Port 80 not open. Still gets 404 when curl

Question

Weird issue I'm facing currently! There is nothing running on port 80.

Still curl gives 404 page not found. I can telnet to port 80 and even start a container exposing port 80 (host). But no requests reaches the container!

Any idea what might be going on? How do I debug this?

$ netstat -tulpn | grep :80
tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN      -                   
tcp6       0      0 :::8000                 :::*                    LISTEN      -                   
$ curl localhost
404 page not found

Answer 1

In addition to Matthew's comment suspecting internal nat redirect

• iptables -vnL -t nat or nft list ruleset ip

perhaps you could directly inspect port 80. These are some of the ways to do that:

• ss -4tlnp -o state LISTENING '( sport = :80 )'
• lsof -i:80
• do a verbose tcpdump
• do a verbose portscan with nmap
• or, be even more explicit when testing with curl, ie curl -v http://localhost:80