Note that in this example, we don’t have to specify encoding:
rs
is simply piping bytes
from stream.txt to
ws
(which is writing them to stream_copy.txt); encoding only mat‐
ters if we’re trying to interpret the data.
Piping is a common technique for moving data. For example, you could pipe the con‐
tents of a file to a webserver’s response. Or you could pipe compressed data into a
decompression engine, which would in turn pipe data out to a file writer.
Web Servers
While Node is being used in many applications now, its original purpose was to pro‐
vide a web server, so we would be remiss not to cover this usage.
Those of you who have configured Apache—or IIS, or any other web server—may be
startled at how easy it is to create a functioning web server. The
http
module (and its
secure counterpart, the
https
module) exposes a
createServer
method that creates a
basic web server. All you have to do is provide a callback function that will handle
incoming requests. To start the server, you simply call its
listen
method and give it a
port:
const
http
=
require
(
'http'
);
const
server
=
http
.
createServer
(
function
(
req
,
res
) {
console.log(
`
${
req
.
method
}
${
req
.
url
}
`
);
res
.
end
(
'Hello world!'
);
});
const
port
=
8080
;
server
.
listen
(
port
,
function
() {
// you can pass a callback to listen that lets you know
// the server has started
console.log(
`server startd on port
${
port
}
`
);
});
Most operating systems prevent you from listening on the default
HTTP port (80) without elevated privileges, for security reasons.
As a matter of fact, you need elevated privileges to listen on any
port below 1024. Of course this is easy to do: if you have sudo
access, you can just run your server with sudo to gain elevated
privileges, and listen on port 80 (as long as nothing else is). For
development and testing purposes, it’s common to listen on ports
above 1024. Numbers like 3000, 8000, 3030, and 8080 are com‐
monly picked because they are memorable.
If you run this program and visit
Hello
world!
. On the console, we’re logging all requests, which consist of a method (some‐
Web Servers | 297
