PHP 7 php7.0-fpm.sock http error 500

I am using Nginx + PHP7 and trying use the wordpress social login

Its successfully working in

fastcgi_pass 127.0.0.1:7777;

But Fails when using

fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;

Os is Ubuntu 14.04.

I tried referring the error 500 reference in the Plugin support page and the reason is Sessions issue .

I wish to use Php socket ,kindly help me to understand what changes i have to do in the Php or nginx files to support the sessions