I'm having a problem on a new ethereum install on a Mac:

Fatal: Error starting protocol stack: listen udp :30303: bind: address already in use

Any suggestions to fix would be greatly appreciated.


You might have already installed and launched an geth instance before. It might as well be other services listen on the same port, though very unlikely.

You can use the following command to kill the existing process:

$ # Get <PID> of the process occupying the port
$ lsof -i tcp:30303
$ kill -QUIT <PID> 

Then reload the wallet.

  • It would be better to try kill -INT <pid> first as Geth has an explicit handler for SIGINTs but not for SIGQUITs. That way if there is an instance already running, it's more likely to exit gracefully. (Also, a QUIT signal leads to an explicit core dump.) ethereum.stackexchange.com/questions/10566/… Mar 22 '17 at 9:28
  • Tried kill -INT <pid> first, still had issue, then used kill -QUIT <PID>, issue solved!
    – BioponX
    Mar 22 '17 at 13:31
  • Glad to know it's resolved! Mar 23 '17 at 2:22

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