The server rejected SFTP connection, but it listens for FTP connections.

Full message is:

The message is always associated with one of the following errors:

• Server unexpectedly closed network connection;
• Network error: Connection refused;
• Network error: Connection reset by peer;
• Network error: Connection timed out.

WinSCP uses SFTP protocol by default, contrary to most other file transfer clients, which use FTP protocol.

For this reason, when you try to connect using the default SFTP protocol to a server that does not have SSH/SFTP service (does not have port 22 open), but it has FTP service (port 21 open), it suggests you that you might have actually wanted to use FTP.

You need to select FTP protocol explicitly on Login dialog.