port-scanner.clj

(ns port-scanner
  (:import [java.net Socket InetSocketAddress]))

(defn port-open? [hostname port timeout]
  (try
   (with-open [sock (Socket.)]
     (.connect sock (InetSocketAddress. hostname port) timeout)
     port)
   (catch Exception e false)))

(let [hostname (or (first *command-line-args*)
                   (do (println "Usage: scanner <hostname>")
                       (System/exit 1)))]
  (println (str "Scanning " hostname "..."))
  (doseq [port (doall (map #(future (port-open? hostname % 5000)) (range 1 1024)))]
    (when @port (println @port "is open"))))