Servidor TCP básico. Permite várias conexões simultâneas, mas os usuários não se conversam.

server-core.clj

(ns server.core)

(import [java.net ServerSocket])
(import [java.io DataInputStream 
                 DataOutputStream])

(defn- debug [message]
  (println (str "[" (.getName (Thread/currentThread)) "] " message)))

(defn- start-server 
  ([fun]
    (println "Using default settings")
    (start-server fun 9876))
  ([fun port]
    (println (str "Listening port " port))
    (do
      (println "Starting connection")
      (let [server (ServerSocket. port)]
        (loop [socket (.accept server)]
          (.start 
            (Thread. #(fun socket)))
          (recur (.accept server)))))))

(defn- callback [socket]
  (let [in  (DataInputStream. (.getInputStream socket))
        out (DataOutputStream. (.getOutputStream socket))]
    (debug "connected")
    (.writeBytes out "\nHello stranger. Type exit to leave and press ENTER\n\n$ ")

    (loop [user-input (.readLine in)]
      (when-not (= "exit" user-input)
                (do (debug user-input))
                    (.writeBytes out (str "Read: " user-input "\n\n$ "))
                    (recur (.readLine in))))

    (.writeBytes out "\nGoodbye stranger.\n\n")
    (.close socket)
    (debug "left")))

(defn -main []
  (start-server callback))