Networking & Firewall (Ss/Netstat/Iptables/Nftables/Curl)

Stop curl from lying to you about failed connections

🧩 The Challenge

Everyone thinks curl is just for downloading files, but then you use it to debug a service and it gives you a generic “couldn’t connect” error. You’re left staring at the screen wondering if it’s the firewall, the DNS, or just a service that died.

💡 The Fix

Start using the verbose flag properly and dump the output to a file, or just ask it to show you the headers. It saves you from guessing if the request even left your NIC.

curl -Iv http://your-service-url:port

⚙️ Why It Works

Adding the -v flag pulls back the curtain on the TCP handshake and the HTTP headers, which immediately tells you if you’re hitting a proxy, a 404, or if the connection is getting dropped entirely by iptables. It takes the guesswork out of the network stack.

🚀 Pro-Tip: Pipe it into grep to hide the noise and see just the connection status.

Linux Tips & Tricks | © ngelinux.com | 10/18/2026