Node. Js Http modules

Http module, the main application is two parts:

Http.createserver acts as a Web server
Http. createClient, which acts as a client and implements crawlers and the like.

The Http server

Create a simple HTTP server

The Nodejs website provides the following example code:

const http = require('http')

const hostname = '127.0.0.1'
const port = 3000

const server = http.createServer((req, res) = > {
  res.statusCode = 200
  res.setHeader('Content-Type'.'text/plain') //writeHead, 200 indicates that the page is normal, and text/plain indicates that the page is text.
  res.end('Hello World\n') // end completes the write
})

server.listen(port, hostname, () = > {
  console.log(The server runs in http://${hostname}:${port}`)})Copy the code

Analyze the code:

First of all, throughrequire('http')The introduction ofhttpThe module.
And then, throughhttp.createServer([requestListener])To create a Web server and pass in an optional callback function with two parameters representing the client request objectrequestAnd the server-side response objectresponse.
Finally, useserver.listen([port][, hostname][, backlog][, callback]), start at the specifiedportandhostnameThe accepthttpRequest and respond

Through the above three steps, you have created a simple HTTP server.

Shut down the server

How do I shut down the HTTP server I just created?

// Stop the server from receiving new connections
server.close([callback]) 
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timeout

The Node.js Http module also provides server.timeout for viewing or setting a timeout

server.timeout = 1000 // Set the timeout to 1 second
console.log(server.timeout)
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The request object

Request. url: Indicates the URL requested by the client
Request. headers: HTTP header requested by the client
Request. Method Indicates the method of obtaining a request. There are several options, such as POST,GET, and DELETE.
Request. HttpVersion: Indicates the HTTP version
Request. Trailers, for some additional HTTP headers
Request. socket, the socket object used to listen for client requests

We can write a simple JS code to record the client request information. Create a file named simpleHttpServer.js that might look like this:

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

const server = http.createServer((req, res) = > { 
  res.statusCode = 200
  res.setHeader('Content-Type'.'text/plain')
  if(req.url === '/') {let logfile = fs.createWriteStream('./log.txt') 
      logfile.write('Request method:${req.method} \r\n`)
      logfile.write('Request URL:${req.url} \r\n`)
      logfile.write('Request header object:The ${JSON.stringify(req.headers, null.4)} \r\n`)
      logfile.write('Request HTTP version:${req.httpVersion} \r\n`)      
  }
  res.end('Hello World\r\n')
})

server.listen(3000.'127.0.0.1'.() = > {
  console.log('Server running at http://127.0.0.1:3000')})Copy the code

The contents of log.txt might look like this:

GET request URL: / Request header object: {"host": "localhost:3000", "connection": "keep-alive", "upset-insecure -requests": "1", "user-agent": "Mozilla/5.0 (Windows NT 6.1; Win64; X64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36", "Accept ": "text/html,application/xhtml+xml,application/xml; Q = 0.9, image/webp image/apng, * / *; Q = 0.8, application/signed - exchange; v=b3", "accept-encoding": "gzip, deflate, br", "accept-language": "zh-CN,zh; Q = 0.9 ", "cookie", "Webstorm - ab681485 = f7ada1cf - 810 - b - 404 - b - 9211-5 cd0460e5013; OptimizelyEndUserId = oeu1506523580880r0. 9072636112603187; _ga = GA1.1.744315833.1506431133 "} requests HTTP version: 1.1Copy the code

The response object

response.writeHead(statusCode, [reasonPhrase], [headers])
Response. statusCode, the HTML page status value
Response. header, the HTTP header returned, can be either a string or an object
Response.settimeout (msecs, callback) : Sets the time to be returned by HTTP timeout. Once the time is exceeded, the connection will be discarded
Response. statusCode, set the returned page statusCode
Responsetheader (name, value), which sets the HTTP header
Response. headersSent checks whether the HTTP header is set
Response.write (chunk, [encoding]), the returned web page data, [encoding] the default is UTF-8
Response.end ([data], [encoding]), the response ends

URL parsing

In Node.js, a URL module and a QueryString module are provided

The QueryString module is used for URL processing and parsing

querystring.parse(str, [sep], [eq], [options])

Such as:

querystring.parse('foo=bar&baz=qux&baz=quux&corge')
// returns
{ foo: 'bar'.baz: ['qux'.'quux'].corge: ' ' }
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querystring.stringify(obj,separator,eq,options)

This method serializes an object into a string, as opposed to QueryString.parse. Such as:

querystring.stringify({name: 'whitemu'.sex: [ 'man'.'women']});// returns
'name=whitemu&sex=man&sex=women'
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URL form

The URL module provides utility functions for URL handling and parsing. A URL string is a structured string that contains multiple meaningful parts. When parsed, a URL object is returned that contains each component as an attribute.

The following details describe each component of a parsed URL

Format (urlObject) returns a url string formatted from urlObject
Url.parse (urlString[, parseQueryString[, slashesDenoteHost]]), parses a URL string and returns a URL object

We can use the object parsed by url.parse() to get the individual values in the URL

For more information, please refer to Nodejs Chinese official website

Build a simple HTTP JSON API Server

Write an HTTP server that responds to JSON data every time it receives a GET request with the path ‘/ API /parsetime’. We expect the request to contain a query parameter (Query String) with the key being “ISO” and the value being the ISO time.

url: /api/parsetime? Iso = 2017-04-05 T12:10:15. 474 z

The JSON response should contain only three attributes: ‘hour’, ‘minute’, and ‘second’. Such as:

{
  "hour":21."minute":45."second":30
}
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url: /api/unixtime? Iso = 2017-04-05 T12:10:15. 474 z, its return will contain an attribute: ‘unixtime’, the corresponding value is a UNIX timestamp. Such as:

  { "unixtime": 1376136615474 }
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The actual code might look like this:

const http = require('http')
const url = require('url')

const hostname = '127.0.0.1'
const port = 3000

/ * * *@desc: Parsing time *@param {Object} Time, date object *@return {Object}* /
function parsetime(time) {
    return {
        hour: time.getHours(),
        minute: time.getMinutes(),
        second: time.getSeconds()
    }
}

/ * * *@desc: Unix time *@return {Object}* /
function unixtime(time) {
    return { unixtime: time.getTime() }
}

const server = http.createServer((req, res) = > {
    let parsedUrl = url.parse(req.url, true)
    let time = new Date(parsedUrl.query.iso)
    let result
	  // Home page, return the current time json
    if(req.url=='/'){
        result = parsetime(new Date()}// Return json of the query time
    else if (/^\/api\/parsetime/.test(req.url)) {
        result = parsetime(time)
    }
    // Return unixtime of the query time
    else if (/^\/api\/unixtime/.test(req.url)) {
        result = unixtime(time)
    }

    if (result) {
        res.writeHead(200, { 'Content-Type': 'application/json' })
        res.end(JSON.stringify(result))
    } else {
        res.writeHead(404)
        res.end()
    }
})

server.listen(port, hostname, () = > {
    console.log(The server runs in http://${hostname}:${port}`)})Copy the code

The Http client

In Node.js, you can easily request data from other sites using the Request method or http.get(options[, callback]).

http.request(options, callback)

The options argument to the request method can be either an object or a string. If it’s a string, it means it’s a URL, and Node automatically calls url.parse() to handle this argument.

Http.request () returns an instance of the http.ClientRequest class. It is a writable data stream, and if you want to send a file via POST, you can write the file to this ClientRequest object

Now let’s try www.github.com

const http = require('http')
let options = {
    hostname: 'www.example.com'.port: 80.path: '/'.method: 'GET'
}

const req = http.request(options, (res) = > {
    console.log(`STATUS: ${res.statusCode}`) // Return the status code
    console.log(`HEADERS: The ${JSON.stringify(res.headers, null.4)}`) // return to the head
    res.setEncoding('utf8') // Set the encoding
    res.on('data'.(chunk) = > { // Listen for the 'data' event
        console.log(` subject:${chunk}`)
    })

})
req.end() // the end method ends the request
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Here we request the information on the website, based on which we can develop more useful crawlers and extract useful information. If you are interested, you can also study further.

Commonly used NodeJS NPM package

Express is a concise and flexible Node.js Web application framework that provides a series of powerful features to help you create a variety of Web applications, as well as rich HTTP tools. Chinese website
Koa, koA is a new Web framework, built by the same people behind Express, that aims to be a smaller, more expressive, and more robust cornerstone of web application and API development. By making use of async functions, Koa helps you discard callback functions and greatly enhances error handling. Chinese website
Request, the request module makes HTTP requests much simpler

Node.js Http module