There are a number of ways to upload and download files to and from the actual ESX server in my environment. The least favourite one I have would have to be browsing the datastore via VI Client!
This is the sort of problem that can happen, especially if you’re trying to download a file from a running Virtual Machine.
The error that appears is a:
Expected put message. Got: ERROR
The problem here is file locks. Old log files (no longer in use) will have no locks on them, so can be downloaded. Files like the vswp (Virtual Machine Swap) will be in constant use by the virtual machine and so cannot have the locks brokent to allow them to be downloaded.
The simple solution is to turn off a vritual machine before downloading the files relating to it.