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