PHP curl sending message to Node.js returns no result

Question

I wanted to implement websockets to a complex web system to synchronize data properly. The idea was that all clients may make ajax-calls, php handles those calls, may edit data on a database and on success the php-backend sends some data to a websocket-server. That websocket server then sends the data to all subscribed clients, which may be interested in the data.

So far clients can subscribe to the websocket server (socket.io) but I can't figure out how to make php send messages to the websocket server.

So far my websocket server looks like this:

const fs = require('fs');

const credentials = {
  key: fs.readFileSync('C:/xampp/apache/conf/ssl.key/server.key'),
  cert: fs.readFileSync('C:/xampp/apache/conf/ssl.crt/server.crt')
};
const app = require('express')();



// var server = require('https').Server(app);
let server = require('https').createServer(credentials, app);
let io = require('socket.io')(server);

server.listen(3000);

io.sockets.on('connection', function(socket){
    console.log("connected");
    socket.emit('test', { hello: 'world' });
    socket.on('some other event', function (data) {
        console.log(data);
    });

    socket.on('subscribe', function(room) {
        console.log('joining room', room);
        socket.join(room);
    });

    socket.on('unsubscribe', function(room) {
        console.log('leaving room', room);
        socket.leave(room);
    });

    socket.on('send', function(data) {
        console.log('sending message');
        io.sockets.in(data.room).emit('message', data);
    });
});

And my php-calls look like this:

require_once __DIR__.'/../vendor/autoload.php';
$dbHandler = \services\DBHandling::getInstance();


$data = [
    "subscribe" => "room3",
    "message" => "evacuate nuclear reactor block B !"
];
$data_string = json_encode($data);

$curl = curl_init("http://localhost");

curl_setopt($curl, CURLOPT_HEADER, true);
curl_setopt($curl, CURLOPT_HTTPHEADER,['Content-Type: application/json',
    'Content-Length: ' . strlen($data_string)
]);

curl_setopt($curl,CURLOPT_PORT, 3000);
curl_setopt($curl,CURLOPT_POST,true);
curl_setopt($curl,CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($curl,CURLOPT_FOLLOWLOCATION, 1);
curl_setopt($curl,CURLOPT_CONNECTTIMEOUT, 2);
curl_setopt($curl,CURLOPT_SSL_VERIFYHOST, 0);
curl_setopt($curl,CURLOPT_RETURNTRANSFER,true);
curl_setopt($curl,CURLOPT_POSTFIELDS,$data_string);

$json_response = curl_exec($curl);
$status = curl_getinfo($curl, CURLINFO_HTTP_CODE);

if ($status != 200) {
    print_r([
        'Error',
        $status,
        curl_errno($curl)
    ]);
}
curl_close($curl);

The php-backend only needs to send messages to the websocket server and doesn't need to receive any.

Answer 1

You could make your php and your node communicate over HTTP.

You already have express installed in your node application so let's define a little API

Define a middleware to ensure that is your php calling the node API

/** 
 *  Secure the HTTP calls from PHP
 *  Return a 403 (forbidden) if no token given
 * */
app.use(function (req, res, next) {
    // Do your logic to secure your API if your node application is visible from the internet
    // You don't want malicious people to send event as your php ;)
    if(false) {
        res.sendStatus(403);
        return;
    }

    next(); // it's ok let the process continue
});

Define a simple route that answer on GET http://localhost:3000/your/endpoint

app.get('/your/endpoint', function(req, res) {
    io.sockets.emit('update');

    res.sendStatus(200);
});

If you want to use the body of the HTTP request, you could use library like body-parser that allow you to do stuff like below. This route answer at POST http://localhost:3000/post/example

/** Enable the parsing of request body */
app.use(bodyParser.json());

app.post('/post/example', function(req, res) {
    let body  = req.body,
        event = body.event,
        data  = body.data || {};

    if(undefined === event) {
        res.sendStatus(400);
        return;
    }
   ...
}

Answer 2

WebSocket is a complex protocol that you will not be able to use with raw PHP. Here are some links, just for information:

• https://developer.mozilla.org/en-US/docs/Web/API/WebSockets_API/Writing_WebSocket_servers
• https://tools.ietf.org/html/rfc6455

---

If you want a communication between your PHP and WebSocket server, then you can use a PHP library that helps you in that way. Here is a little list of known PHP library that do the job:

• https://github.com/amphp/websocket-client
• https://github.com/Nekland/Woketo
• https://github.com/ratchetphp/Ratchet

For more information, please checkout their documentation.