[SOLVED] Handling websocket client messages with aleph

Handling websocket client messages with aleph

During my quest to learn Clojure I am currently facing problems with setting up websocket communitation. After many different approaches, I ended up using aleph.

What I managed to achieve:

handling of a new client connecting
handling a client disconnection
talking from the server to clients at will

What I lack is means to trigger a handler function whenever one of the connected clients sends something via the websocket.

My code so far:

(ns wonders7.core.handler
  (:require [compojure.core :refer :all]
            [compojure.route :as route]
            [ring.middleware.defaults :refer [wrap-defaults site-defaults]]
            [aleph.http :as http]
            [manifold.stream :as stream]
            [clojure.tools.logging :refer [info]]))

(defn uuid [] (str (java.util.UUID/randomUUID)))

(def clients (atom {}))

(defn ws-create-handler [req]
  (let [ws @(http/websocket-connection req)]
    (info "ws-create-handler")
    (stream/on-closed ws #(swap! clients dissoc ws))
    (swap! clients assoc ws (uuid))))

(defroutes app-routes
  (GET "/ws" [] ws-create-handler)
  (route/not-found "Not Found"))

(def app
  (wrap-defaults app-routes site-defaults))

(defn msg-to-client [[client-stream uuid]]
  (stream/put! client-stream "The server side says hello!"))

(defn msg-broadcast []
  (map #(msg-to-client %) @clients))

;(stream/take! (first (first @clients)))
;(http/start-server app {:port 8080})

I start the Netty server with the commented out http/start-server aleph call. I also managed to fetch messages from the client via manual stream/take! call (also commented out). What I need to figure out is how to trigger this taking automatically when something comes in.

Thanks in advance for any help!

Solution

The function you're looking for is (manifold.stream/consume callback stream), which will invoke the callback for each message that comes off the stream.