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>> SPEAKER 1: All right, let's take a
look at how the staff solution actually

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operates, so that you
get a sense, first off

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how the web server's supposed
to run, and how you can actually

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get it running on your own computer.

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So picture it here.

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I've already installed in CS50 ID
pset6 dot zip, per the specification.

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I've unzipped it, and I've
CDed into my pset6 directory.

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One of the first things you're
going to want to do, especially

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if you've been using a CS50 IDE to play
along with recent lectures, wherein

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we've been using PHP in
CS50 IDE, specifically,

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using that web server called Apache,
whereby you can start and stop it

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with that command, Apache 50.

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First, go ahead and
type "Apache 50 stop"

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just to make sure that if you were
following along in recent days,

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and you turned on Apache, you're
turning it off in this way

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by stopping the server.

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Now, what I'm going to do is exactly
what the spec tells me to do.

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I'm going to go to tilda CS50 slash
pset6 slash server, and just hit Enter.

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You'll notice that I'm yelled at
with some usage information, whereby

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I should be running
the program as server

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with an optional dash p and then a
port number, which you can actually

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leave blank because by
default, per the spec,

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the web server is going to
assume that you want port 8080.

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Meanwhile, you might recall that
port 8080 is not really standard,

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rather port 80 is the
number we've talked

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about being the default for HTTP.

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Well, turns out that CS50 IDE
is simply configured in a way,

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such that when you with a browser try
to visit port 80 from the outside world,

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it's going to sort of magically
port forward, or redirect itself,

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to port 8080 inside
of your server itself.

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>> So the last thing here is the command
line argument, the path to route.

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And by that I just
mean, what folder do I

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want to tell the server
to use to serve up files?

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In other words, if the user visits
slash, what should he or she see?

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Well, let's go ahead and
run exactly that again,

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this time specifying that I
want the root of my web server

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to be the public directory, that comes
with problem set six distribution code.

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When I hit Enter, you'll see
in yellow here, a reminder

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as to what folder I'm actually using.

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In this case, it's a long string,
"home ubuntu workspace pset6 public."

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And that last word is what's key.

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And then lastly, apparently, my
server's now listening on port 8080.

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>> What I'm next going to do is recall that
in CS50 ID in the top right hand corner

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of your screen, you're going to see
a URL that is ide50-username.cs50.io.

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And indeed, if you click
that, you'll be whisked away

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to another browser tab,
that, in this case,

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is going to show me the contents
of my web servers roots.

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In other words, the files you see here,
cat dot HTML, cat dot JPEG, favicon dot

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ico, hello dot HTML,
hello dot php, and test,

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are all of the same
contents that you would see

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with LS inside of my public directory.

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And what's nice is that if I go
ahead and click now on cat dot HTML,

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I see cat dot HTML.

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And if I click on cat dot
JPEG, or hello dot HTML,

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or even type in my name David,
and then click "say hello,"

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you'll see that all of the
files work because the staff

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solution, of course, installed
in CS50 ID is fully functional.

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So it works exactly as your own
solution should ultimately work.

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>> Meanwhile, if we go back to my terminal
window, where I ran the server command,

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notice what the console has been saying.

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I see here that the first request that
I received was literally get slash cat

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dot HTML, HTTP version 1.1.

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And then, in green what
the staff solution has done

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is it's showing me the
first line of output

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that the web server is responding with.

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In other words, we've
already written the code

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that opens up that virtual envelope,
containing that get request.

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And then we respond to the
user but, simultaneously,

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print to the output screen
here HTTP 1.1, 200 OK

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to confirm what we're putting in
the return envelope, so to speak,

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that we're sending back to the user.

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>> And so what's going on here is
that in the terminal window,

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we're running the web
server, and, therefore, it's

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listening for HTTP
requests on TCP port 8080.

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Meanwhile, in my web browser,
as I click through each

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of those files, or even input my
name David, and then click Submit,

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that is my browser
talking to the web server.

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And what the web server's doing,
then, in that terminal window

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is showing me exactly
the first line that's

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been received in a virtual
envelope and exactly

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the first line that's being
responded with to that web client.