使用netty-4.x的clojure udp服务，根据netty-4.x的java demo程序翻译过来的。

netty-4-udp-demo.clj

(ns mytest.udp
  (:import (java.net InetSocketAddress
                     InetAddress)
           (io.netty.bootstrap Bootstrap)
           (io.netty.channel ChannelOption
                             EventLoopGroup
                             ChannelHandlerContext
                             ChannelInitializer
                             ChannelHandler
                             SimpleChannelInboundHandler)
           (io.netty.channel.nio NioEventLoopGroup)
           (io.netty.channel.socket DatagramPacket)
           (io.netty.channel.socket.nio NioDatagramChannel)
           (io.netty.util CharsetUtil))
  (:use [clojure.tools.logging]))

(defn udp-echo
  [content]
  (let [text (.toString content CharsetUtil/UTF_8)]
    (prn (format "Recieved message: %s" text))
    text))

(defn make-udp-handler
  [handle]
  (proxy [SimpleChannelInboundHandler] []
    (channelRead0 [context packet]
      (let [content (.content packet)]
        (handle content)))
    
    (channelReadComplete [context]
      (.flush context))
    
    (exceptionCaught [context exception-event]
      (warn (.getCause exception-event) "UDP handler caught"))))

(defn udp-server
 ([] (udp-server {}))
 ([opts]
    (let [opts (merge {:addr (InetAddress/getByName "0.0.0.0")
                       :port 5140
                       :handle udp-echo}
                      opts)
          group (NioEventLoopGroup.)
          bootstrap (Bootstrap.)
          handler (make-udp-handler (:handle opts))
          addr (:addr opts)
          port (:port opts)]
      (doto bootstrap
        (.group group)
        (.channel NioDatagramChannel)
        (.option ChannelOption/SO_BROADCAST true)
        (.handler handler))

      (let [f (-> bootstrap
                  (.bind addr port)
                  (.sync))]
        (-> f
            (.channel)
            (.closeFuture)
            (.sync))))))