MacOS 7.12.1 - Port XXXX is not open, could not start functions emulator

[REQUIRED] Environment info

firebase-tools: 7.12.1

Platform:macOS 10.15.2 Catalina

[REQUIRED] Test case

Run emulators:start --only functions on above environment

[REQUIRED] Steps to reproduce

Run emulators:start --only functions

[REQUIRED] Expected behavior

Expected the emulator to start on port 5001.

[REQUIRED] Actual behavior

Emulator does not start

i  emulators: Starting emulators: functions
i  Shutting down emulators.
⚠  Port 5001 is not open, could not start functions emulator.
i  To select a different port for the emulator, update your "firebase.json":
    {
      // ...
      "emulators": {
        "functions": {
          "port": "PORT"
        }
      }
    }
i  Shutting down emulators.

Error: Could not start functions emulator, port taken.

[samtstern]

@TomKaltz do things work better if you modify your firebase.json to set the emulators host to 0.0.0.0 like this:

{
  // .. other stuff ...
  "emulators": {
    "functions": {
      "host": "0.0.0.0",
      "port": 5001
     }
  }
}

[davidko604]

Also encountered the same issue. In my terminal I first ran below command to see a list of processes running that that port.

sudo lsof -i :5001

I then ran below command to kill the process by PID #.

sudo kill -9 PID#

Will try the adjusting the host as above to potentially avoid this issue in the future.