xtra - Use of the XML Socket Multiuser Server extension
The XML Socket Multiuser Server can be extended using special ecs libraries. Using such extensions we can, for example, send mails from the XML Socket Multiuser Server or connect to various databases, save results of measurements or connect to applications CGI, ISAPI, PHP ASP.NET etc.

How to use the extension:
1. We have to create our own ecs library or to use an already created one.
2. We copy this library to the folder xtras.
3. In the file eClever.config we add to the section socket-server / xtras name of such ecs library and name under which we will call this extension from our applications.
4. In the domains where we want to allow using of the extension we have to insert in the file eClever.config and section domain names of all the extensions to the atribute xtras, for example xtras="test1#test2".
XML request, sent by the client to the server
   <xtra [sid="10"]>
       <data name="test1" function="abc">a=20</data>
Name of the extension we are going to call. It has to be defined in eClever.config in the section socket-server / xtras and atribute name.
Name of the function to be called.
In the section data we set parameter of the function. A function can only have one parameter and it can, for example, be a chain in the XML format.
XML response of the server to the client
    <response action="xtra" errorCode="0" sid="10">
         <data name="test1" function="abc">2747</data>
Name of the called XTRA.
The called function.
In the section data the value of the function is returned. Most often this value is in the XML format again.
Error description
The extension is not allowed in the section socket-server / xtras.
The extension is not allowed in the section domain.
You don’ t have the necessary rights to use the XTRA.
En error occuring when initializing the ecs library. It can be caused by the followings, for example:
a) The atribut name that you call in section socket-server / xtras, is not defined.
b) The ecs library defined in section socket-server / xtras in the atribute file does not exists or is not placed in the XML Socket Multiuser Server root.
c) The error is caused by an internal error regarding the initialization of the ecs library.
The function you are calling is not declared in the ecs library.