developing FTP client

There are a number of open source ftp clients; you can just get them and read their code. The Linux command-line ftp client would be a start; being command line might make it somewhat simpler in structure.

I don't quite understand why you want an FTP client, though, as FTP is fairly insecure, both from a cleartext password perspective, and from a port spoofing perspective. If you need to upload data over the web, I'd try to support HTTP POST with the option of running over HTTPS instead.

As you'll probably realise, FTP is a really crappy protocol.

It's crappy because it uses two sockets at once. Their data are related, but they are separate sockets. This leads to all sorts of problems with firewalls. It also historically caused security problems (i.e. "bounce" attacks).

If it's some part of another program, I recommend using another protocol. Hey, even TFTP doesn't have that problem (although it has its own problems, i.e. using UDP in a simplistic way makes for terrible performance).

Mark

I've programmed an FTP server in java and I found this site helpful. The RFC (959) is quite old and that site gives you some pointers on what you should ignore or add.

This FTP Client is to be used over a secure Cisco VPN connection.

Already support HTTP POST, this project requires FTP Client as customer is using
FTP Server.

Thanks
Cubex

Your biggest problem will probably be the poor UNIX era RPC of the text based "protocol". Specifically if you plan any kind of GUI interface, you'll need to write a parser that attempts to figure out what format directory listings are sent in and parse them. If the client only has to work with one FTP server this won't be a problem. If it's a general purpose client, you'll have lots of fun figuring out why it doesn't work with FTP Server XYZ.

Thanks for the headsup Michalson

Thanks all
CubeX