# Stem Docs

## The Little Relay that Could

Let’s say you just set up your very first Tor relay (thank you!), and now you want to write a script that tells you how much it is being used.

First, for any script to talk with your relay it will need to have a control port available. This is a port that’s usually only available on localhost and protected by either a password or authentication cookie.

Look at your torrc for the following configuration options…

    # This provides a port for our script to talk with. If you set this then be
    # sure to also set either CookieAuthentication *or* HashedControlPassword!
    #
    # You could also use ControlSocket instead of ControlPort, which provides a
    # file based socket. You don't need to have authentication if you use
    # ControlSocket. For this example however we'll use a port.

    ControlPort 9051

    # Setting this will make Tor write an authentication cookie. Anything with
    # permission to read this file can connect to Tor. If you're going to run
    # your script with the same user or permission group as Tor then this is the
    # easiest method of authentication to use.

    CookieAuthentication 1

    # Alternatively we can authenticate with a password. To set a password first
    # get its hash...
    #
    # % tor --hash-password "my_password"
    # 16:E600ADC1B52C80BB6022A0E999A7734571A451EB6AE50FED489B72E3DF
    #
    # ... and use that for the HashedControlPassword in your torrc.

    HashedControlPassword 16:E600ADC1B52C80BB6022A0E999A7734571A451EB6AE50FED489B72E3DF

When you change your torrc you’ll need to either restart Tor or issue a SIGHUP for the new settings to take effect. Now let’s write a script that tells us how many bytes Tor has sent and received since it started. Note that there are a few ways to connect to Tor. If you’re unfamiliar with the ‘with’ keyword then see here…

    from stem.control import Controller

    with Controller.from_port(port = 9051) as controller:
      controller.authenticate()  # provide the password here if you set one

      bytes_read = controller.get_info("traffic/read")
      bytes_written = controller.get_info("traffic/written")

      print("My Tor relay has read %s bytes and written %s." % (bytes_read, bytes_written))

    % python example.py
    My Tor relay has read 33406 bytes and written 29649.

Congratulations! You’ve just written your first controller script.