This question is FAR to broad to answer :D . Clients are not just made in a day or so, nor are they easy to build.

Since all the code is open source, you could check how the web client was built, or perhaps even check the code behind the older (deprecated) GTK client?

I understand what you mean, but i want to change the client interface, because only i need some functionality.where i can found the directory of client source code?any guide to show me how to modificate the client side?thank you Ludo.