This article provides brief information and a recommendation to resolve the following error when transferring a file in TFTP Server:
All Engineer's Toolset versions
This error is typically caused by a firewall blocking access.
We recommend disabling any firewalls on the machine running the TFTP Server.
FYI, Cisco's VPN client has a setting under options that states "Stateful Firewall Always On". If you have this client installed, you will want to uncheck this setting.