title: nginx ws invalid URL prefix
body: <p>First time with <code>nginx</code>.<br>
  I have a nodejs WebSocket server listening at <code>ws://service_name:3600</code>.<br>
  I'm using <code>docker-compose</code>:</p>
  
  <pre><code>version: "2"
  services:
     # stuff
  
     service_name:
        image: imagename
        ports:
          - 3600:3600
        links:
          # stuff
          - proxy
  
     proxy:
       image: image-from-nginx-with-custom-config
       ports:
         - 80:80
         - 443:443
         - 8443:8443
  </code></pre>
  
  <p>My config:</p>
  
  <pre><code>// stuff 
  
  server {
      listen          8443;
      server_name     localhost;
      ssl on;
  
      ssl_certificate      /etc/nginx/certs/crt.pem;
      ssl_certificate_key  /etc/nginx/certs/key.pem;
  
      keepalive_timeout    60;
  
      proxy_next_upstream error timeout invalid_header http_500 http_502 http_503;
      proxy_set_header Host $host;
      proxy_set_header X-Real-IP $remote_addr;
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_set_header X-Forwarded-Proto https;
  
      location / {
          proxy_pass ws://service_name:3600;
          proxy_http_version 1.1;
          proxy_set_header Upgrade $http_upgrade;
          proxy_set_header Connection "upgrade";
      }
  }
  </code></pre>
  
  <p>I get <code>nginx: [emerg] invalid URL prefix in /etc/nginx/conf.d/default.conf</code> at startup.<br>
  So nginx doesn't recognize <code>ws</code>, what do I do?</p>