A small test with UDP

udptest.clj

(ns udptest.core
  (:import [java.net DatagramSocket
                     DatagramPacket
                     InetAddress]
           [java.io  BufferedReader
                     InputStreamReader]))

(set! *warn-on-reflection* true)

(defn- client []
  (println "[CLIENT] Starting")
  (let [inFromUser   (BufferedReader. (InputStreamReader. System/in))
        clientSocket (DatagramSocket.)
        IPAddress    (InetAddress/getByName "localhost")
        sendData     (byte-array 1024)
        receiveData  (byte-array 1024)
        sentence     (.readLine inFromUser)
        sendData     (.getBytes sentence)
        sendPacket   (DatagramPacket. sendData (alength sendData) IPAddress 9876)
        _            (.send clientSocket sendPacket)
        receivePacket (DatagramPacket. receiveData (alength receiveData))
        _            (.receive clientSocket receivePacket)
        modifiedSentence (String. (.getData receivePacket))
        _            (println "FROM SERVER:" modifiedSentence)]
      (.close clientSocket)))


(defn- server []
  (println "[SERVER] Starting")
  (let [serverSocket (DatagramSocket. 9876)
        receiveData  (byte-array 1024)
        sendData     (byte-array 1024)]
    (loop [receiveData receiveData
           sendData    sendData]
      (let [receivePacket (DatagramPacket. receiveData (alength receiveData))
            _             (.receive serverSocket receivePacket)
            sentence      (String. (.getData receivePacket))
            _             (println "[SERVER] RECEIVED:" sentence)
            IPAddress     (.getAddress receivePacket)
            port          (.getPort receivePacket)
            capitalizedSentence (.toUpperCase sentence)
            sendData      (bytes (.getBytes capitalizedSentence))
            sendPacket    (DatagramPacket. sendData (alength sendData) IPAddress port)]
        (.send serverSocket sendPacket)
        (recur (bytes receiveData) (bytes sendData))))))

(defn -main[& args]
  (.start (Thread. ^Runnable server))
  (.start (Thread. ^Runnable client)))