category 04 / 10

Networking

Ports, DNS, HTTP requests, and waiting for services.

004

entries

4 min

avg read

all 004 debugging 004 bash 001 dev-tcp 001 ports 001 openssl 001 tls 001 certificates 001 curl 001 http 001 latency 001 dig 001 dns 001

039Check if a remote port is open when netcat is not installedtimeout 3 bash -c '</dev/tcp/bash-hacks.com/443' && echo open || echo closed2026-10-084 min 026See when a TLS certificate expires without opening a browseropenssl s_client -connect bash-hacks.com:443 -servername bash-hacks.com </dev/null 2>/dev/null | openssl x509 -noout -subject -issuer -dates2026-09-214 min 017Find out which part of an HTTP request is actually slowcurl -sS -o /dev/null -w "dns %{time_namelookup}\ntcp %{time_connect}\ntls %{time_appconnect}\nttfb %{time_starttransfer}\ntotal %{time_total}\n" https://www.debian.org2026-09-074 min 008Check where a domain name actually pointsdig +short example.com2026-08-253 min

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