在80监听时，Nginx端口转发不起作用

Question

我正在尝试使用nginx将所有流量从端口80转发到端口5000。

这是我的/etc/nginx/sites-available/default文件（与/etc/nginx/sites-enabled/default链接）：

server {
    listen 80;
    server_name mysite.com www.mysite.com;
    location / {
        proxy_pass http://127.0.0.1:5000;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
        proxy_redirect off;
     }
}

当我尝试访问我的网站时，什么都不会显示。但是，我尝试将侦听端口更改为其他端口（例如8080），并且在执行此操作时，端口转发会起作用。因此，似乎有关端口80的某些事情不接受我的配置。

此外，当我检查端口80上的进程时，它表明nginx正在那里监听。因此，我也不认为有其他过程在干扰。

我还能缺少什么？为什么端口80的行为不同于我尝试的任何其他端口？

编辑：添加了nginx.conf

user www-data;
worker_processes auto;
pid /run/nginx.pid;

events {
    worker_connections 768;
    # multi_accept on;
}

http {

    ##
    # 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_disable "msie6";

    # 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;
#   }
#}

编辑2：netstat

ubuntu@ip-xxx-xx-xx-xxx:~$ sudo netstat -anpl | grep 80
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      5866/nginx -g daemo