Nginx subdomain not routing to Node.js

Question

I have a subdomain that I want to proxy through Nginx to Node.js.

domain.tld is currently routed the standard way through /opt/nginx/conf/nginx.conf.

However, I also want subdomain.domain.tld to route to domain.tld:8000.

To do this, I put the following in /etc/nginx/sites-available/subdomain.domain.tld.conf:

http{
    server {
            listen 0.0.0.0:80;
            server_name subdomain.tld.com;
            access_log /var/log/nginx/subdomain.domain.log;

            location / {
                    proxy_pass http://127.0.0.1:8000;
            }
    }
}

Nginx seems to start up fine. The subdomain's nameservers are configured correctly.

What am I doing wrong? Thanks a ton for any help in advance.

Edit: Also, I symlinked the file from sites-available/ to sites-enabled/.

Edit: The exact contents of /opt/nginx/conf/nginx.conf:

http://pastebin.com/wZJFPx7H

Edit: The error message starting nginx:

 Starting nginx: nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use) 
 nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use) 
 nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use) 
 nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use) 
 nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use) 
 nginx: [emerg] still could not bind()

Answer 1

First off, check for any errors in the log during startup.

It may not be loading this server because of this:

proxy_pass 127.0.0.1:8000;

Which should be changed to:

proxy_pass http://127.0.0.1:8000;

Beyond that, compare the listen directive to that in your other server blocks - make sure it matches. If they're bound to a specific address instead of 0.0.0.0, then this server wouldn't be getting the requests.

edit:

For those who find this question in the future, the subdomain's server block was not being included - and the include block must be within the existing http block to avoid address binding conflicts.