目标是允许某人实时更新在线考试的状态。（即，按激活查理的考试，更改查理斯屏幕以允许他开始参加考试。监考人之间的关系是一个监考人对许多考试。
目前，我们正在使用 sente 成功激活考试，但是一旦我们单击（激活考试）按钮，它就会继续通过路由“/chsk”一遍又一遍地发送请求。（值得称赞的是，它非常快。）在遇到以下错误之前，它成功发送了许多（10+）个这样的请求。我们认为问题出在中间件上，但是在调整包装格式以处理 websocket 请求（以及通过“/chsk”路由发送的请求之后，我们仍然收到错误。我认为问题不在于中间件，因为信息第一次通过就好了，并按预期激活了考试。我不知道为什么 sente 发送的请求不止一个。sente 正在为我们的目的工作，
我们如何确保从后端只发送一次请求？
（问题） 我一激活考试就可以冻结它，以表明 web-socket 确实做了我们想要它做的事情。
（客户端）
(ns flats.web-sockets
(:require [goog.string :as gstring]
[flats.shared :as shared]
[reagent.core :as r]
[re-frame.core :as rfc]
[taoensso.encore :as encore :refer-macros (have)]
[taoensso.sente :as sente]
[taoensso.timbre :as log :refer-macros (tracef)]))
(def ?csrf-token
(when-let [el (.getElementById js/document "token")]
(.getAttribute el "value")))
(def -chsk (r/atom nil))
(def -ch-chsk (r/atom nil))
(def -chsk-send! (r/atom nil))
(def -chsk-state (r/atom nil))
(defn sente-setup
"Takes uid (exam-id, registration-id, user-id?) to use as unique client-id"
[uid]
(let [{:keys [chsk ch-recv send-fn state]}
(sente/make-channel-socket-client! "/chsk" ; Note the same path as before
?csrf-token
{:type :auto ; e/o #{:auto :ajax :ws}
:client-id uid})]
(reset! -chsk chsk)
(reset! -ch-chsk ch-recv) ; ChannelSocket's receive channel
(reset! -chsk-send! send-fn) ; ChannelSocket's send API fn
(reset! -chsk-state state) ; Watchable, read-only atom
))
(defmulti -event-msg-handler
"Multimethod to handle Sente `event-msg`s"
:id ; Dispatch on event-id
)
(defn event-msg-handler
"Wraps `-event-msg-handler` with logging, error catching, etc."
[{:as ev-msg :keys [_id _?data _event]}]
#_(log/info (str "\nin event-msg-handler: "ev-msg))
(-event-msg-handler ev-msg))
(defmethod -event-msg-handler
:default ; Default/fallback case (no other matching handler)
[{:as _ev-msg :keys [event]}]
(tracef "Unhandled event: %s" event))
(defmethod -event-msg-handler :chsk/state
[{:as _ev-msg :keys [?data]}]
#_(log/info "In chsk/state "_ev-msg)
(let [[_old-state-map new-state-map] (have vector? ?data)]
(if (:first-open? new-state-map)
(tracef "Channel socket successfully established!: %s" new-state-map)
(tracef "Channel socket state change: %s" new-state-map))))
(defmethod -event-msg-handler :chsk/recv
[{:as _ev-msg
:keys [_?data]
[event-id {:keys [exam-status]}]
:?data}]
(log/info (str ":chsk/recv payload: " _ev-msg))
(when (= event-id :exam/status)
(rfc/dispatch [:set-current-exam-status exam-status])))
(defmethod -event-msg-handler :chsk/handshake
[{:as _ev-msg :keys [?data]}]
(let [[_?uid _?csrf-token _?handshake-data] ?data]
(tracef "Handshake: %s" ?data)))
;;;; Sente event router (our `event-msg-handler` loop)
(defonce router_ (atom nil))
(defn stop-router! [] (when-let [stop-f @router_] (stop-f)))
(defn start-router! []
(stop-router!)
(reset! router_
(sente/start-client-chsk-router!
@-ch-chsk event-msg-handler)))
（服务器端）
(ns flats.web-sockets
(:require [taoensso.timbre :as log]
[taoensso.sente :as sente]
[clojure.core.async :as async :refer [<!!]]
[taoensso.sente.server-adapters.immutant :refer (get-sch-adapter)])
(:import [java.util UUID]))
(def user-id (atom nil))
(let [chsk-server (sente/make-channel-socket-server!
(get-sch-adapter)
{:packer :edn
:user-id-fn (fn [request]
(reset! user-id (:client-id request))
(UUID/fromString (:client-id request))
#_(:client-id request)
)})
{:keys [ch-recv send-fn connected-uids
ajax-post-fn ajax-get-or-ws-handshake-fn]} chsk-server]
(def ring-ajax-post ajax-post-fn)
(def ring-ajax-get-or-ws-handshake ajax-get-or-ws-handshake-fn)
(def ch-chsk ch-recv) ; ChannelSocket's receive channel
(def chsk-send! send-fn) ; ChannelSocket's send API fn
(def connected-uids connected-uids) ; Watchable, read-only atom
)
;;;; Server>user async push
(defn broadcast!
[registration-id exam-status]
(chsk-send! registration-id
[:exam/status {:exam-status exam-status}]
5000))
（激活考试）
(defn create-exam-action
"Creates a new `exam_action` with the given `exam-id` and the `action-type`"
[{{:keys [exam-id action-type]} :path-params}]
(let [exam-id (UUID/fromString exam-id)
registration-id (dbx/READ exam-id [:registration-id])]
(exams/create-exam-action exam-id action-type)
(ws/broadcast! registration-id action-type)
(http-response/ok action-type)))
（路线）
["/chsk" {:get ws/ring-ajax-get-or-ws-handshake
:post ws/ring-ajax-post}]
*注意：一旦注册考试，我们就会启动客户端路由器，并使用考试的 ID 作为前端通道的用户 ID。