Java Socket Programming

Can any one suggest me how to implement the following using socket programming?

I have to implement Parallel File transfer using Socket Programming of Java.
Basically client will ask for a file transfer (download) to server (call it as server1) and the server(Server1) will contact some other server(Server 2) and both of them will transfer the file to client. Half from server1 and half from server2. And this transfer should happen parallely. At Client side we have to merge the two files in proper order.

Thanks

How will the second server connect to the client? Will the client use a ServerSocket for the second server to connect to or will the client connect to the second server?