为什么两次在Node.js中的http的CreateServer中调用两次回调

Question

i am trying with following code:

const  http = require('http');
const fs = require('fs');


var hServer = http.createServer( (req, res) => {
        console.log ("Received Connection..");
        fs.readFile('./index.html', function(err, page) {
                res.writeHeader(200, {"Content-Type": "text/html"});
                res.write(page);
                res.end();

        });
});

hServer.listen(8989);

When i connect from browser http://localhost:8989 ,
I received two times the console print "Received Connection." Why?

Answer 1

const  http = require('http');
const fs = require('fs');


var hServer = http.createServer( (req, res) => {
        console.log ("Received Connection...");
        console.log('URL: ' + req.url);
        fs.readFile('./index.html', function(err, page) {
                res.writeHeader(200, {"Content-Type": "text/html"});
                res.write(page);
                res.end();

        });
});

hServer.listen(8989);

Will print:

Received Connection...
URL: /
Received Connection...
URL: /favicon

It is because the browser automatically ask for the favicon, the little icon you see in your tabs. If you fire your request from POSTMan, wget, curl, or other http tools, you'll only see one request.

Answer 2

This can be traced down by logging out req using console.log(req) .

Looking at the raw request we see that the browser additionally requests /favicon for each request.

url: '/',
url: '/favicon.ico',