Sending and receiving in XML

[palomino]

Hello Daniel. 
You can send me one example of how I can send and receive format XML and Xsd.

this is the idea
I need to communicate with a server. 
To start the communication the server sends me information with this XML structure:

Code:

<?xml version="1.0" encoding="utf-8"?>
<stuMessages xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="http://cody.glpconnect.com/XSD/StuMessage_Rev1_0.xsd" timeStamp="27/08/2009
21:00:00 GMT" messageID="56bdca48088610048fddba385e1cd5b8">
<stuMessage>
<esn>0-99990</esn>
<unixTime>1034268516</unixTime>
<gps>N</gps>
<payload length="9" source="pc" encoding="hex">0xC0560D72DA4AB2445A</payload>
</stuMessage>
</stuMessages>

I must read the message and send a response changing the  " timeStamp=" and  " messageID=".

This is the code that I have to send:

Code:

<?xml version="1.0" encoding="utf-8"?>
<stuResponseMsg xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:noNamespaceSchemaLocation="http://cody.glpconnect.com/XSD/StuResponse_Rev1_0.xsd"
deliveryTimeStamp="25/08/2009 21:00:00 GMT" correlationID="56bdca48088610048fddba385e1cd5b8">
<state>pass</state>
<stateMessage>Store OK</stateMessage>
</stuResponseMsg>

the questions are:
How can I receive a message without sending a Request?
How can I send information in XML format?
How can I read and modify  XML format?

Tk for all your help.