Remember that a war file is only a jar file with a specific internal layout, and that a jar file is just a zip file with a manifest and a different filetype.
I suggest that you first try expanding your created jar to a temporary area using WinZip or a similar tool to see what's actually in it. Don't rely on the cryptic messages from the server.
I also suggest that the
Ant "war" task (despite its name) is not a good choice for general purpose construction of web applications. the "war" task is designed for gathering together widely separated application components. If you have control over where the bits of your application are built, it's usually much better to assemble the web application directory structure in a "build directory" somewhere, then use the simpler "jar" task to build the war archive from everything in that directory.
I describe this approach in more detail in
part 4 of my "small and simple web applications" article series in the
JavaRanch journal.
Let us know how you get on.