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In this video, we'll get a firsthand, unobscured look at HTTP requests and responses using a command-line tool called Telnet.
Installing Telnet Client - OSX
If you're using a Mac, Telnet should be installed and enabled. Simply open a terminal and execute some of the commands used in this video.
Installing Telnet Client - Windows
Depending on your version of Windows, you may already have it installed, and you simply need to enable it. Opening PowerShell and attempting to use Telnet will reveal whether or not you'll need to install.
Try executing some of the commands we use in the video. If they aren't recognized, then you'll need to either enable or install Telnet. Here are a couple resources based on those two scenarios:
Installing Telnet Client - Linux
It's possible that Telnet is already installed and ready to use in your terminal. If not, search for instructions on your specific distribution. Depending on the package management utility you use, you may be able to install with apt-get or yum.
So that we can get the most basic,
no frills to look at HTTP,
0:00
we'll use some text-based interactions.
0:04
HTTP is a plain text protocol,
which means that messages sent using HTTP
0:07
are directly readable,
kinda like a text file on your computer.
0:11
A great piece of software to use for
this purpose is called Telnet.
0:16
Telnet is a little piece of software
that's designed for connecting to and
0:21
communicating with a remote device.
0:25
With Telnet, you aren't limited
to communicating using HTTP, but
0:27
that's what we're gonna focus on here.
0:31
Let's get started.
0:34
You can install Telnet on your
local machine if you like.
0:36
And there's plenty of instruction
out there to get you going.
0:39
Check the teacher's notes for more.
0:41
Fortunately, you also have Telnet
available to you in workspaces.
0:43
So, even though I'll be demonstrating the
work in my terminal, you'll be able to do
0:46
the same using the console on
the workspace that's linked to this video.
0:50
We'll be connecting with a web
server at httpbin.org using Telnet,
0:54
httpbin.org is a service
specifically designed for
0:59
testing HTTP requests and
seeing the resulting responses.
1:03
To connect with this server using Telnet,
I'll start by issuing the Telnet command.
1:06
Followed by the name of the host
that we wanna connect to httbin.org,
1:11
followed by the port number.
1:16
This 80 is for port 80, and indicates
a specific type of communication that will
1:18
happened with the device
we're connecting to.
1:23
In our case, the type of communication
that will be happening is HTTP messaging.
1:26
Think about this way, the host or
1:30
domain name of httpbin.org
reside at some address.
1:33
Which is the address of a specific
device or server, think of this server
1:36
is a house and it's address is called
the internet protocol or IP address.
1:41
Now, once we've arrive at the house,
let's say that there's several
1:45
people living there and
each one speaks a different language.
1:49
We only speak one language, HTTP that is.
1:51
So we'll knock on the web server's door,
which is door or port 80 by default.
1:55
As long as there's somebody in port 80,
that is,
2:00
there's a web server at this address,
we know that the person who opens the door
2:03
also speaks our language,
which again is HTTP.
2:06
Great, so I'll hit enter to connect and
then I'll send a request to get the root
2:10
using HTTP protocol version 1.1,
2:15
and follow it quickly with the host again.
2:20
And I'll hit enter twice.
2:24
A couple thing here, I have to specify
the host again because it turns out that
2:26
at this address of where we connected,
there might be several host.
2:31
For example, GoDaddy is a web host
that will put many domains or
2:35
host onto a single IP.
2:39
Listing the host again
in the httprequest.sent
2:41
allows the server to route it to
the proper place with in the server.
2:44
Another thing, I said you'll have
to quickly follow-up with the host.
2:48
I say quickly, because while using telnet,
your may timeout.
2:52
There's nothing about HTTP that requires
quickness, that's just part of Telnet.
2:56
Now, let me scroll up to where I made
this request and explain what I did.
3:01
I made a request to get or
fetch the content that is at the root.
3:06
That's why I'm using
this single slash here.
3:11
And the protocol version I'm
using of HTTP is version 1.1.
3:14
This entire line here is
called the request line.
3:19
Which we'll discuss more in just a bit.
3:22
Making this whole request is like
navigating to httpbin.org in your browser.
3:25
The response I got here is
HTML as you see down below.
3:29
And the only difference is
that when a browser sees HTML,
3:34
it's rendered by what's called
the browser's layout engine.
3:37
But here in terminal,
there's no layout engine.
3:40
In other words, the browser knows how to
read HTML and make it look presentable on
3:43
the terminal, well, the terminal is text
base so it just spits out the raw HTML.
3:46
Let's scroll down and
3:51
make another request to this server,
this time requesting a different resource.
3:52
So, to reconnect to the server,
I will telnet again to httpbin.org at 80.
3:56
And this time I will request
the resource at /xml,
4:02
again using HTTP version 1.1.
4:07
And I'll list again the host.
4:11
Press enter twice, and
there's our response.
4:14
Let's go back to this request line here.
4:19
I'm requesting the resource at /xml.
4:21
You may have used this slash notation
to refer to directories in the past.
4:25
And this sometimes the case when
communicating with web servers,
4:29
but a slash doesn't always
refer to a directory.
4:32
So be careful here.
4:35
For now, simply think of it a resource at
the address /xml on the host httpbin.org.
4:36
This resource identifier has a name,
4:45
it's called quite intuitively a uniform
resource identifier, abbreviated URI.
4:47
It's not quite the same thing as a URL,
which is a uniform resource locator.
4:53
We'll return to the similarities and
differences later on.
4:58
Now in this case, the response that
came back is XML which stands for
5:01
extensible markup language.
5:06
Instead of the response we got
previously which was HTML or
5:09
hypertext markup language.
5:12
Httpbin.org has several different
resources that it exposes for
5:15
you to test different things.
5:18
And this is one of them.
5:21
We can test HTML responses, and
we can test XML responses among others.
5:22
Now, we can't just make any request to
the server and expect a great response.
5:27
Let's scroll down and try another.
5:31
Let me clear the console here
to give myself a clean screen.
5:34
Let's again telnet to
httpbin.org at port 80,
5:39
and let's get the resource
at /treehouse using
5:43
HTTP version 1.1 and
again specifying the host.
5:48
I'm gonna hit enter twice.
5:56
And it doesn't take much scanning through
the response to see that the server's
5:57
telling us that there is no resource
that has the identifier/treehouse.
6:02
And you've probably seen this
404_NOT_FOUND message before.
6:06
Before we bring this video to a close,
6:12
let me quickly show you how
to do this in workspaces.
6:13
If you open the linked workspace,
you'll see a completely empty project.
6:16
You won't need to add any
files to the project but
6:21
you will need to use the console here.
6:24
If you don't see the console,
simply choose View, Show Console.
6:28
When the console is hidden, this option
right here will say, Show Console.
6:33
Click it and
it will come right up for you.
6:36
Now you're ready to start using Telnet.
6:41
So, just as before,
you could start by connecting with Telnet.
6:42
Telnet httpbin.org port 80.
6:46
And we could get the root
using HTTP version
6:50
1.1 at the host httpbin.org.
6:55
And there it is.
7:00
For any other work I do in the terminal,
7:02
you'll be able to do
the same in workspaces.
7:04
So the choice is yours.
7:06
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