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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html><head> <title></title></head><body><a href="index.html">back to the ToC</a><h2>The concept of "External Applications"</h2>KPhone SI uses the concept "External Application" to start applicationsfor communication on both ends of the call. A good example is KPhoneIM,a simple point-to-point IM application,other examples are the MICE tools of the project MBONE such as vic andwbd (whiteboard). Those applications are triggered by an INVITEtransaction with a specfic SDP-description, as describee below. KPhoneSI itself supports STUN for NAT traversal. It may be used for allmedia tools. External Applications may make use of it, if they supportsymmetric signalling. KPhoneIM does this and so mayserve as an example for further apps. The MICE tools, originallydesigned for multicast do not, but is is possible to adaptthem.<h3>The SDP-Description </h3>RFC 2327 proposes the type m=application, for non audio and non videosessions. The parameter format must be defined per case. Thus we definethe format for generalized sessions: <br><b><i>m=application <port> <transport> <fmt></i></b><br>transport may be UDP or RTP/AVP<br>fmt is set to the session's "VectorId". We use imp2p for point to pointIM.<br>To denote applications "remote startable the tag<br><b><i> a=fmtp:<fmt> rstart</i></b><br>is added.<h3>Preparing the SDP-Parameters: Initialization by Session Table andVectorID</h3>The KPhone SI has four entries for external sessions. It is up totheuser to initialize them. The Vector-ID defines the session type. Onlyif both peers use the same,the session will be accepted, otherwise the call is rejected.<br><br>Per session template the following information can by specified byconfiguration:<ul> <li>The executable </li> <li>The command line </li> <li>The sessions icon to be shown in the main panel </li> <li>The control button for remote start </li> <li>The VectorId </li> <li>The button field for Hold Allowed </li> <li>The button field for Transfer Allowed </li> <li>Use Sound Card (to prevent the start of other calls of thattype) </li> <li>The button field for SDP Transport (entries UDP and RTP)</li></ul>You find a more detailed explanation about the configuration of aexternal application in the chapter <a href="usermanual3.html#ct">Howto configure the phone</a><br><h3>The Application</h3>Between KPhone SI and the application no communication isimplemented.Therefore all information, the application needs, <b>must</b> betransfered in thecommandline. To support this KPhone SI offers a set of variables, whichmay be used to compose the command line.They are substituted by the phone:<br> <br><b>%A</b> IP address of the peer <br><b>%P</b> media port of the peer <br><b>%O</b> own media port <br><b>%I</b> direction flag equals to <b>o</b> for an outgoing to <b>i </b>foran incoming call<br><b>%T</b> selected transport media ,0 = UDP, 1 = RTP/AVP <br><b>%D</b> the Call-ID <br><b>%M</b> the own URI <br><b>%C</b> the partner URI <br><b>%L </b>the own IP-address <br><b>%R</b> the referto-URI<br><br><a href="index.html">back to the ToC</a><br></body></html>⌨️ 快捷键说明
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