Reverse proxy and 502

Articles

• ss — sockets and ports — Shows who is listening on ports and which connections are open; a netstat replacement, faster with many connections.
• HTTP — requests, responses, status codes and headers — An application request-response protocol used by web services.
• curl — HTTP requests from the console — curl sends HTTP and HTTPS requests from the console: status code, headers, the whole exchange, certificate checks.
• Unix sockets — processes talking through a file — A unix socket is a file through which processes on one machine exchange data; connecting needs write permission on it.
• systemd — System and service manager that manages units and their dependencies.
• nginx — web server and reverse proxy — A web server and reverse proxy whose configuration should be checked before applying changes.