Can I use host headers to run multiple FTP sites?
No, you cannot use a Host header to distinguish FTP sites. The FTP protocol, specified by RFC 959, does not support the Host header. The Host header is specified in the HTTP RFC (2616), thus part of the HTTP protocol. HTTP and FTP are two totally different protocol, and a FTP client and server can only “talk” FTP. The only way to run multiple FTP sites (no matter what FTP server you have) is to use a unique port and IP address combination.