FTP files no content

I have setup an FTP site on an NT4 SP6 machine using IIS 4 and files traveling over broadband connection. I made used of the FTP utility on cmd prompt to upload a test file but it always comes up that it doesn’t have its content with 0 kb and message comes up “netout: connection reset by peer”

I tried using WSFTP pro with a Received error connection reset…425 Can’t open data connection….Retreive of folder listing failed.

I have open tcp port 21 in our firewall. Are there any other ports need to be opened?
What’s wrong?

Any suggestions will be highly rated =)
Thanks in advance…