If already running statsd on the default port, agent fails with no error

[MisterRayCo]

https://datadog.desk.com/agent/case/3875

[clutchski]

It'd be good to raise a better message here, e.g. "A program is already listening on port XYZ"

[elijahandrews]

Haven't been able to reproduce this one. While already running statsd:

➜  dd-agent git:(master) ✗ python dogstatsd.py
Log file is unwritable: '/var/log/datadog/dogstatsd.log'
2013-05-14 13:00:18,488 | INFO | dd.dogstatsd | dogstatsd(dogstatsd.py:218) | Adding sig handler
2013-05-14 13:00:18,488 | INFO | dd.dogstatsd | dogstatsd(dogstatsd.py:78) | Reporting to localhost:9000 every 10s
2013-05-14 13:00:18,489 | INFO | dd.dogstatsd | dogstatsd(dogstatsd.py:73) | Stopping reporter
2013-05-14 13:00:18,490 | INFO | dd.dogstatsd | dogstatsd(dogstatsd.py:229) | Stopped
Traceback (most recent call last):
  File "dogstatsd.py", line 322, in <module>
    sys.exit(main())
  File "dogstatsd.py", line 301, in main
    daemon.run()
  File "dogstatsd.py", line 223, in run
    self.server.start()
  File "dogstatsd.py", line 174, in start
    self.socket.bind(self.address)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/socket.py", line 224, in meth
    return getattr(self._sock,name)(*args)
socket.error: [Errno 48] Address already in use

[remh]

You should probably use the same environment:
centos 6, then install the agent via the repo and look at the logs.