If you are getting an error message like “Connection refused”, “Connection timed out” or “Can’t resolve host name”, it is likely that there is a local firewall set up with per-application rules. The rules may allow the other clients, but not WinSCP.

You may also start getting the error after upgrading WinSCP. Some firewalls check executable file fingerprint. As the executable file changes with upgrade, the firewall starts blocking the executable, although you may have added exception rule for WinSCP already.

On Windows XP SP2 and newer, there is a built-in firewall. To configure its rules go to Start > Settings > Control Panel > Windows Firewall > Exceptions. There you can add an exception for winscp.exe.

For other reasons of getting refused to connect, please read documentation.