Suggestions on keeping connections alive with FTP file listing via AJAX?

I have a multi-user Ruby on Rails web application that can interact with an FTP server via AJAX. The application allows the user to browse an FTP site. Ja开发者_StackOverflow社区vascript makes an AJAX call which communicates with a server-script that returns a list of files and directories within a given directory.

This works fine. However, each time a directory listing is requested, the server must re-establish a connection with the FTP server, which takes a lot of time. I'm looking for a way to leave the FTP connection open for until some number of timeout seconds.

I could probably do this using threads (though, I'm completely open to other ideas) or some fancy connection-pooling scheme (perhaps via a daemon that manages this).

What are some ways I could persist and regain reference to connections in my ruby source?

Someone suggested using a "Connection: Keep-Alive" header, but I don't see how that would help in this case.

Not a complete answer, but if you did have some sort of daemon or something managing the connection, you could use TCP keepalives to keep the control connection alive for an extended period of time.

FTP uses two connections. A control connection is established client-to-server, and data connections are established server-to-client for each request. So each directory listing or GET would prompt another data connection to be opened for the duration of the request.

You shouldn't worry about keeping lots of listening sockets open because the data connections are negotiated over the control connection just prior to being established. (Also the data connections could be made client-to-server instead of server-to-client by using passive mode if you want, but it's still a separate connection.)

Either way, I think the source of sluggishness is more to do with closing and reopening the control connection (and authenticating) for each request. I think if you have some process that keeps the control connection open using TCP keepalives (SO_KEEPALIVE socket option), you'll see a big improvement.