so Box<dyn std::error::Error> is automatically returned via ? used in the next line?

can we use 0.0.0.0 like in all other services?

50051 is a tunnelbroker's port, we probably want to use 50054 - https://github.com/CommE2E/comm/blob/2463ccbd032927571d7c7a968df199a1563a35d3/services/.env

what this parse does here?

So this is just calling an argument-less function? Or why there are no ()?

The following line is doing a lot. compile_protos returns a Result enum, which has two variants, Ok(r) and Err(e). If compilation is successful, the function returns Ok(r) and the ? unwraps the enum. If it fails, the function returns Err(e), and the ? calls into (a trait method) to convert the error to Box<dyn std::error::Error>. The reason we Box the error here is to preserve the original error.

Yeah, I'll change it to 0.0.0.0:50054.

parse() converts the &str to a SocketAddr. The rust compiler is pretty smart... it sees that addr is being used as an argument for serve() below, and that function takes a SocketAddr, so it knows to convert addr to that type when parse() is called.

I don't understand this question, can you rephrase?

Yeah, await is a special keyword. It's not actually a method, it's just how async Rust works. See https://rust-lang.github.io/async-book/01_getting_started/04_async_await_primer.html.

I think I get it, thanks.

It, in fact, looks smart but honestly, a little confusing. Could you maybe explain it more or point out where I can look for answers (docs are ok, but the best I can get is a tutorial with a brief explanation that gets straight to the point)?

My basic question is: what is the rule here? So the compiler sees that addr has an implicit type, then it sees the parse method. At this point, I'm confused about the parse method. What is it? Is it some kind of magic method that is supposed to be implemented in certain types, or is it a global method for parsing between types?

Thx Jim. Varun, I was confused about why there is .await instead of .await().

https://doc.rust-lang.org/std/primitive.str.html#method.parse

parse() is a method that the str type implements. the compiler checks if SocketAddr (the implicit type of addr) implements the FromStr trait, which it does: https://doc.rust-lang.org/std/net/enum.SocketAddr.html#impl-FromStr. so, when parse() is called, SocketAddr's from_str() method is implicitly used.