關於WebSocket的那些事兒

眾所周知傳統的http協定是客戶端（瀏覽器）發送請求，瀏覽器回應請求的方式，一條請求對應一條回應。若瀏覽器不主動請求則服務端無法想客戶端主動推資料。傳統的方式是使用AJAX輪詢（這個方式有它的問題）來解決這個問題後面展開講。

應用場景

列舉幾個應用場景：

• 網路聊天室

• 多人線上遊戲

• 網站向頁面即時推播廣告、訊息

線上實作對控制裝置的控制

#前面三個應用場景已經有很多大佬講過了，我就不講了，這裡主要簡單分析第四個應用場景。

場景4：

家裡裝有「XX」牌網路攝影機，我現在工作想看看自家「二哈」有沒有在拆家,打開改公司提供的app查看家裡的狀況，很不巧相機現在沒有開機，不過可以透過app控制相機開機，點選開機按鈕相機開機。但是相機開機需要一段時間。這時傳統的做法是透過AJAX輪詢的方式每個1秒鐘左右就向伺服器發送請求詢問設備是否準備就緒。

#########客戶端> 開機沒啊，能不能播放影片了呀。 ######

服務端> 還沒呢，別急著等會兒再來。

客戶端> 開機沒啊，能不能播放影片了呀。

服務端> 還沒呢，別急著等會兒再來。

客戶端> 開機沒啊，能不能播放影片了呀。

服務端> 還沒呢，別急著等會兒再來。

......

N次之後

#..... .

客戶端> 開機沒啊，能不能播放影片了呀。 。 。

服務端> 可以了，你可以播放了

這個看出客戶端要通過很多次詢問後，才能知道服務端什麼時候準備就緒，這樣如果發送請求的客戶特別多，請求頻率特別高這無疑會給服務端造成了不小的壓力。

如果有那麼一種方式可以讓服務端想客戶端推播訊息，就可以完美解決這個情況，於是WebSocket出現了。

WebSocket的使用

WebSocket是HTML5的新協議，所以支援HTML5的瀏覽器都能直接使用WebSocket不需要額外安裝，什麼開發包，或插件。

為了測試WebSocket我們需要簡單的搞一個服務端程式。 Node.js本身支援的協定包括TCP協定和HTTP協議，但不支援WebSocket，為了讓讓node也支援WebSocket，這裡我選用ws模組。

測試

建立一個名為testWebSocket的資料夾，使用npm init 初始化專案

設定package.json檔案加入，這裡選用ws的最新的版本

##

<span style="padding-right: 0.1px"><span class="cm-string" style="color: #aa1111">"dependencies"</span>: {</span><br/><span style="padding-right: 0.1px"><span class="cm-string cm-property">　　"ws"</span>: <span class="cm-string" style="color: #aa1111">"^6.2.1"</span></span><br/><span style="padding-right: 0.1px">}</span>

在根目錄使用npm指令npm install --save，把ws相關依賴都拉下來。

然後建立一個名為myWebSocketServer.js的文件，一個簡單的WebSocket服務端程式完成，

node myWebSocketServer.js先讓服務端跑起來。相關教學：webSocket 影片教學

<span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">// 导入WebSocket模块:</span></span><br/><span style="padding-right: 0.1px"><span class="cm-keyword" style="color: #770088">const</span> <span class="cm-def" style="color: #0000ff">WebSocket</span> <span class="cm-operator" style="color: #981a1a">=</span> <span class="cm-variable" style="color: #000000">require</span>(<span class="cm-string" style="color: #aa1111">&#39;ws&#39;</span>);</span><br/><span style="padding-right: 0.1px"><span class="cm-keyword" style="color: #770088">let</span> <span class="cm-def" style="color: #0000ff">i</span> <span class="cm-operator" style="color: #981a1a">=</span> <span class="cm-number" style="color: #116644">1</span>;</span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">// 引用Server类:</span></span><br/><span style="padding-right: 0.1px"><span class="cm-keyword" style="color: #770088">const</span> <span class="cm-def" style="color: #0000ff">WebSocketServer</span> <span class="cm-operator" style="color: #981a1a">=</span> <span class="cm-variable" style="color: #000000">WebSocket</span>.<span class="cm-property" style="color: #000000">Server</span>;</span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">// 实例化:</span></span><br/><span style="padding-right: 0.1px"><span class="cm-keyword" style="color: #770088">const</span> <span class="cm-def" style="color: #0000ff">myWs</span> <span class="cm-operator" style="color: #981a1a">=</span> <span class="cm-keyword" style="color: #770088">new</span> <span class="cm-variable" style="color: #000000">WebSocketServer</span>({</span><br/><span style="padding-right: 0.1px">    <span class="cm-property" style="color: #000000">port</span>: <span class="cm-number" style="color: #116644">8080</span></span><br/><span style="padding-right: 0.1px">});</span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px"><span class="cm-variable" style="color: #000000">myWs</span>.<span class="cm-property" style="color: #000000">on</span>(<span class="cm-string" style="color: #aa1111">&#39;connection&#39;</span>, <span class="cm-def" style="color: #0000ff">ws</span> <span class="cm-operator" style="color: #981a1a">=></span> {</span><br/><span style="padding-right: 0.1px">    <span class="cm-variable-2" style="color: #0055aa">ws</span>.<span class="cm-property" style="color: #000000">on</span>(<span class="cm-string" style="color: #aa1111">&#39;message&#39;</span>, <span class="cm-def" style="color: #0000ff">message</span> <span class="cm-operator" style="color: #981a1a">=></span> {</span><br/><span style="padding-right: 0.1px">        <span class="cm-variable" style="color: #000000">console</span>.<span class="cm-property" style="color: #000000">log</span>(<span class="cm-string" style="color: #aa1111">&#39;received: %s&#39;</span>, <span class="cm-variable-2" style="color: #0055aa">message</span>);</span><br/><span style="padding-right: 0.1px">    });</span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px">    <span class="cm-variable" style="color: #000000">setInterval</span>(() <span class="cm-operator" style="color: #981a1a">=></span> {</span><br/><span style="padding-right: 0.1px">        <span class="cm-variable-2" style="color: #0055aa">ws</span>.<span class="cm-property" style="color: #000000">send</span>(<span class="cm-string" style="color: #aa1111">&#39;Hello siegaii this is serverMessage!&#39;</span> <span class="cm-operator" style="color: #981a1a">+</span> <span class="cm-variable" style="color: #000000">i</span>);</span><br/><span style="padding-right: 0.1px">        <span class="cm-variable" style="color: #000000">i</span><span class="cm-operator" style="color: #981a1a">++</span>;</span><br/><span style="padding-right: 0.1px">    }, <span class="cm-number" style="color: #116644">1000</span>);</span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px">});</span>

用戶端

<span style="padding-right: 0.1px"><span class="cm-meta" style="color: #555555"><!DOCTYPE html></span></span><br/><span style="padding-right: 0.1px"><span class="cm-tag cm-bracket" style="color: #117700"><</span><span class="cm-tag" style="color: #117700">html</span> <span class="cm-attribute" style="color: #0000cc">lang</span>=<span class="cm-string" style="color: #aa1111">"en"</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px"><span class="cm-tag cm-bracket" style="color: #117700"><</span><span class="cm-tag" style="color: #117700">head</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px">    <span class="cm-tag cm-bracket" style="color: #117700"><</span><span class="cm-tag" style="color: #117700">meta</span> <span class="cm-attribute" style="color: #0000cc">charset</span>=<span class="cm-string" style="color: #aa1111">"UTF-8"</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px">    <span class="cm-tag cm-bracket" style="color: #117700"><</span><span class="cm-tag" style="color: #117700">title</span><span class="cm-tag cm-bracket" style="color: #117700">></span>test<span class="cm-tag cm-bracket" style="color: #117700"></</span><span class="cm-tag" style="color: #117700">title</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px"><span class="cm-tag cm-bracket" style="color: #117700"></</span><span class="cm-tag" style="color: #117700">head</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px"><span class="cm-tag cm-bracket" style="color: #117700"><</span><span class="cm-tag" style="color: #117700">body</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px"><span class="cm-tag cm-bracket" style="color: #117700"><</span><span class="cm-tag" style="color: #117700">button</span> <span class="cm-attribute" style="color: #0000cc">id</span>=<span class="cm-string" style="color: #aa1111">"test"</span><span class="cm-tag cm-bracket" style="color: #117700">></span>hello siegaii<span class="cm-tag cm-bracket" style="color: #117700"></</span><span class="cm-tag" style="color: #117700">button</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px"><span class="cm-tag cm-bracket" style="color: #117700"><</span><span class="cm-tag" style="color: #117700">script</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px">    <span class="cm-keyword" style="color: #770088">let</span> <span class="cm-def" style="color: #0000ff">ws</span> <span class="cm-operator" style="color: #981a1a">=</span> <span class="cm-keyword" style="color: #770088">new</span> <span class="cm-variable" style="color: #000000">WebSocket</span>(<span class="cm-string" style="color: #aa1111">&#39;ws://localhost:8080/testWebSocket&#39;</span>);</span><br/><span style="padding-right: 0.1px">    <span class="cm-variable" style="color: #000000">document</span>.<span class="cm-property" style="color: #000000">getElementById</span>(<span class="cm-string" style="color: #aa1111">&#39;test&#39;</span>).<span class="cm-property" style="color: #000000">addEventListener</span>(<span class="cm-string" style="color: #aa1111">&#39;click&#39;</span>, () <span class="cm-operator" style="color: #981a1a">=></span> {</span><br/><span style="padding-right: 0.1px">        <span class="cm-variable" style="color: #000000">ws</span>.<span class="cm-property" style="color: #000000">send</span>(<span class="cm-string" style="color: #aa1111">&#39;Hello Siegaii this is clientMessage!&#39;</span>);</span><br/><span style="padding-right: 0.1px">    });</span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px">    <span class="cm-comment" style="color: #aa5500">// 响应onmessage事件:</span></span><br/><span style="padding-right: 0.1px">    <span class="cm-variable" style="color: #000000">ws</span>.<span class="cm-property" style="color: #000000">onmessage</span> <span class="cm-operator" style="color: #981a1a">=</span> (<span class="cm-def" style="color: #0000ff">msg</span>) <span class="cm-operator" style="color: #981a1a">=></span> {</span><br/><span style="padding-right: 0.1px">        <span class="cm-variable" style="color: #000000">console</span>.<span class="cm-property" style="color: #000000">log</span>(<span class="cm-variable-2" style="color: #0055aa">msg</span>);</span><br/><span style="padding-right: 0.1px">    };</span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px"><span class="cm-tag cm-bracket" style="color: #117700"></</span><span class="cm-tag" style="color: #117700">script</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px"><span class="cm-tag cm-bracket" style="color: #117700"></</span><span class="cm-tag" style="color: #117700">body</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span><br/><span style="padding-right: 0.1px"><span class="cm-tag cm-bracket" style="color: #117700"></</span><span class="cm-tag" style="color: #117700">html</span><span class="cm-tag cm-bracket" style="color: #117700">></span></span>

執行結果如下

API

简单介绍下WebSocket的api

<span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">// WebSocket Api</span></span><br/><span style="padding-right: 0.1px"><span class="cm-keyword" style="color: #770088">let</span> <span class="cm-def" style="color: #0000ff">socket</span> <span class="cm-operator" style="color: #981a1a">=</span> <span class="cm-keyword" style="color: #770088">new</span> <span class="cm-variable" style="color: #000000">WebSocket</span>(<span class="cm-variable" style="color: #000000">url</span>, [<span class="cm-variable" style="color: #000000">protocol</span>] ); <span class="cm-comment" style="color: #aa5500">// 实例化一个WebSocket对象建立连接</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">/**</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">* socket的readyState属性</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">* 0 - 表示连接尚未建立。</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">* 1 - 表示连接已建立，可以进行通信。</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">* 2 - 表示连接正在进行关闭。</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">* 3 - 表示连接已经关闭或者连接不能打开。</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">*/</span></span><br/><span class="cm-tab-wrap-hack" style="padding-right: 0.1px"><span class="cm-variable" style="color: #000000">socket</span>.<span class="cm-property" style="color: #000000">readyState</span></span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">/**</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">* 只读属性 bufferedAmount 已被 send() 放入正在队列中等待传输，但是还没有发出的 UTF-8 文本字节数。</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">*/</span></span><br/><span style="padding-right: 0.1px"><span class="cm-variable" style="color: #000000">socket</span>.<span class="cm-property" style="color: #000000">bufferedAmount</span></span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">/**</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">* WebSocket 事件</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">*/</span></span><br/><span style="padding-right: 0.1px"><span class="cm-variable" style="color: #000000">socket</span>.<span class="cm-property" style="color: #000000">onopen</span>(); <span class="cm-comment" style="color: #aa5500">//连接建立时触发</span></span><br/><span style="padding-right: 0.1px"><span class="cm-variable" style="color: #000000">socket</span>.<span class="cm-property" style="color: #000000">onmessage</span>(); <span class="cm-comment" style="color: #aa5500">//客户端接收服务端数据时触发</span></span><br/><span style="padding-right: 0.1px"><span class="cm-variable" style="color: #000000">socket</span>.<span class="cm-property" style="color: #000000">onerror</span>(); <span class="cm-comment" style="color: #aa5500">//通信发生错误时触发</span></span><br/><span style="padding-right: 0.1px"><span class="cm-variable" style="color: #000000">socket</span>.<span class="cm-property" style="color: #000000">onclose</span>(); <span class="cm-comment" style="color: #aa5500">//连接关闭时触发</span></span><br/><span style="padding-right: 0.1px"></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">/**</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">* WebSocket 方法</span></span><br/><span style="padding-right: 0.1px"><span class="cm-comment" style="color: #aa5500">*/</span></span><br/><span style="padding-right: 0.1px"><span class="cm-variable" style="color: #000000">Socket</span>.<span class="cm-property" style="color: #000000">send</span>() <span class="cm-comment" style="color: #aa5500">//使用连接发送数据</span></span><br/><span style="padding-right: 0.1px"><span class="cm-variable" style="color: #000000">Socket</span>.<span class="cm-property" style="color: #000000">close</span>() <span class="cm-comment" style="color: #aa5500">//关闭连接</span></span><br/><span style="padding-right: 0.1px"><br/></span>

以上是關於WebSocket的那些事兒的詳細內容。更多資訊請關注PHP中文網其他相關文章！