[CentOS] how to let other people know my hostname through IP address

[dxuranus <dxuranus@xxxxxxxxx>]

  i have a public hostname "a" (not my machine name)on internet and my
ip is xx.xx.xx.xx;
  the problem is other people can get my ip through hostname.but if he
try to get my hostname through ip he always failed.
  the case above is in my program (i make it) ,what can i do for this?

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