ftp

aria2 is a lightweight multi-protocol & multi-source, cross platform download utility operated in command-line. It supports HTTP/HTTPS, FTP, SFTP, BitTorrent and Metalink.

Knock-Knock: A Live, Multi-Protocol Honeypot Dashboard of Internet Break-in Attempts - 13 Protocols, an Extensible Framework, and a Threat-Intelligence Database Serving a Public IP Blocklist Feed

Cyberduck is a libre FTP, SFTP, WebDAV, Amazon S3, Backblaze B2, Microsoft Azure & OneDrive and OpenStack Swift file transfer client for Mac and Windows.