This is a test version, so it use the ip of 127.0.0.1 to communicate with each other. Then, the server and client must be put at a same merchine.

1. Run the server, 
     eg."./server".
2. Run a series of clients, 
     eg."./client YourName".
3. These command would be used when communicating:
   ADD, add a friend who has been online, 
     eg."add FriendName";
   DEL, delete a friend, 
     eg."del FriendName";
   SAY, say to a friend who you have added, 
     eg."say FriendName Content".