From simple to deep - websocket

Websocket Introduce

Websocket It's a protocol , And http The agreement is similar to , These two protocols are used for communication between client and server .
however ,Websocket And http There is a difference .

That we use a lot http Communication with the server is limited , The server cannot actively send data to the client .

The client sends the request , Server responds to requests , The server cannot actively send data to the customer .

websocket The server can actively communicate with the client

websocket Use

Just looking at the introduction of theory can not better understand websocket.

websocket The protocol is precisely because the server can actively send information to the client , So it is used more in chat applications .
Of course http Chat applications can also be implemented , That's using polling .

polling —— The client sends requests to the server every once in a while , The client can get the latest data from the server in real time .

---

1、 establish websocket object ( important , Must be created first websocket object )

let ws=new WebSocket(" Fill in the server-side execution websocket Application path ");// for example ：ws://127.0.0.1:8111
// You can see on the agreement that http Differences in requests .

2、 Execute when the client establishes a link with the server ——open event

ws.addEventListener("open",()=>{
    
	console.log(" Link to the server ");
});

3、 Client sends message ——send event

ws.send(" Hello , The server ");// Use send You can send information to the server 

4、 The client receives messages sent by the server ——message event

ws.addEventListener("message",(content)=>{
    
	console.log("content It is the message sent from the server ："+content);
})

5、 The client actively closes the link with the server ——close event

ws.close();// The client actively closes the link with the server 

6、 After the client closes the link with the server, execute ——close event

ws.addEventListener("close",()=>{
    
	console.log(" The callback is executed after the client closes the link ");
});

7、 Abnormal link between client and server ——error event

ws.addEventListener("error",(err)=>{
    
	console.log(err);
});

error The thing to note about the incident is , When the link is abnormal , Will execute error event , however close Events will also be triggered .

Generalization ：

websocket event	Introduce
open	Client and server link
send	The client actively sends information to the server
message	The client receives messages from the server
close	The client actively closes the link with the server
close	Execute when the client and server close the link
error	Abnormal link between client and server

Tips:
The server-side small series uses node.js More , So create websocket The application module is called ：nodejs-websocket