Failed to start devlopment server — BindError: Unable to find a consistent port localhost

Question

Google-app-engine development server runs great yesterday, but when I try to start it today. It only shout out this Error.

I tried use lsof -i:8080 / <

Answer 1

In my case just restarting the terminal worked.

Answer 2

dev_appserver.py . --port 4000

this fixed it for me.

Answer 3

I solved this issue by passing an explicit api port to dev_appserver.py:

dev_appserver.py path/to/project --api_port 3000

I was unable to solve the issue by editing the hosts file or passing --port / --host to dev_appserver.py.

I didn't identify the root cause.

Answer 4

Similar to what was posted, I had this issue and fixed it by altering the hosts file. The issue was with IPv6 addresses redirecting to localhost:

In my hosts file I had

127.0.0.1    localhost
::1          localhost 
fe80::1%lo0  localhost

And I commented out the IPv6 addresses to give

127.0.0.1     localhost
#::1          localhost 
#fe80::1%lo0  localhost

I'm not sure this is a viable permanent solution as I imagine it's important to have the IPv6 numerical addresses for localhost to be in the hosts file but it works for now until a proper fix is released.

Answer 5

While I never seen that before try running it on a different port or even using a different host:

dev_appserver.py /path/to/project --port 8888 --host 127.0.0.1

Where for host add your current IP address.

Answer 6

This can be caused by multiple entries in your hosts file for 'localhost'.

For example in file /etc/hosts:

127.0.0.1 localhost
127.0.0.1 mymachinename localhost

if you delete all mappings but one for localhost, the problem will hopefully be resolved.

127.0.0.1 mymachinename localhost

This is a known issue and as far as I understand it will be corrected in a future release.