In cmd prompt i tried ftp ftp.(Computer Name)that is local area network but it shows unknown host name error.
This is a DNS lookup issue - you shouldn't prefix with "ftp."
Just run "ftp computername".
You can also test this by trying to ping the machine in question: "ping ftp.computername" will fail to resolve (with a slightly more meaningful message than the FTP client gives), whereas "ping computername" will respond to ping (unless security software is preventing this).