well the error message you have posted contains TWO suggestions on what to do, and both seem like very good advice. You do not state in any way that you do not understand these lines or such like.
basically 127.0.0.1 is a loopback interface, i.e. the internal network address. it should not have a name as such as it is not on a LAN. you should set the details in /etc/hosts to define the hostname as that of the external IP, just as that text tells you to.