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<concept id="GUID-768CCC6E-16D2-50E8-8EED-EB2C2AF0E9BE" xml:lang="en"><title>Overview</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>The SIP Client Resolver defines the architecture used to resolve or identify

the target client when SIP requests are received from the default port. The

Symbian SIP stack is implemented as a Symbian server and uses the default

UDP and TCP port 5060 to send and receive SIP messages. Many applications

or target clients receive SIP messages that use the default port, and the

correct target client must be determined. </p>

<p>The SIP Client Resolver determines the target client based on the SIP request

and the XML-description provided by every SIP Client Resolver API implementation.

It requests the resolved ECOM plug-in to connect to the SIP or another server

which uses SIP. </p>

<section><title>Architectural relationships</title> <p>The Client Resolver

API requires the SIP Codec API and the SIP Codec API. </p> <p>The target clients

that receive SIP requests must implement the API Client Resolver API. The

following are the two methods in which a target client can receive SIP requests: </p> <ul>

<li id="GUID-F3BEAD9E-744E-5154-91EC-E0B66034A8F4"><p> <b>Implement the CSIPResolvedClient

interface and provide an XML description with their capabilities</b>  </p> <p>The

XML description describes the supported content-types and media formats that

use SIP headers and SDP m-lines in the ECOM resource file. Client Resolver

framework determines the target client by comparing the incoming SIP request

to the XML descriptions provided by the <xref href="GUID-F0E4FA44-A41C-3C6F-993E-39CED042A879.dita"><apiname>CSIPResolvedClient</apiname></xref> implementation. </p> </li>

<li id="GUID-07B5DFE5-D376-57F7-8ACB-50BB1EF8351B"><p>Implement the <xref href="GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E.dita"><apiname>CSIPResolvedClient2</apiname></xref> interface

and add Request-URIs user-part, plug-ins UID, and the client UID to the SIP

Client Resolver mapping table in the Central Repository </p> <p>The table

maps the user-part of the incoming SIP request’s Request-URI to the related <xref href="GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E.dita"><apiname>CSIPResolvedClient2</apiname></xref> implementation’s

UID. SIP Client Resolver framework gives the SIP request to only the plug-ins

for which a mapping entry is found in the Central Repository. </p> </li>

</ul> <p>This implies that every target client must provide an ECOM plug-in

that is used by the Client Resolver Framework. The Client Resolver Framework

uses the information in the SIP request and matches it with the XML description

or the mapping table entry provided by the target clients. It then decides

which target client plug-in to load. </p> </section>

<section><title>Class structure</title> <p>SIP Client Resolver must create

a class derived from <xref href="GUID-F0E4FA44-A41C-3C6F-993E-39CED042A879.dita"><apiname>CSIPResolvedClient</apiname></xref> or <xref href="GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E.dita"><apiname>CSIPResolvedClient2</apiname></xref> to

receive requests outside the SIP dialogs. If the target client is not running,

it must be started to enable it to receive SIP requests. </p> <fig id="GUID-B8A796EA-6850-5695-A516-E92629BE7971">

</fig> <p><b>CSIPResolvedClient</b> </p> <p>The target clients must implement

the <xref href="GUID-F0E4FA44-A41C-3C6F-993E-39CED042A879.dita"><apiname>CSIPResolvedClient</apiname></xref> interface to receive SIP requests

outside SIP dialogs and enable the client resolution mechanism. </p> <p>SIP

uses the data provided in the ECOM resource file or, as requested by the implementation

to decide which target client is used. </p> <p><b>CSIPResolvedClient2</b> </p> <p>The

target clients must implement the <xref href="GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E.dita"><apiname>CSIPResolvedClient2</apiname></xref> interface

to receive SIP requests outside SIP dialogs and enable the client resolution

mechanism. </p> <p>The SIP stack uses the plug-ins that implement this interface

as follows: </p> <ol id="GUID-E3325143-0AA4-5A60-885C-875F388EF0E3">

<li id="GUID-816770B7-3A85-5894-9868-64BEE12FD50C"><p>If the SIP request does

not contain the Accept-Contact-header, go to step 2. If it does, the SIP stack

calls the <xref href="GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E.dita#GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E/GUID-2C145D8C-DB4C-33C9-9CCE-193433909937"><apiname>CSIPResolvedClient2::MatchAcceptContactsL()</apiname></xref> method

on all the plug-ins and applies the following logic: </p> <ul>

<li id="GUID-5457D39D-DE84-5A3F-8E8B-7E79C863E118"><p>If none of the clients

match, go to step 2. </p> </li>

<li id="GUID-BE1A9D22-BD88-519E-AC4A-242FC6D3B098"><p>If one of the clients

match, send the SIP request to the matching client. </p> </li>

<li id="GUID-3A027E2A-C805-595D-B43C-28B19BC07609"><p>If more than one of

the clients match, go to step 2. </p> </li>

</ul> </li>

<li id="GUID-7F822965-0220-52A8-8CAF-EACA4D87E75D"><p>If the SIP request does

not contain the Event-header, go to step 3. If it does, SIP stack calls the <xref href="GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E.dita#GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E/GUID-9DB2CFFE-09ED-367D-9C14-6917F8E3DCF4"><apiname>CSIPResolvedClient2::MatchEventL()</apiname></xref> method

on all the plug-ins and applies the following logic: </p> <ul>

<li id="GUID-8E85F9F9-D645-53D7-A4D8-6717951B0D1C"><p>If none of the clients

match, go to step 3. </p> </li>

<li id="GUID-B713BE42-D8AF-51D6-8832-D0B221CFF4D8"><p>If one of the clients

match, send the SIP request to the matching client. </p> </li>

<li id="GUID-93037264-2B67-5DD4-990B-9D3EEEDE6C4D"><p>If more than one of

the clients match, go to step 3. </p> </li>

</ul> </li>

<li id="GUID-BFCEF7B8-4068-58E6-B960-27035A5A52D6"><p>The SIP stack calls

the <xref href="GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E.dita#GUID-30BC7BC4-0FBE-3C60-A2E4-2E5AE206C61E/GUID-9C9E49C8-602B-3C1C-B036-A176FF323A54"><apiname>CSIPResolvedClient2::MatchRequestL()</apiname></xref> method on all

the plug-ins and applies the following logic: </p> <ul>

<li id="GUID-86228E63-7E10-571E-B465-EB4D14E8855D"><p>If none of the clients

match, an error response is generated. </p> </li>

<li id="GUID-6F578483-34E7-5CFB-A565-2209FFF82D28"><p>If one of the clients

matches, send the SIP request to the matching client. </p> </li>

<li id="GUID-C1BD2E18-CFEB-558F-9F10-60EF6B9539E7"><p>If more than one of

the clients match, one of the client is randomly selected and the SIP request

is sent to it. Normally, the ROM-based clients are preferred. </p> </li>

</ul> </li>

</ol><p>The channel UIDs must be unique across all SIP clients. The clients

may use UIDs assigned for the binaries. </p> </section>

</conbody><related-links>

<link href="GUID-5C215C64-5D3D-5B65-A11F-BE6F8C306CF4.dita"><linktext>How     

           the target client is resolved using CSIPResolvedClient</linktext>

</link>

<link href="GUID-AFE7F3DA-6D61-5A4C-A08F-C998C8805A06.dita"><linktext>How     

           the target client is resolved using CSIPResolvedClient2</linktext>

</link>

</related-links></concept>