temporary change:
1. remove useless header files
2. bring new mechanism, client fetch ip from server and chat with each other
3. listencli and conncli can run
4. rename testcli and testsrv to tchatcli and tchatsrv
5. tchatcli use system() function to open new window
6. utility.h provide some wrapper func to use
7. this version is incomplete, cannot run