NodeJS #3期：Node Stream Complete Guide Notes

Networking、Servers、and Clients 🔗︎

networking 🔗︎

servers and clients 🔗︎

Any networked computer can be a server
Any networked computer can be a client

tiny chunks of data
For example, if we have a payload:

This is the message we want to send. It contains information. XXX SFDSDF sdafEFAEFwqf

it might get broken up into multiple packets tcp vs udp

TCP - reliable transport : if a packet is not acknowledged(ACK) on the other end, it get resent UDP - unreliable transport: packets are sent but there is no confirmation that the packet was received at the other end

tcp vs udp uses UDP - sometimes used for streaming video and audio, some games TCP - everything else

protocols the language that computer programs speak to each other Exmaples of network protocols

• HTTP - browse web pages
• HTTPS - browse web pages with encryption
• SMTP - send and receive emails
• IMAP, POP3 - load emails from an inbox
• IRC - chat
• FTP - file transfer
• SSH - remote shell over an encrypted connecton
• SSL - low-level secure data transfer(used by HTTPS)

Stream Types stream types There are many kinds of streams. We’ve seen two types already: transform(through2) and writable(concat - stream)

• readable - produces data: you can pipe FROM it
• writable - consumes data: you can pipe TO it
• transform - consumes data, producing transformed data
• duplex - consumes data separately from producing data

stream stypes in code

• readable: readable.pipe(A)
• writable: A.pipe(writable)
• transform: A.pipe(transform).pipe(B)
• duplex: A.pipe(duplex).pipe(A)

readable stream methods

• stream.pipe(...)
• stream.once('end', function() {}) you probably won’t need to call these very oftern:
• stream.read()
• stream.on('readable', function() {} ) you can let a module or .pipe() take care of calling those

example:

var fs = require('fs')
var r = fs.createReadStream()
r.pipe(process.stdout)

writable stream methods .pipe() which is a method of all readable streams(readable, transform, and duplex).

Any stream you can write to (writable, transform, and duplex streams) has these methods:

• .write(buf)
• .end()
• .end(buf)
• .on('finish', function() {})
• .once('finish', function() {})
• (…).pipe(stream)

example:

const fs = require('fs');
const w = fs.createWriteStream('cool.txt`)
w.write('hi\n');
w.write('wow\n');
w.end();

readable : paused mode default behavior with automatic backpressure

readable: flowing mode data is consumed as soon as chunks are available (no backpressure) turn on flowing mode with:

• stream.resume()
• stream.on('data', function(buf) {})

core streams http core streams

// req: readable, res: writable
http.createServer(function(req, res) {})

// req: writable, res: readable
var req = http.request(opts, function(res) {} )

example: http-server.js:

var http = require('http')
var fs = require('fs')
var server = http.createServer(function(req, res) {
    if(req.method == 'POST') {
       req.pipe(process.stdout)
       req.once('end', function() {
            res.end('ok\n')
       })       
    }
  else  {
    res.setHeader('content-type', 'text/plain')
    fs.createReadStream('hello.txt').pipe(res)
  }
})

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