The virtual server section

Any context beginning with the keyword server is considered a virtual server section. It describes a logical separation of a set of resources that will be delivered under a different server_name directive. These virtual servers respond to the HTTP requests, and are contained within the http section.

A virtual server is defined by a combination of the listen and server_name directives. The listen directive defines an IP address/port combination or path to a UNIX-domain socket:

listen address[:port];
listen port;
listen unix:path;

The listen directive uniquely identifies a socket binding under NGINX. There are a number of optional parameters that listen can take:

The listen parameters	Explanation	Comments
default_server	This parameter defines this address/port combination as being the default value for the requests bound here.
setfib	This parameter sets the corresponding FIB for the listening socket.	This parameter is only supported on FreeBSD and...