HTTP

nginx — web server and reverse proxy

nginx serves sites from disk and forwards requests to applications; it picks a site by Host, nginx -t checks the config.

HTTP — requests, responses, status codes and headers

HTTP is the web protocol: a client sends a method, path and headers; the server replies with a code, headers, body.

curl — HTTP requests from the console

curl sends HTTP and HTTPS requests from the console: status code, headers, the whole exchange, certificate checks.

wget — downloading files over the network

Downloads files with resume and recursion; -r without -np and -l has no brakes and can mirror a whole site.

jq — processing JSON on the command line

Parsing and filtering JSON on the command line — fields, arrays, filters, formatting.

TLS and certificates — openssl, the chain, verification

A TLS certificate binds a server key to a site name; openssl reads its fields, checks the chain and issues a new one.