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- [Instructor] Hi and
welcome back to the course.

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In this video we're going
to look at HTTP Verbs.

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HTTP is one of the most popular protocols,

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one of the most popular ways of creating

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interactions and allowing interactions

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between two internet connected elements

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such as your computer
and another computer.

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The first thing we wanna look
at is what is a web server?

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This course is all about
creating web servers, so I think

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that kinda gives you a bit of a hint.

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Now, a web server has many definitions.

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One of them is it's a piece of hardware

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like a computer is.

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Another definition is that
it is a piece of software

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and this piece of software
is designed to accept

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incoming web requests.

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Now, if this sounds like
Chinese which I hope it doesn't,

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it doesn't sound completely foreign.

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Let's have a look at what
web requests are as well.

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But first, a quick example.

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Google has many web servers.

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And whenever we go to
http://www.google.com

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in our browser, such as
Google Chrome or Safari,

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what we're doing is
we're sending something

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to one of their web servers.

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We don't know which web
server, but we know it's

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one of them.

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And when we send something
to the web server

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the web server can then
decide to respond back.

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It may not respond, as
we'll see in a moment.

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So, what is it that we
send to these web servers?

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Well, when we go to http://www.google.com

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we send exactly the
following, this is what

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the web server sees.

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So, when a user such
as ourselves, accesses

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the Google home page one
of their servers somewhere

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receives this piece of information.

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Get/http/1.1, and the
host is www.google.com.

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So, what does this mean?

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Well, this is what's
called the get request

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and the server just
sees that, get/http/1.1

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and the host name which is not here.

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So, the get is called a verb.

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It tells the server to
some extent, what we think

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the server is going to return.

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So, what is expected of the server.

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The slash is the path,
which is what we want

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out of the server.

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Finally, http/1.1 is
the protocol and this is

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the most popular http protocol, but now

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we're also experimenting
with http/2 as well

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which is a faster and
more efficient version.

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So, this is really all the server sees

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and when we create our own
web server applications

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we're going to see something very similar.

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So, what?

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Is that everything?

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Well actually, yeah.

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That's all the server sees

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and the server sees that
and then there's some code

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and the code is what the
server runs on and that allows

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it to make a decision as to
what it's going to respond with.

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So, different servers may
interpret the get request

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in many different ways and
they'll respond differently.

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For example, the server
may give you an error

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if the path is not found.

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In this case the forward slash.

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It may give you an error
if http is not supported.

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For example, if it's a mail
server and only supports

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SMTP, or if it's an FDP server and so on.

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It may give you an error if a server

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is currently unavailable.

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But, it may not also give you
errors, it may also give you

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useful stuff such as a HTML code, which is

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what it normally does at
least in Google's case.

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It may also give you some text.

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It may give you nothing if
the server is not configured

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to give you anything, then it just won't

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give you anything back.

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So, what else?

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Well, going to any page with
your browser such as Chrome

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or Safari or Firefox
will always do the same.

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It's always going to do a get request.

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So, here's a couple examples.

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For example, going to
the login on Twitter page

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which is https://twitter.com/login.

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That performs the get request get/login.

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Ad you can see, up to
the .com is the host name

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and anything after that is the path,

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what we are requesting.

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So, in this case, the host
is https://twitter.com

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and the path is /login,
which is what comes after.

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Similarly for this other
page, we are requesting

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/download/mac and you can
see that Google Chrome

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has a nice colour and it
tells us what the different

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parts are just by looking
at the colour of it.

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A lot of browers don't
do the same, which is

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a bit of a shame.

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And finally, google.co.uk, the host is

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https://www.google.co.uk and the path

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in this case is just the forward slash.

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By now you may have realised
that the forward slash

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is the root, the sort of
home page if you wish.

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And so, when we just go
to a page that normally

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just requests the home
page and then normally

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there's just a forward slash.

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So, the differences
between these three servers

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aren't just on what the
server responds with.

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Every server sees it,
essentially identical requests

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requesting different paths granted.

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But, the only difference
is what the server

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responds with and in Twitter's
case they respond with

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the Twitter login HTML page and the

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get scm case they respond with the get scm

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downloads for Mac HTML
page and in Google's case

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they respond with the
main Google home page

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which seems fairly obvious,
but really when we create

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our own web servers that's,
we're gonna see exactly

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the same as they do,
but we're gonna respond

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with slightly different HTML code.

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So, what I want you to realise is there's

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no magic going on here.

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All the server is seeing is
the piece of data coming in

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and then it's responding
with another piece of data

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and these servers all
work in the same way.

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So, what else?

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Well, going to a web page
will always do a get request.

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No matter where you go, the
server's always gonna see

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the same thing.

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That's because the browser,
such as Chrome or Safari

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is configured to do a get
request whenever it accesses

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a page, but there's also many other things

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that we can do such as,
host instead of get.

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We can do delete, we can
do put, options, head

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and there's many more actually.

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And once again, this
is just a piece of data

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that we're sending the
server and the server

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then can respond differently to each,

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but they normally have the same meaning

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for each server.

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So, all servers will
respond to a post request

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in similar ways.

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All servers will respond
with delete requests

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in similar ways.

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In the same way that all
servers respond to a get request

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in a similar way.

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That's because these
things are so widely used

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that they have nearly
become a standard now.

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So, the crux of this
lesson is the HTTP Verbs.

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So, here's what they normally
mean, which doesn't mean

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that they will always mean
this, but it does mean

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that this is a fairly common meaning.

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So, for the get normally
means to retrieve something.

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For example, when you go
to the Google home page

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you're retrieving the Google home page.

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In the case of an API
you may do something like

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get/item/1 and that presumably retrieves

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an item identified by 1.

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So, one may be the item's
ID or something like that.

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You nay do a post, which
for the server means

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receive data and use it,
doesn't really tell you how

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it's gonna use it, but
presumably if you do post/item

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that may create a new item see.

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Also, when you do a post request normally

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you have to send some data
along the post request.

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We're gonna look at how to do that

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and basically in this case
may be a piece of Jason

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which is name and prize
and then presumably

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the server would create an item called

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chair with price 9.99, presumably

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and we don't know unless
we look at the code.

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A put request means, make
sure that something is there.

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Notice how it doesn't say create things

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or do anything, it just makes
sure that something is there.

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So if you do put/item
with some data again,

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that may create a new chain to make sure

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that the chair exists.

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Or, if the chair's already
there, it may update

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the chair, change the price.

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Again, to make sure
whether that item is there,

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but unless the put request
allows for duplication

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then that's what it'll do.

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First it'll create it
and then will update it.

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And finally, we can also
do delete, which tends

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to mean remove something
such as delete/item/1

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and presumably that would delete the item

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with ID number one.

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Now, we've looked at four
of the most important

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HTTP Verbs, but there
are many others and we

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won't be looking at those in this course,

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but nevertheless, it's worth knowing

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that there are other types of HTTP Verbs

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that we can use.

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So, that's everything for this video.

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I wanted to introduce you
to the concept of the way

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the web works and how
these HTTP Verbs behave

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because in the next video we're gonna look

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at HTTP, sorry, at rest
APIs and these verbs

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are gonna come in really handy there.

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So, without further adieu, I'll see you

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in the very next video.