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);

将打印：

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

这是因为浏览器会自动询问您在标签中看到的小图标。如果您从POSTMan，wget，curl或其他http工具发出请求，您只会看到一个请求。

Answer 2

可以使用req退出console.log(req)来追踪这一点。

查看原始请求，我们看到浏览器还为每个请求请求/ favicon。

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

Why two times the callback invoked in CreateServer of http in nodejs

2 个答案: