address use error

Could you point out why I am getting this error, as I restarted the machine and also killed required process?

Traceback (most recent call last):
  File "aem_hacker.py", line 1532, in <module>
    main()
  File "aem_hacker.py", line 1513, in main
    httpd = run_detector(args.port)
  File "aem_hacker.py", line 1475, in run_detector
    httpd = HTTPServer(('', port), handler)
  File "/usr/lib/python3.5/socketserver.py", line 441, in __init__
    self.server_activate()
  File "/usr/lib/python3.5/socketserver.py", line 463, in server_activate
    self.socket.listen(self.request_queue_size)
OSError: [Errno 98] Address already in use