有没有一种方法可以从NodeJS触发socket.io连接事件？

Question

I'm trying some things with socket.io on NodeJS and I can't figure out how to trigger the the socket (only) from NodeJS.

Till now I was using socket.io by calling it from the front end but I wonder if is it possible to do the same thing I did on the front end but this time on the nodeJS part(server side).

My guess is it's not possible because is required a kind of connection(I like to call it a TCP connection,but I'm not sure if that's true or not) and without a second participant in the connection the socket won't work.That's my guess.

So what I'm doing now is :

app.js(server file)

 ...
 const ioLib = require('./path/io.js')(io);
 ...
 ...
 ...

path/io.js(socket file)

 module.exports = function(io){

 io.on('connection', async function(socket) {
 console.log('socket talks : a user connected');
 ...
 ...
 });

 module.exports.io = io;

 }

And from an file.ejs file I do :

var socket = io("url");

So with this,let's call it schema,I do the following :

When I access that webpage the 'connection' event is triggered in the sockets. My question is,and I'm trying to formulate it as simple as I can : How can I do the same but without a webpage?Is it possible to trigger the sockets inside the NodeJS?

What do you think?

Answer 1

It is possible to connect a Socket.IO server from a stand alone Node.js application (does not really matter where it runs) rather than a web front-end, accessed via a web browser. In order to achieve this, you should use socket.io-client . An example client usage might be as follows:

// Node.js app: client.js
const io = require('socket.io-client');
const socket = io.connect('http://SERVER_IP:SERVER_PORT', {
    reconnect: true
});

socket.on('connect', function (socket) {
    console.log('Connected to the server!');    
});

socket.emit('connected', 'Hi from the client side!');  

In this case, your server side application should include something as follows:

// Node.js app: server.js
io.on('connection', function(socket) {
   console.log('socket talks: a user connected');

   // Print the message that comes from the socket client
   socket.on('connected', function (msg) {
      console.log(msg);
   });
});   

As you can see above, fundamentally, the architecture remains the same as server-client. Now, let's go one step further and put all those codes in a single js file, and see how it works:

// server/client together: crazy-socketapp.js
const io_server = require('socket.io').listen(3030);
io_server.sockets.on('connection', function (socket) {
    console.log('A client is connected!');
    socket.on('connected', function (msg) {
        console.log(msg);
    });
});

const io_client = require('socket.io-client');
const socket = io_client.connect('http://localhost:3030', {
    reconnect: true
});

socket.on('connect', function (socket) {
    console.log('Connected to the server!');    
});

socket.emit('connected', 'Hi from the client side! ');

The output of the app:

 > A client is connected! > Connected to the server! > Hi from the client side! 

Hope this helps!