Symptom: A Restore/Replicate job fails with the error: 

"XenServer dropped the connection (I/O)" 

or 

"Unable to write data to the transport connection: An existing connection was forcibly closed by the remote host."

Unfortunately, in certain cases, XenServer does not return an explanation of why there was a failure.  Generally, these errors occur due to problems with the selection or configuration of the target XenServer's Storage Repository.  Common solutions to this problem have been:

-Selecting a default Storage Repository for your XenServer

-Ensuring the target Storage Repository is not read-only

-Ensuring the target Storage Repository is visible to the target XenServer (eg. not "unplugged")

To determine the exact cause of this failure, you must look at the XenServer's xensource.log file.  This can generally be found in /var/log/ of the target XenServer.