Help with Cfftp connection

Hi

I am trying to establish a ftp connection using cfftp tag

my code is

<cfftp connection = "myConnection"

    username = "abc"

    password = "xyx"

    server = "server address"

passive = "yes"

    action = "open"

    stopOnError = "Yes">

<cfoutput>#CFFTP.Succeeded#</cfoutput>

But i am getting the following error :

The cause of this exception was that: java.net.UnknownHostException:server address

kindly advice

Thanks