a project about python udp server/client demo, run them in different computers,you can better experience the enjoyment of network programming with python

1 this is a implementation of python udp server client model, run the code respectively in different machines, and enable that the two machines
　can ping each other,to do this , you r supposed to shut down your firewalls first.

2 I run the two py file code in two machines,first, you should get to know the ip address of server machine, and replace the HOST constant
　with your own server ip, then type message firstly on client machine, then you will find that the typed message in client machine shows in
　the server window, and then the client waits for the response from server side ,then u type message in server window, u will find that message
　show in client side　,then the server side goes into waiting for the response from client side.

3 so u implement the server / client model in UDP protocol