1) The BEAM book - https://blog.stenmans.org/theBeamBook/
2) Erlang and OTP in Action by Merritt, Logan and Carlson
20 years ago, picking up OCaml, as an initial project I decided to write a password cracker to run against my WiFi router. The webserver on my WRT-54G was sending back errors, but Yahoo's webserver (more popular than Google at the time) was perfectly happy replying correctly to my HTTP client's requests.
I had to break out Ethereal (since renamed Wireshark) to debug why Yahoo was fine with my HTTP client but my WRT-54G wasn't. It turns out I didn't realize that OCaml character escapes that began with zero were still decimal, not octal (unlike C). So, I was sending a line terminator of vertical-tab shift-in instead of carriage-return line-feed. I guess kudos to whomever wrote Yahoo's webserver to make proper sense of such wonky requests, though I think it was far too liberal in what it accepted.
Depending on exactly when, you may have been hitting Yahoo's custom http server originally written by David Filo or yapache, a patched version of Apache 1.3.
Is there a good book that is focused on advanced OTP? On the internals of the BEAM and the hairier parts of the Erlang ecosystem? I can only find basic to intermediate introductory material. Perhaps I should just spend time reading the erlang website back-to-front...
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1: I'm taking a small break from writing a parallel, distributed website crawler with homegrown HTTP client. Quite fun, very fast, to replace my first, rough prototype written in Rust. The hard part is accepting that most HTTP servers on the open Internet are hopelessly broken in a million ways.