SFTP and FTP

to use sftp you have to download/install a sftp client which you can get from openssh suit , ( openssh.org  )

This should be useful too

http://kb.indiana.edu/data/akqg.html

U haven't told me the process involved in converting the FTP program's to SFTP and also constraints in the SFTP??

to start using sftp instead of ftp you just have to install sftp client and

instead of doing a
  ftp hostname

you do a

sftp hostname

i.e in all scripts/programs you have you just need to change all 'ftp' to 'sftp'

If you script ftp via expect or so - note that sftp may not have mget, and always uses full command , i.e get, and not g, quit and not qui etc...

There's a lot of differences between FTP and SFTP behind the covers, however from a end user point of view, there's very little difference in how they work, with the exception of automating scripts.

With FTP you can use .netrc files which SFTP doesn't support (AFAIK) and with SFTP you can use keys to automate logins.