E.g. a client requests a webpage from a server using a HTTP request
HTTP Methods
GET
DELETE
PUT
POST
GET /index.html HTTP/1.1
Host: www.example.com
HTTP/1.1 200 OK
Date: Mon, 1 Jan 2015 22:38:34 GMT
Server: Apache/1.3.3.7 (Unix) (Red-Hat/Linux)
Last-Modified: Wed, 31 Dec 2014 23:11:55 GMT
ETag: "3f80f-1b6-3e1cb03b"
Content-Type: text/html; charset=UTF-8
Content-Length: 131
Accept-Ranges: bytes
Connection: close
<html>
<head>
<title>An Example Page</title>
</head>
<body>
Hello World
</body>
</html>
Client Request
Server Response
Status Codes
200 OK
304 Not Modified
403 Forbidden
404 Not Found
500 Internal Server Error
Node.js
Node.js
Runtime Environment
Runs on Windows, Mac OS X, Linux
Node.js applications are written in Javascript
Javascript is executed using Google V8 JS engine
V8 is written in C++ (very fast)
Single-threaded
Non-blocking IO
Non-blocking IO
Blocking Code
function exponentiate(base, index) {
var ans = base;
for (var i=1; i<index; i++) {
ans = ans * base;
}
return ans;
}
console.log(exponentiate(10, 6));
console.log("Hello World");
Non-Blocking Code with callbacks
function exponentiate(base, index, cb) {
var ans = base;
for (var i=1; i<index; i++) {
ans = ans * base;
}
cb(ans);
}
exponentiate(10, 6, function callback(ans) {
console.log(ans);
});
console.log("Hello World");
Non-blocking code allows for highly concurrent applications, allowing support for tens of thousands of concurrent connecions
