 
          this means the transport module decided not to send the message. 
          This is <em>not</em> an error. No error messages will be issued 
          and no error counters incremented. 
          What actions this will result in depends on what kind of
          message was sent. 
          </p>
        <p>In the case of requests, megaco will cancel the message in much 
          the same way as if <c><![CDATA[megaco:cancel]]></c> had been called 
          (after a successfull send). The information will be propagated
          back to the user differently depending on how the request(s) where
          issued: For requests issued using 
          <seealso marker="megaco#call">megaco:call</seealso>, the info
          will be delivered in the return value. For requests issued 
          using <c><![CDATA[megaco:cast]]></c> the info will be delivered 
          via a call to the callback function 
          <seealso marker="megaco_user#trans_reply">handle_trans_reply</seealso>. </p>
        <p>In the case of reply, megaco will cancel the reply and information
          of this will be returned to the user via a call to the 
          callback function 
          <seealso marker="megaco_user#trans_ack">handle_trans_ack</seealso>. </p>

        <p>The function <c>send_message/3</c> will only be called if the 
          <seealso marker="megaco#ui_resend_indication">resend_indication</seealso>
          config option has been set to the value <c>flag</c>. The third 
          argument, <c>Resend</c> then indicates if the message send is 
          a resend or not. </p>

        <marker id="resend_message"></marker>
      </desc>
    </func>

    <func>
      <name>Module:resend_message(Handle, Msg) -> ok | {cancel, Reason} | Error</name>
      <fsummary>Re-send a megaco message.</fsummary>
      <type>
        <v>Handle = term()</v>
        <v>Msg = binary() | iolist()</v>
        <v>Reason = term()</v>
        <v>Error = term()</v>
      </type>
      <desc>
        <p>Re-send a megaco message. </p>
        <p>Note that this function will only be called if the user has set the 
          <seealso marker="megaco#ui_resend_indication">resend_indication</seealso> 
          config option to <c><![CDATA[true]]></c><em>and</em> it is in fact a message 
          resend. If not <em>both</em> of these condition's are meet, 
          <c><![CDATA[send_message]]></c> will be called. </p>
        <p>If the function returns <c><![CDATA[{cancel, Reason}]]></c>, this means the 
          transport module decided not to send the message. 
          This is <em>not</em> an error. No error messages will be issued 
          and no error counters incremented. 
          What actions this will result in depends on what kind of
          message was sent. </p>
        <p>In the case of requests, megaco will cancel the message in much 
          the same way as if <c><![CDATA[megaco:cancel]]></c> had been called 
          (after a successfull send). The information will be propagated
          back to the user differently depending on how the request(s) where
          issued: For requests issued using 
          <seealso marker="megaco#call">megaco:call</seealso>, the info
          will be delivered in the return value. For requests issued 
          using <c><![CDATA[megaco:cast]]></c> the info will be delivered via a call
          to the callback function 
          <seealso marker="megaco_user#trans_reply">handle_trans_reply</seealso>. </p>
        <p>In the case of reply, megaco will cancel the reply and information
          of this will be returned to the user via a call to the 
          callback function 
          <seealso marker="megaco_user#trans_ack">handle_trans_ack</seealso>. </p>
      </desc>
    </func>
  </funcs>

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