#!/usr/bin/expect
set timeout 20
set ip [lindex $argv 0]
set port [lindex $argv 1]
set user [lindex $argv 2]
set password [lindex $argv 3]
 
spawn telnet $ip $port
expect "'^]'."
sleep .1;
send "\r";
expect
{
  "login:"
  {
        send "$user\r"
        expect "Password:"
        send "$password\r";
        interact
 
  }
 
  "host: Connection refused"
  {
    send_user "ERROR:EXITING!"
    exit
  }
 
}

http://stackoverflow.com/questions/7789710/expect-script-to-automate-telnet-login