[FFH] websocket practice of real-time chat room

Preface

If you want to realize the same function as wechat chat , It is obviously not enough to communicate within the network , Therefore, the soft bus does not work with this kind of long-distance transmission . If we want to complete the chat function of wechat , The traditional method is to use webSocket Full duplex communication with the help of server .

WebSocket What is it? ？

WebSocket yes One in a single TCP Network communication protocol for full duplex communication on the connection .

There was no such thing as webSocket When , We all use HTTP Protocol for network communication , however HTTP The protocol is a stateless , There is no connection , One-way application layer protocol , Therefore, the client can only make one-way requests to the server , The server cannot actively send messages to the client , As a result, it is difficult for businesses such as real-time chat to carry out .

Developers can use HTTP The scheme of long polling , That is to say, we need HTTP The connection request must be maintained for a period of time , To get the latest server messages . This is obviously inefficient , And it's a waste of resources .

So it was born WebSocket, You only need to connect once , You can always maintain full duplex communication .

Demo Exhibition

Now let's use the official WebSocket Interface to achieve a simple real-time chat room Demo. The effect is as follows ：

Code implementation

You can see the interface description in the official document , We only need a few interfaces to realize our business requirements .

https://developer.harmonyos.com/cn/docs/documentation/doc-guides/websocket-connection-0000001333321005

① Apply for network permission

stay config.json Register network permissions in the file , This permission allows the program to open a network socket , Make a network connection .

"reqPermissions": [
  {
    "name": "ohos.permission.INTERNET"
  }
]

② Import webSocket modular

import webSocket from '@ohos.net.webSocket';

③ establish webSocket object

Then we call createWebSocket() Interface generates a webSocket object , And save it .

let ws = webSocket.createWebSocket();

④ Connect webSocket passageway

call connect() Interface . I need a URL Pass in as a parameter , In this demo in , Directly use a previously developed server interface to call , But not open to the outside world , Therefore, you only need to put the interface address you have developed into ”wsURL“ Inside you can .

    onInit() {
    
        let that = this;
        ws.connect("wsURL", (err, value) => {
    
            if (!err) {
    
                console.log("xxx---connect success");
            } else {
    
                console.log("xxx---connect fail, err:" + JSON.stringify(err));
            }
        });
    },

⑤ Subscribe to message updates in the channel

Here we call on( type:‘message’ ) Interface for message listening , It should be noted here that the string type passed by the server , So if the message is JSON object , You need to use JSON.parse() To analyze , restore JSON object .

    onInit() {
    
        let that = this;
        ws.on('message', (err, value) => {
    
            console.log("xxx---on message, message:" + value);
            // What is passed is the serialized string , Need to deserialize as JSON object 
            let dataObj = JSON.parse(value)
            console.log("xxx---parse success---postId: "+dataObj.postId+",message:"+dataObj.message)
            that.message.push(dataObj)
            console.log("xxx---check message: "+JSON.stringify(that.message))
        });
    },

⑥ Send a message

Next call send() Interface to send messages , Note here , If you want to pass JSON object , To use JSON.stringify() Do serialization , Make sure we pass in the form of a stream string .

In the callback of this interface , We can also print it out , Check whether the message is sent successfully .

   	sendMessage(){
    
        let that  = this;
        let data = {
    
            postId:that.id,
            message:that.sendMes
        }
        let dataStr = JSON.stringify(data)
        ws.send(dataStr, (err, value) => {
    
            if (!err) {
    
                console.log("xxx---send success");
            } else {
    
                console.log("xxx---send fail, err:" + JSON.stringify(err));
            }
        });
        that.message.push(data)
    },

⑦ Hide the title bar

Careful friends will find , my demo The black title bar of the display is missing , In fact, it can be hidden , Only need config.json In file module.abilities Add a few lines of code below .

"metaData":{
    
            "customizeData":[
              {
    
                "name": "hwc-theme",
                "value": "androidhwext:style/Theme.Emui.NoTitleBar",
                "extra":""
              }
            ]
          }

⑧ Pattern design

Next, simply design the interface style , Render the obtained message .

<div class="container">
    <div style="width: 100%;height: 8%;color: #ff86868a;font-size: 25px;justify-content: center;position: absolute;">
        <text style="top: 10px;">
             Real time chat room 
        </text>
    </div>
    <list style="height: 80%;">
        <list-item for="{
     {message}}" class="{
     {$item.postId==id?'listItemRight':'listItemLeft'}}" >
            <div class="listItemDiv" >
                <text style="padding:5px;border-radius: 10px;font-size: 20px;margin: 5px;max-width: 70%;">
                    {
   {$item.message}}
                </text>
            </div>
        </list-item>
    </list>
    <div style="position: absolute;left:10px;bottom: 20px;">

        <textarea id="textarea" class="textarea" extend="true" placeholder=" Please input chat information " onchange="inputChange" >
        </textarea>
        <button style="width: 75px;height: 50px;margin-left: 10px;background-color: #ff4848f5;" onclick="sendMessage">   send out  </button>
    </div>

</div>

.container {
    
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    left: 0px;
    top: 0px;
    width: 100%;
    height: 100%;
}
.textarea {
    
    placeholder-color: gray;
    width: 70%;
}

.listItemDiv{
    
    background-color: #ff87f3d0;
    border-radius: 10px;

}

.listItemLeft{
    
    margin: 10px;
    width: 100%;
    justify-content: flex-start;
}
.listItemRight{
    
    margin: 10px;
    width: 100%;
    justify-content: flex-end;
}