设置防火墙后，nginx 出现 502 bad gateway

Question

我的服务器正在运行，然后我为一堆端口添加了防火墙！现在我收到错误：

502 Bad Gateway

nginx/1.4.6 (Ubuntu)

Nginx

server {
  listen 80;
  server_name 45.79.80.140;


  #These lines create a bypass for certain pathnames
  #www.example.com/test.js is now routed to port 3000 
  #instead of port 80
  location / {
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
        proxy_http_version 1.1;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $host;
        proxy_pass http://socket_nodes;
  #    proxy_pass http://localhost:5000;
  #    proxy_set_header Host $host;
  }
}
  upstream socket_nodes {
    ip_hash;
    server srv1.app.com:5000 weight=5;
    server srv2.app.com:5000;
    server srv3.app.com:5000;
    server srv4.app.com:5000;
}

IP 表

*filter

#  Allow all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
-A INPUT -i lo -j ACCEPT
-A INPUT -d 127.0.0.0/8 -j REJECT

#  Accept all established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

#  Allow all outbound traffic - you can modify this to only allow certain traffic
-A OUTPUT -j ACCEPT

#  Allow HTTP and HTTPS connections from anywhere (the normal ports for websites and SSL).
-A INPUT -p tcp --dport 80 -j ACCEPT
-A INPUT -p tcp -m tcp --dport 3000 -j ACCEPT
-A INPUT -p tcp --dport 443 -j ACCEPT

#  Allow SSH connections-A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT

#  Allow ping
-A INPUT -p icmp --icmp-type echo-request -j ACCEPT

#  Log iptables denied calls
-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7

#  Drop all other inbound - default deny unless explicitly allowed policy
-A INPUT -j DROP
-A FORWARD -j DROP

COMMIT