command line argument parsing for recv

hptp-recv/src/main.rs

@@ -1,5 +1,28 @@
 extern crate hptp;
 
-fn main() {
-    println!("{}", hptp::RECV_GREETING);
+#[derive(Debug)]
+struct Hostname(String, u16);
+
+fn go(hn: Hostname) {
+    println!("{:?}", hn)
+}
+
+fn usage() {
+    print!("usage:\n./3700recv <host-ip>:<host-port>\n")
+}
+
+fn parse_args() -> Result<Hostname, ()> {
+    let mut args = std::env::args();
+    let arg = args.nth(1).ok_or(())?;
+    let i = arg.find(':').ok_or(())?;
+    let ip: String = arg[..i].into();
+    let port: u16 = arg[i + 1..].parse::<u16>().map_err(|_| ())?;
+    Ok(Hostname(ip, port))
+}
+
+fn main() {
+    match parse_args() {
+        Ok(x) => go(x),
+        Err(_) => usage(),
+    }
 }