clojure server using java nio

srvclj.clj

(ns srvclj.core
  (:import [java.nio.channels ServerSocketChannel Selector SelectionKey]
           [java.nio ByteBuffer]
           [java.net InetSocketAddress])
  (:gen-class))

(def buf (ByteBuffer/allocate 1024));

(def selector (Selector/open))
(def serverChannel (ServerSocketChannel/open))
(.configureBlocking serverChannel false)

(def port 8888)
(def portAddr (InetSocketAddress. port))
(.bind (.socket serverChannel) portAddr)

(.register serverChannel selector SelectionKey/OP_ACCEPT)

(println "server started")

(defn withAccept [key]
  (println "a client come in")
  (let [socketChannel (-> key .channel .accept)]
    (.configureBlocking socketChannel false)
    (.register socketChannel selector SelectionKey/OP_READ)))

(defn withRead [key]
  (println "read data")
  (let [socket-channel (.channel key)]
    (.clear buf)
    (.read socket-channel buf)
    (.flip buf)
    (println (.getInt buf))))

(defn withUnknown [key]
  (println "unkonwn type" (.readyOps key)))

(while true
  (if (not= 0 (.select selector 3000))
    (let [keys (.selectedKeys selector)]      
      (doseq [key keys]
        (let [ops (.readyOps key)]
          (cond
            (= ops SelectionKey/OP_ACCEPT) (withAccept key)
            (= ops SelectionKey/OP_READ) (withRead key)
            :else (withUnknown key))))
      (.clear keys))))

(println "end")