Difference Between AppleScript Version and AppleScript Studio Version

Try this

tell application "Firefox"
    activate
    tell application "System Events"
        keystroke tab
        keystroke (key code 125)
        keystroke (key code 125)
        keystroke (key code 125)        
    end tell
end tell

You might not need to activate Firefox if it's the current active app. Them you just need :

tell application "System Events"
    keystroke tab
    keystroke (key code 125)
    keystroke (key code 125)
    keystroke (key code 125)        
end tell

This works as a shell test, if you replace with your target.

echo "QUIT" | telnet <host> ftp 2>&1 | grep  "Escape character is" > /dev/null

We're using hardly any complex tools, we just send a command to the server that makes it close our connection. If this works, the ftp-server is up and running. If we couldn't connect at all, this line returns 1, else it returns 0.

Digested to an AppleScript it's something like

set hostn to <host>
try
    do shell script "echo \"QUIT\" | telnet " & hostn & " ftp 2>&1 | grep  \"Escape character is\" > /dev/null"
    display dialog "Online."
on error
    display dialog "Not online."
end try