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

Stop wondering why curl hangs on internal services

🧩 The Challenge

You’ve got a web service that times out for no reason, but the logs show nothing. I’ve wasted entire afternoons chasing silent drops when the firewall was just quietly blackholing my connection.

💡 The Fix

Use the –trace-ascii flag to watch exactly how the TCP handshake unfolds. It lets you see if you’re getting stuck at the SYN/ACK stage or if the server is actually sending a reset.

curl -v --trace-ascii - http://internal.service.local:8080/health

⚙️ Why It Works

By dumping the raw traffic to your terminal, you bypass the mystery of standard error messages. It forces curl to show you the state of the socket so you don’t have to guess where the pipe is broken.

🚀 Pro-Tip: Pipe it into grep to filter for specific headers if you’re dealing with a massive response payload.

Linux Tips & Tricks | © ngelinux.com | 7/13/2026