CODEWITHSUNDEEP
rust
tteo57
tteo57

Reputation: 11

Why doesn't the for loop exit when using Tcplistener incoming iterator

Looking at the rust bible, there is the following code:

use std::net::TcpListener;

fn main() {
    let listener = TcpListener::bind("127.0.0.1:7878").unwrap();

    for stream in listener.incoming() {
        let stream = stream.unwrap();

        println!("Connection established!");
    }
}

I was wondering why the for loop doesn't exit. After one iteration of the for loop (ie. if nobody connects), shouldn't the for loop finish and the main function exit?

Upvotes: 2

Views: 486

Answers (1)

kmdreko
kmdreko

Reputation: 60177

This is intended. From the documentation for TcpListener regarding incoming() notes:

The returned iterator will never return None and will also not yield the peer's SocketAddr structure. Iterating over it is equivalent to calling accept in a loop.

And accept() notes:

This function will block the calling thread until a new TCP connection is established.

So it is designed to infinitely wait for connections and doesn't yield execution until one does.

You can change this behavior by calling listener.set_nonblocking(true) to have accept (and therefore the incoming iterator) to immediately yield with the error io::ErrorKind::WouldBlock if no connections are pending.

Upvotes: 5

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