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I'm currently setting up a Linux VPS (Debian-based), to run a Flask app and a python script to make API calls (the API only works over IPv4, not IPv6).

I'm having trouble with outgoing HTTPS connections (port 443). Here's what's happening:

  • Ping and traceroute to external IPs (e.g. 1.1.1.1, 142.251.40.100) work fine.

  • But any HTTPS request (e.g. curl https://www.google.com or openssl s_client -connect) hangs and never completes.

  • There are no firewall rules active (iptables -F, policies all set to ACCEPT).

  • There's no proxy configured (echo $http_proxy and $https_proxy return nothing).

  • tcpdump on the main interface shows no outgoing or incoming traffic for port 443.

  • nmap -Pn -p 443 shows port 443 as filtered for external servers (like Google).

  • Outgoing connections on other ports (e.g., ping, DNS, etc.) seem to work.

I also verified the default route (ip route show) and it looks fine. The interface has a public IP, and curl or wget to HTTP or HTTPS just hangs.

Reaching the Hostinger assistance, they stated: "your 443 and 80 port are opened so the network connection should be working".

I have no more ideas, any tips?

Thank you for your reading and help!

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  • You say you can ping by IP address. Can you ping by name, e.g. ping bbc.co.uk Commented Apr 29 at 9:58
  • Are any rules loaded in iptables -t nat or iptables -t mangle? Or more generally iptables-save plus nft list ruleset (if installed)? Commented Apr 29 at 10:17
  • @ChrisDavies yes, ping by name is working Commented Apr 29 at 14:23
  • @grawity there is no rule for INPUT, OUTPUT, POSTROUTING, all set with an ACCEPT policy Commented Apr 29 at 14:23
  • 1
    Does tcpdump show any traffic towards the target IPv4 or IPv6 address? Commented Apr 29 at 22:27

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