(Because I keep forgetting this and having to straighten it out again inmy own head, it's time to write down the difference between regular ftpand passive ftp).

Ftp has to transport two different things: commands (and statusresponses to them), and the actual ftp data. In a modern protocol, thesetwo things would be multiplexed together over the same TCP connection,but ftp dates from when the Internet was both a much simpler environmentand a much more limited one, so it uses separate

There is a tendency in programming to consider any spiffy new generalfeature, such as a good infinite undo system, as the way to deal withmany of your program's problems. This is often a mistake, and undo makesa good illustration of why.

(It's easy to see how this happens; you have this powerful system thatyou've invested a lot of effort into, so it's natural to apply it on asmuch as possible. And programmers really like general solutions, because