VS 2010 - Client Side Authorization In Web Project

I am developing a server-client program in which server will be showing datas sent by client across a network. Without Authentication it works fine but once i give authentication i am not able to get datas from client.client is a winfrom application.i know that client must be given authorization to put data into server.

I am developing based on the link given : [URL] ....

posting server side authentication code

Code:
<authentication mode="Forms">
<forms loginUrl="Login.aspx" name=".ASPXFORMSAUTH">
</forms>
</authentication>

[Code] ....

I have written validation code also.everything works fine on the server side but not able to get data from client side..

client program is written in c#,client-server communication is via http post. Code below is how client register with the server.

private void Register()
{
// Register with the server.
RegisterMessage registerMessage = new RegisterMessage
{
ComputerName = Environment.MachineName,

[Code] .....

request to server is done based on the link below.