Smack File Transfer Problem

Hi,

I have a question regarding to the file transfer.

In my program, I created User A and User B.

A was sending the file to B.

My original code was like this:

// Create the outgoing file transfer
        OutgoingFileTransfer transfer = manager.createOutgoingFileTransfer("xxxxxx@gmail.com");

but it didn't work, the smack debuger said Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: IQ Type not understood

But i chaged to

       OutgoingFileTransfer transfer = manager.createOutgoingFileTransfer("xxxxxx@gmail.com/Smack05B73129");

and it worked...

Can anyone know why createOutgoingFileTransfer requires that weird receiver userID? Is there any way make the first way work?

Thank you.