Generally speaking, some of the most frustrating problems to solve are those where the software tries to hide the actual error messages and explain the problem in "layman terms" so the "user won't get confused". Yes, Microsoft, I'm looking at you. The result is the same every single time; the actual meaning of the original error message is lost and the end user has no way of discerning exactly why he's getting some misleading message about "the PC is powered off" (because it actually isn't) or "the ethernet port is disabled" (no, it's not).

If at all possible, relay whatever error message the module or operating system returns in verbatim to the user and then optionally ADD hints for well known error messages. Include enough information to actually troubleshoot the problem, such as the IP address and port number. Perhaps the port is blocked by a firewall? Someone typed the IP address wrong in a config file?

Good:

No route to host
Hint: Is the FOOBAR server running?
[download]

Better:

Unexpected error connecting to #.#.#.# tcp/#: No route to host
Hint: Is the FOOBAR server running?
[download]

Bad:
Error 111

Infuriating:
Server PC down