In this course, you'll explore the basic structure of a web application, and how a web browser interacts with a web server. You'll be introduced to the request/response cycle, including GET/POST/Redirect. You'll also gain an introductory understanding of Hypertext Markup Language (HTML), as well as the basic syntax and data structures of the PHP language, variables, logic, iteration, arrays, error handling, and superglobal variables, among other elements. An introduction to Cascading Style Sheets (CSS) will allow you to style markup for webpages. Lastly, you'll gain the skills and knowledge to install and use an integrated PHP/MySQL environment like XAMPP or MAMP.
Macintosh: Using NGrok with the Autograder
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From the course by University of Michigan
Building Web Applications in PHP
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From the lesson
PHP Arrays
We look at unique aspects of arrays in the PHP language.
Meet the Instructors
Charles SeveranceProfessor
School of Information
Hello and welcome to Web Applications for Everybody.
Today we're going to learn a little bit about ngrok.
ngrok is a way that we can get our assignments autograded, and
perhaps you are in the lesson where
we're doing this grading of the guessing game.
We're grading the guessing game.
We have to put some code here, and the problem here is that we have to have this
code running on out laptop, because this server is on the real Internet and
it can't talk to your laptop, and so what I've got is I've got some code
running here, and that's in my Application/MAMP/htdocs/assn,
sub guess, sub broken.php, and so, I'm running MAMP.
So, that code right there is the same as what I am seeing here,
and so if I type guess, you know I can say, guess =42.
Well or I get missing guess parameter, and our guess=42.
Yeah, I'm right.
Okay, so the problem is if I just take this URL and I put it in the guessing
game, I mean if I put it in the autograder, this autograder is running out
there in the Internet somewhere and it can't connect to local host,
because your local host is not also on the Internet, so we have to find a way.
So this is going to blow up really badly, and it shows you something about the test.
When things blow up, you start to look from the bottom up,
and look for toggle, and this, it looks icky.
You have to read it.
This looks like it might be like a bug, but it's not,
it is a, it can't connect to port 8888.
Connection refused, this URL.
But don't just assumed that the autograder's blown-up,
sometimes the autograder like gets an error, and it shows you what it is, and
it tried to retrieve your file and it couldn't.
So something went wrong, okay?
So that's the problem.
We've gotta get to the point where we can't use this local host URL.
But as I've said, there is this wonderful piece of software called Ngrok, and
what Ngrok does basically is it makes it so
that anyone on the real Internet can talk to you laptop.
So over here, is where the server is.
This is where your MAMP is.
This is you and your, right?
So you're running MAMP over here.
MAMP over there, and this is the autograder right here.
The autograder cannot talk to your local host.
It can't do that, that doesn't work, but you can run a piece of software
that effectively exports your local host to this place called ngrok.com and
then the autograder can talk to that, and I'm going to show you how to do that.
Now to get this to work, you gotta download some software.
So let's do that.
Let's go to Download.
Now it's different from Mac, and different from Windows.
So I'm going to download it, and it does, it's a pretty small piece of code, and
I'm going to put this in, it's going to be in my downloads folder.
Where's the downloads folder?
There's the downloads folder, and it's a zip file.
There might be different install processes for Windows, but
you'll get a point here where you have this ngrok running.
Okay, so we have this running on local host and we've downloaded ngrok.
So what I've got to do is I've got to start a terminal window, or command prompt
if you're on Windows, and I have to get myself in that terminal window.
I have got to go into that downloads folder, and in Macintosh,
it's user downloads, and I do an ls-l, and I can see that this ngrok is here,
and this was the zip file, and I can start it by saying ./ngrok.
It's important that I don't have to run ngrok in the same as where my code's at,
because ngrok is basically forwarding port 8888, four eights, to the web.
So I'm just going to say ./ngrok http, we're going to fake the http protocol, and
local host, the 8888 port on this local host, and if all goes well,
ngrok is going to wake up, and then it's going to tell you an address.
Now the key to this is that this address is only going to work while this ngrok
program is running.
A program is running now and forwarding all these connections.
So the thing to do, and you'll get a different one of these every time, and so,
if I go here, and I go to ngrok.io, You will
see exactly what happens if you go to local host 8888, see?
All that stuff, and my assignments are sitting here in assignments.
I can go to assignments, and I can go into the guest folder, and
now I'm here, except this URL is a real URL.
This is URL that can run anywhere on the Internet.
This URL can only run
on a browser that's running on my computer sitting at my local host.
So now I can use this guess.php and I can turn this
into The autograder,
so I gotta go back and I gotta launch the autograder, and give it this URL.
So now I'm going to say run this, this is a real URL anywhere on the Internet,
including where this autograder is running from,
because this autograder's really running somewhere on the Internet.
So, what happens is, when I hit EVALUATE,
We'll go back there, when I hit EVALUATE this is going to connect to ngrok, and
ngrok is going to send data to your computer, and
the request response cycle's going to come back.
Now, interestingly if you watch you can see this happen here.
As so you've seen I've already done some get requests, and
there's actually a little monitor guy that I can put up over here,
127.0, that's another word to local host, and
this is actually allows me to inspect the data that's going back and forth here.
So my autogrator talks to ngrok, ngrok talks to your computer in a reverse way,
and you're watching this data that's going back and forth, and
that's what's going on here, and here.
Okay, so both of these are talking.
So I'll just leave this, let's make this a little more narrow now so
you can kind of, lets put this maybe way over here, so
you can see it, oops made too small, now it's not looking good, okay.
Okay, we'll watch it over here.
So now I am back where I'm going to do my evaluation.
You can watch action happening over here.
Now one of the things about this assignment, depending on who you are,
it gives you a different number, so that's why you got to change this code.
So I'm supposed to make 37 be my correct answer to get full credit.
So I'm going to evaluate it, and you can see it's talking.
See, it went talking.
Didn't find 'Chuck Severance' in the title tag.
Guess is too high, no.
The key is, you're like what's wrong, look at the toggle, okay?
So, it's like did not find 'Chuck Severance' in the title tag.
Well, that's because of Charles Severance, okay.
Looking for your guess is too high, it says your guess is too low.
You see, it's always trying to tell you as much as it can.
I'm not trying to make this tricky, and so the problem here is this code
that I've got, that's guessed code, we got 42 as the right answer.
So I can fix my program by making 37 be
the right answer, 37, 37 save.
Now I can rerun the text and I should pass that stuff, and these errors went away but
Chuck Severance is still not in the title text, so I change that.
Chuck Severance, and I rerun the test, and I got passed.
Okay, so there we go.
Everything is good.
I don't know what that internal error is.
That's probably because I'm an instructor, yeah, but.
So there you go.
So that's the basic idea of how you run Ngrok, and the way you finish this,
when you're all done with this, is you just hit Ctrl+C.
So remember this, afa30 something.
So I'm going to hit Ctrl+C, and now this URL ceases to work.
All right, this one will blow up, because I'm not there on the other side, so
it doesn't find it.
If I run ngrok again I start the tunnel back up,
but you will notice I will get a different number, 5eb something.
So this address no longer works, but this one does.
So you can start and stop Ngrok as many times as you want, but
you sort of have to realize that every time you start and stop it,
you're going to get a new, you're going to get a new address.
Now, you can actually pay money to them to get permanent addresses, etc., etc, but
as long as you know how to switch back and forth, and get the right address,
it should not be difficult, whatsoever.
Okay, and so there we go.
I hope this has helped you understand how to use ngrok so
that you can send your assignments from your laptop web
server all the way to the autograder on the Internet.
[MUSIC]
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