Connect() failed (111: Connection refused) while connecting to upstream


I’m getting this error on my home page :

An error occurred.

Sorry, the page you are looking for is currently unavailable.
Please try again later.

If you are the system administrator of this resource then you should
check the error log for details.

Faithfully yours, nginx.

Please anybody can help ?
I’m using TCP / IP connection instead of socket connection, I switched
from socket to TCP / ip because sockets are not scale able.