Ubuntu Servers :: How To Edit The File Ports.conf

I want to edit the file ports.conf to make Apache to listen only to loopback interface as described [URL]... here ,The text extract follows

Quote:

The Listen directive specifies the port, and optionally the IP address, Apache2 should listen on. If the IP address is not specified,Apache2 will listen on all IP addresses assigned to the machine it runs on. The default value for the Listen directive is 80. Change this to 127.0.0.1:80 to cause Apache2 to listen only on your loopback interface so that it will not be available to the Internet, to (for example) 81 to change the port that it listens on, or leave it as is for normal operation. This directive can be found and changed in its own file, /etc/apache2/ports.conf

But by typing [CODE]sudo vi /etc/apache2/ports.conf [/CODE} and opening the file I am not able to edit the file After going to the Listen Directive I am not able to type 127.0..0.1, Since what I type does not appear on the screen, the Keyboard is not working. How will I be able to edit the ports.conf and other configuration files