http modular

What is? http modular

In a network node , Computers responsible for consuming resources , It's called a client ; The computer responsible for providing network resources to the outside world , It's called a server .
http The module is Node.js Official 、 Used to create web Module of the server . adopt http Module provided http.createServer() Method , Just
Can easily put an ordinary computer , Become a Web The server , So as to provide Web Resource service .

http Role of module

The difference between a server and an ordinary computer is , There is... Installed on the server web Server software , for example ：IIS、Apache etc. . By installing these server software ,
Can turn an ordinary computer into a web The server .
stay Node.js in , We don't need to use IIS、Apache Wait for these third parties web Server software . Because we can be based on Node.js Provided
http modular , Through a few lines of simple code , You can easily write a server software , So as to provide web service .

Server related concepts

IP Address

IP Address is the unique address of every computer on the Internet , therefore IP The address is unique . If you put “ Personal computer ” Compared to the “ A phone ”, that “IP The earth
site ” Equivalent to “ Phone number ”, Only when you know each other IP On the premise of address , To communicate with the corresponding computer .
IP Format of address ： Usually use “ dotted decimal ” Expressed as （a.b.c.d） In the form of , among ,a,b,c,d All are 0~255 A decimal integer between . for example ： use
Dotted decimal IP Address （192.168.1.1）
Be careful ：
① Every computer on the Internet Web The server , All have their own IP Address , for example ： You can Windows Running in the terminal ping www.baidu.com life
Make , You can view the of Baidu server IP Address .
② During development , Your computer is both a server , It's also a client , For testing purposes , You can enter... In your browser 127.0.0.1 This
IP Address , You can access your computer as a server .

Domain names and domain name servers

Even though IP An address can uniquely label a computer on a network , but IP The address is a long string of numbers , Is not intuitive , And it's not easy to remember , So people invented another set
Character type address scheme , The so-called domain name （Domain Name） Address .
IP Address and domain name are one-to-one correspondence , This correspondence is stored in a server called a domain name server (DNS,Domain name server) In my computer . Users
Just visit the corresponding server through a friendly domain name , The corresponding conversion is realized by the domain name server . therefore , Domain name server is to provide IP Address and domain name
Between the conversion services of the server .
Be careful ：
① Just use IP Address , Computers on the Internet can also work properly . But with the blessing of the domain name , Can make the world of the Internet more convenient .
② During development testing , 127.0.0.1 The corresponding domain name is localhost, They all represent our own computer , There is no difference in the use effect .

Port number

Port number in the computer , It's like a house number in real life . Pass the house number , Takeout boy can be in many rooms in the whole building , Accurately take out
To your hand .
Same thing , In a computer , Can run hundreds of web service . Every web Each service corresponds to a unique port number . From the client
Network request , Through port number , Can be accurately handed over to the corresponding web Service processing .
Be careful ：
① Each port number cannot be multiple at the same time web Service occupancy .
② in application ,URL Medium 80 Ports can be omitted .

Create the most basic web The server

Create a server

There are four steps to creating a server
1.- Import http modular
2.- establish web Server instance
3.- Bind to the server instance request event
4. - Start the server

req Request object

As long as the server receives the client's request , The call will pass server.on() Bound to the server request Event handler .
If you want to in the event handler , Access data or properties related to the client , You can use the following ways ：

res The response object

On the server request In the event handler , If you want to access data or properties related to the server , You can use the following ways ：

Solve the problem of Chinese garbled code

When calling res.end() Method , When sending Chinese content to the client , There will be a mess , here , You need to manually set the encoding format of the content ：
Before setting, it is shown as follows

After setting, it is shown as follows

According to url Respond to different html Content

The implementation idea is as follows
① Obtain requested url Address
② Set the default response content to 404 Not found
③ Judge whether the requested by the user is / or /index.html home page
④ Judge whether the requested by the user is /about.html About the page
⑤ Set up Content-Type Response head , Prevent Chinese miscoding
⑥ Use res.end() Respond the content to the client
according to url Address , Show different content .
The specific code is as follows

const http = require('http')
const server = http.createServer()

server.on('request', (req, res) => {
    
  // 1.  Obtain requested  url  Address 
  const url = req.url
  // 2.  Set the default response content to  404 Not found
  let content = '<h1>404 Not found!</h1>'
  // 3.  Judge whether the requested by the user is  /  or  /index.html  home page 
  // 4.  Judge whether the requested by the user is  /about.html  About the page 
  if (url === '/' || url === '/index.html') {
    
    content = '<h1> home page </h1>'
  } else if (url === '/about.html') {
    
    content = '<h1> About the page </h1>'
  }
  // 5.  Set up  Content-Type  Response head , Prevent Chinese miscoding 
  res.setHeader('Content-Type', 'text/html; charset=utf-8')
  // 6.  Use  res.end()  Respond the content to the client 
  res.end(content)
})

server.listen(80, () => {
    
  console.log('server running at http://127.0.0.1')
})

The effect is as follows