Nov 9, 20212 min read

Node.js Server-Sent Events with Total.js framework

With the Total.js framework, you can create an HTTP route for Server-Sent Events, or you can connect easily to another server with implemented Server-Sent Events.

Route for Server-Sent Events

Server-side implementation:

exports.install = function() {
    ROUTE('GET /sse/', serversentevents, ['sse']);
};
function serversentevents() {    
    var self = this;
    var lasteventid = self.sseID || '0';
    var counter = U.parseInt(lasteventid);
    var indexer = 0;    var interval = setInterval(function() {        
    // Closes client after 10 seconds
        if (indexer++ > 10) {
            self.close();
            clearInterval(interval);
        } else {
            // Sends data to the client
            if (!self.sse({ counter: counter++, message: GUID() }, null, counter)) {
                // Something wrong
                // Client closed
                clearInterval(interval);
            }
        }    }, 1000);
}

Client-side (web browser) implementation:

var sse = new EventSource('/sse/');
sse.onmessage = function(ev) 
{
    // A message
    console.log('Message:', ev.data);
};
sse.onerror = function(e) {
    // Some error
    console.log('Error:', e);
};

Capture Server-Sent Events on the server-side

With the Total.js framework is very easy to handle messages from another server with implemented Server-Sent Events functionality. For example, the code below captures messages from another HTTP server:

var opt = {};
opt.url = 'http://127.0.0.1:8000/sse/';
opt.custom = true;
opt.headers = { accept: 'text/event-stream' };
opt.timeout = 0;
opt.callback = function(err, response) 
{    
    response.stream.on('data', U.streamer('\n\n', function(chunk) 
    {
        var lines = chunk.toString('utf8').split('\n');
        var msg = {};        // Server sent events parser
        for (var line of lines) {
            var index = line ? line.indexOf(':') : -1;
            if (index !== -1) {
                var key = line.substring(0, index);
                var val = line.substring(index + 2);
                switch (key) {
                    case 'data':
                        val = val.parseJSON();
                        break;
                    case 'retry':
                        val = +val;
                        break;
                }
                msg[key] = val;
            }
        }        
        // msg.id {String}
        // msg.data {Object}
        // msg.retry {Number}
        // msg.event {String}        
        
        console.log(msg);
    }));
};

REQUEST(opt);