udp punch hole in rust

main.rs
use std::net::{SocketAddr, UdpSocket};

const SERVER_ADDR: &str = "0.0.0.0:4000";
const CLIENT_ADDR: &str = "0.0.0.0:0";

fn main() -> std::io::Result<()> {
    // Create server socket
    let server_socket = UdpSocket::bind(SERVER_ADDR)?;
    server_socket.set_nonblocking(true)?;

    // Create client socket
    let client_socket = UdpSocket::bind(CLIENT_ADDR)?;
    client_socket.set_nonblocking(true)?;

    // Send a message from server to client
    let server_addr = "127.0.0.1:3000";
    let buf = "Hello from server".as_bytes();
    let sent_bytes = server_socket.send_to(buf, server_addr)?;

    // Send a message from client to server
    let client_addr = "127.0.0.1:2000";
    let buf = "Hello from client".as_bytes();
    let sent_bytes = client_socket.send_to(buf, client_addr)?;

    // Attempt to connect both sockets by sending messages to each other
    let mut server_success = false;
    let mut client_success = false;
    let mut buf = [0u8; 1024];

    for i in 0..10 {
        // Send a message from server to client
        let server_addr = "127.0.0.1:2000";
        let buf = format!("ping from server ({})", i).as_bytes();
        let sent_bytes = server_socket.send_to(buf, server_addr)?;

        // Receive a message from client
        if let Ok((bytes_read, client_addr)) = client_socket.recv_from(&mut buf) {
            let msg = std::str::from_utf8(&buf[0..bytes_read])?;
            println!("Received message from client: {}", msg);
            client_success = true;
        }

        // Send a message from client to server
        let client_addr = "127.0.0.1:3000";
        let buf = format!("ping from client ({})", i).as_bytes();
        let sent_bytes = client_socket.send_to(buf, client_addr)?;

        // Receive a message from server
        if let Ok((bytes_read, _server_addr)) = server_socket.recv_from(&mut buf) {
            let msg = std::str::from_utf8(&buf[0..bytes_read])?;
            println!("Received message from server: {}", msg);
            server_success = true;
        }

        if server_success && client_success {
            println!("UDP Hole Punching successful!");
            break;
        }
    }

    Ok(())
}
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