gistfile1.clj

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

(defn server-response
  [packet]
  (Unpooled/copiedBuffer "Hello, world!" CharsetUtil/UTF_8))

(defn packet-content
  [^DatagramPacket packet]
  (str (.content packet)))

(defn server-handler []
  (proxy [SimpleChannelInboundHandler] []
    (messageReceived [^ChannelHandlerContext ctx ^DatagramPacket packet]
      (let [content (packet-content packet)
            res (DatagramPacket. (server-response packet) (.sender packet))]
        (println content)
        (.write ctx res)))
    (channelReadComplete [^ChannelHandlerContext ctx]
      (.flush ctx))
    (exceptionCaught [^ChannelHandlerContext ctx ^Throwable cause]
      (.printStackTrace cause))))

(defn run
  [port]
  (let [group (NioEventLoopGroup.)]
    (try
      (let [bootstrap (doto (Bootstrap.)
                        (.group group)
                        (.channel NioDatagramChannel)
                        (.option ChannelOption/SO_BROADCAST true)
                        (.handler (server-handler)))]
        (-> (.bind bootstrap (int port))
            (.sync)
            (.channel)
            (.closeFuture)
            (.await)))
      (finally
        (.shutdownGracefully group)))))