Health check msg

[ganbolor]

Sometimes following error occurred when the client is disconnected and then reconnected.
Error: "The nick '" + userInfo.Nick + "' is being used by another user. Please select another one.
Sometimes, server don't know whether client is disconnected or connected.

To solve this issue:

1. Server will send check msg to clients every 10 sec.
2. Server will check client name because may be, client name is same previous connected clients.
   a. if client name is same, Server will respond the above error.
   Error: "The nick '" + userInfo.Nick + "' is being used by another user. Please select another one.
   b. if client name is not same, Server will receive new user.