root@mayton-HP-250-G4-Notebook-PC:~# uname -a
Linux mayton-HP-250-G4-Notebook-PC 4.15.0-45-generic #48-Ubuntu SMP Tue Jan 29 16:28:13 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
root@mayton-HP-250-G4-Notebook-PC:~# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

server {
    listen 127.0.0.1:5005;
}

root@mayton-HP-250-G4-Notebook-PC:~# nginx -t
nginx: [emerg] "server" directive is not allowed here in /etc/nginx/nginx.conf:6
nginx: configuration file /etc/nginx/nginx.conf test failed

root@mayton-HP-250-G4-Notebook-PC:/etc/nginx# cat nginx.conf 
user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;


events {
	worker_connections 768;
	# multi_accept on;
}

http {

        server {
          listen 127.0.0.1:5005;
        }


	##
	# Basic Settings
	##

	sendfile on;
	tcp_nopush on;
	tcp_nodelay on;
	keepalive_timeout 65;
	types_hash_max_size 2048;
	# server_tokens off;

	# server_names_hash_bucket_size 64;
	# server_name_in_redirect off;

	include /etc/nginx/mime.types;
	default_type application/octet-stream;

	##
	# SSL Settings
	##

	ssl_protocols TLSv1 TLSv1.1 TLSv1.2; # Dropping SSLv3, ref: POODLE
	ssl_prefer_server_ciphers on;

	##
	# Logging Settings
	##

	access_log /var/log/nginx/access.log;
	error_log /var/log/nginx/error.log;

	##
	# Gzip Settings
	##

	gzip on;

	# gzip_vary on;
	# gzip_proxied any;
	# gzip_comp_level 6;
	# gzip_buffers 16 8k;
	# gzip_http_version 1.1;
	# gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

	##
	# Virtual Host Configs
	##

	include /etc/nginx/conf.d/*.conf;
	include /etc/nginx/sites-enabled/*;
}


#mail {
#	# See sample authentication script at:
#	# http://wiki.nginx.org/ImapAuthenticateWithApachePhpScript
# 
#	# auth_http localhost/auth.php;
#	# pop3_capabilities "TOP" "USER";
#	# imap_capabilities "IMAP4rev1" "UIDPLUS";
# 
#	server {
#		listen     localhost:110;
#		protocol   pop3;
#		proxy      on;
#	}
# 
#	server {
#		listen     localhost:143;
#		protocol   imap;
#		proxy      on;
#	}
#}