RFC 959 permits the server to send a mark before its greeting:
120 Give me 37 seconds... 220 Features: p .However, servers must not do this. The BSD ftp program will treat the 120 as if it were a 220, causing a disastrous loss of synchronization with the server.
220 Features: p .RFC 959 does not impose any requirements on the text after 220. Most servers use the text for a human-readable operating system name. Some servers use multiple-line responses for human-readable announcements:
220-See ir.html if you're looking for IR information. 220-See index.html for everything else. 220- 220 Features: a p .
The string 220 Features: on the last line of the greeting indicates an experimental greeting format, designed to help speed up clients. The rest of the line is a series of feature strings, in any order, each preceded by one space, terminated by a space and a dot at the end of the line.
Feature strings do not contain spaces. Feature strings have the general format xy, where x is one of the following strings:
Note that greeting lines are case-sensitive: servers must use lowercase and uppercase exactly as shown here.
421-ftp.heaven.af.mil is too busy to provide files right now. 421 Please come back in 2040 seconds.The server closes the connection without reading any requests from the client.