What are you using on the backend? Are you send this as a multipart/form-data or just as a blob of data in an HTTP request?
Typically for file uploads I use Apache Commons FileUpload, but I usually upload from web browsers rather than clients.
You may have better luck using the FileUpload library along with HTTPClients multipart post functionality.
At a gut level, I suspect that the problem is at your end vs the container itself, as the HTTP protocol stuff is pretty mature.
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