I assume you are using ethernet since you are using FTP. Have you tried doing this with either serial or USB while using emplode?

Have you tried using jEmplode over the same links?

Which host OS are you using?

Do you have a firewall or router with packet management features that silently drops packets of LAN traffic?

Can you examine inside of the ethernet socket and check for bent, damaged or crossed wires? (...and before the entire community jumps in here, I would like it to be checked to eliminate it as a fault - even if ethernet DOES appear to be working OK).