[wp-hackers] Update of own plugin

[Johannes Simons]

Hello,
I've written a WordPress-Plugin and I'd like to add the function, it can 
be updated by the user in the Admin-Panel. Also the user should get an 
advice, if a new version is online.
Now I have that value "Update Server" in the Plugin-paramters with an 
URL to my website.
My question is: What do I have to put on the "Update Server", so that 
updating in the Admin-Panel becomes possible?

No one in the wordpress.org Forum could help me... Maybe you can?!

Thank you!!

Johannes