Archive
Short write-ups, mostly for future me.
Start with the simplest question: did the SYN get an answer? Then check whether the application ever spoke. Packet captures are most useful when you write down what you expect to see before you look.
A few habits help: label both directions, keep timestamps, and avoid changing more than one variable per experiment.
A fallback route that silently bypasses the intended path is a classic source of surprises. If the preferred path is unavailable, dropping the traffic is often safer than quietly taking another one.
The same idea applies to configuration: make the safe state explicit, and make the unsafe state require a deliberate choice.
One binary, one config file, one job. Resist the urge to add a database until the file is actually a problem. Small services are easier to observe, easier to replace, and much easier to explain.