whiel running mongodb couldnot connect to server 127.0.0.0:27017 code example

Example 1: Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed: SocketException: Error connecting to 127.0.0.1:27017 :: caused by :: Connection refused :

sudo service mongodb start

Example 2: Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed

systemctl enable  mongod
systemctl start  mongod

#reboot your machine

mongo