Rust whois client

whois.rs

use std::io::prelude::*;
use std::net::TcpStream;
use std::io::BufReader;
use std::env;

fn get_tld_server(tld: &str) -> Option<String> {
    let mut stream = TcpStream::connect("whois.iana.org:43").unwrap();
    stream.write_all(format!("{}\n", tld).as_bytes()).unwrap(); //Send the tld

    let reader = BufReader::new(stream);
    for line in reader.lines() {
        let line = line.unwrap();
        let parts: Vec<String> = line.splitn(2, ":").map(|x| x.to_string()).collect();
        if parts.len() == 2 {
            if parts[0].to_lowercase() == "whois" {
                return Some(parts[1].trim().to_string());
            }
        }
    }

    return None;
}

fn get_whois_data(domain: &str) -> Vec<String> {
    let mut next_server: Option<String> = None;
    let mut whois_data = Vec::new();

    let domain = domain.to_string();
    let tld = domain.split(".").last().unwrap(); // Get the top-level domain
    let tld_server = match get_tld_server(tld) {
        Some(server) => server,
        None => {
            whois_data.push(format!("Can't find a whois server for {}", domain));
            return whois_data;
        }
    };
    let mut stream = TcpStream::connect((&tld_server[..], 43)).unwrap();
    stream.write_all(format!("{}\n", domain).as_bytes()).unwrap();
    let reader = BufReader::new(stream);

    for line in reader.lines() {
        let line = line.unwrap();
        let parts: Vec<String> = line.splitn(2, ":").map(|x| x.to_string()).collect();
        if parts.len() == 2 {
            if parts[0].to_lowercase().trim() == "whois server" && !parts[1].trim().is_empty() {
                next_server = Some(parts[1].trim().to_owned());
            }
        }
        whois_data.push(line);
    }

    match next_server {
        Some(server) => {
            let mut stream = TcpStream::connect((&server[..], 43)).unwrap();
            stream.write_all(format!("{}\n", domain).as_bytes()).unwrap();
            let reader = BufReader::new(stream);

            for line in reader.lines() {
                let line = line.unwrap();
                whois_data.push(line);
            }
        },
        None => {}
    }

    return whois_data;
}

fn main() {
    let domain = match env::args().nth(1) {
        Some(domain) => domain,
        None => {
            println!("Please enter a domain");
            return;
        }
    };
    for line in get_whois_data(&domain).iter() {
        println!("{}", line);
    }
}