time client NIST

time_client.rs

use std::net::TcpStream;
use std::io::{self, Read};
use std::time::{SystemTime, UNIX_EPOCH};

fn get_current_unix_timestamp() -> u64 {
    let start = SystemTime::now();
    
    let since_the_epoch = start.duration_since(UNIX_EPOCH).expect("Ehmmm..");

    // Adjust for the difference between 1900 and 1970
    let seconds_since_1900 = 2208988800; 

    seconds_since_1900 + since_the_epoch.as_secs()
}

fn get_nist_time(host: &str, port: u16) -> Result<u32, io::Error> {
    let address = format!("{}:{}", host, port);

    let mut stream = TcpStream::connect(&address)?;

    let mut buffer = [0; 4];
    stream.read(&mut buffer)?;

    let number = u32::from_be_bytes(buffer);
    Ok(number)
}

fn main() {
    let host = "time.nist.gov";
    let port = 37;

    match get_nist_time(host, port) {
        Ok(nist_time) => {
            println!("NIST time: {}", nist_time);

            let local = get_current_unix_timestamp();
            println!("Syst time: {}", local);

            println!("Diff: {}", local - nist_time as u64);
        }
        Err(e) => {
            println!("Failed to read NIST time: {}", e);
        }
    }
}