Are you using hftp:// or webhdfs://? I'd recommend trying with the latter.

For this specific exception in REST based copies, its usually not a fault with the network but a buggy state in the older Jetty used on the source cluster. Typically a rolling restart of the DataNodes will help resolve such a bad state of Jetty where it hangs up on a client mid-way during a response, causing the sudden EOF to the copying client in DistCp when it was expecting the rest of data.