gistfile1.clj

(defn server-handler []
  (proxy [ChannelHandlerAdapter] []
    (channelRead [^ChannelHandlerContext ctx ^ByteBuf msg]
      (.write ctx msg)
      (.flush ctx))
    (exceptionCaught [^ChannelHandlerContext ctx ^Throwable cause]
      (.printStackTrace cause)
      (.close ctx))))

(defn handlers
  []
  (into-array ChannelHandler [(server-handler)]))

(defn run
  [port]
  (let [bosses (NioEventLoopGroup.)
        workers (NioEventLoopGroup.)]
    (try
      (let [bootstrap (doto (ServerBootstrap.)
                        (.group bosses workers)
                        (.channel NioServerSocketChannel)
                        (.childHandler (proxy [ChannelInitializer] []
                                         (initChannel [^SocketChannel ch]
                                           (-> (.pipeline ch)
                                               (.addLast (handlers))))))
                        (.option ChannelOption/SO_BACKLOG (int 128))
                        (.childOption ChannelOption/SO_KEEPALIVE true))
            f (.sync (.bind bootstrap (int port)))
            channel (.channel f)]
        (.sync (.closeFuture channel)))
         (finally
           (.shutdownGracefully workers)
           (.shutdownGracefully bosses)))))