Close Data connection prior to reading 2XX response?

Hi there,

I've learned a lot about FTP and Go through reading your code, the spec and troubleshooting issues on a specific FTP server. This particular server expects the client to close the data connection before it will issue the 2XX message on the control connection.

I am still not sure if this is expected behavior after reading and re-reading the spec (http://www.ietf.org/rfc/rfc959.txt), but it seems as if other FTP clients/libraries tend to close the data connection before reading from the control connection again:

https://github.com/ruby/ruby/blob/trunk/lib/net/ftp.rb#L487
http://sources.debian.net/src/netkit-ftp/0.17-30/ftp/ftp.c#L1249

What do you think? It seems as if the tinyftp library could be refactored to automatically create and close the passive connection in `List()`, `NameList()`, `Retrieve()`, and `RetriveTo()`. If you agree, I could take a first pass.

Thank you!