1 00:00:00,210 --> 00:00:00,700 Beautiful. 2 00:00:01,020 --> 00:00:07,740 And once we have a general understanding how data is exchanged on the Web, let's also cover how HTP 3 00:00:07,740 --> 00:00:09,750 messages are structured. 4 00:00:10,170 --> 00:00:16,410 Please keep in mind that since it's going to be a big part of our job, we'll come back to this particular 5 00:00:16,410 --> 00:00:18,050 slide more than once. 6 00:00:18,480 --> 00:00:24,900 So if you hear about something, just please be patient and I'll answer all of your questions as we 7 00:00:24,900 --> 00:00:26,170 move along with the course. 8 00:00:26,550 --> 00:00:31,300 With that said, the general structure for both messages is similar. 9 00:00:31,710 --> 00:00:33,390 They both have a startling. 10 00:00:34,260 --> 00:00:41,970 They both have optional headers, a blank line that indicates that all the info has been sent and effectively 11 00:00:41,970 --> 00:00:46,650 headers are that info as well as optional body. 12 00:00:47,010 --> 00:00:49,970 And before we continue again, let me stress something. 13 00:00:50,340 --> 00:00:56,250 So request messages are what the user is sending. 14 00:00:56,670 --> 00:01:03,420 For example, if you open up the browser to search the web, or that could be your Web application. 15 00:01:03,600 --> 00:01:09,660 The remember, with Web applications, we also can make HTP request correct. 16 00:01:10,020 --> 00:01:14,090 And that response is going to be our responsibility. 17 00:01:14,550 --> 00:01:20,820 So we'll have to set up a proper server that sends a correct response. 18 00:01:21,630 --> 00:01:28,770 And in general, when we talk about the request message in start line, there's going to be a method 19 00:01:29,310 --> 00:01:33,270 then the URL as well as the HTP version. 20 00:01:33,660 --> 00:01:40,470 Now, we are mostly going to be interested in these two things in the method as well as the URL. 21 00:01:40,860 --> 00:01:47,640 Now there's going to be a separate slide about the methods as well, and the warranty will cover that 22 00:01:47,820 --> 00:01:52,750 in greater detail once we cover them with actual code examples. 23 00:01:52,780 --> 00:01:54,720 So I'll come back to that slide. 24 00:01:54,720 --> 00:02:00,060 Just understand the general idea that why don't we talk about methods effectively. 25 00:02:00,060 --> 00:02:02,580 We're communicating what we would want to do. 26 00:02:03,180 --> 00:02:09,340 For example, if I want to get the resource, I'm going to set it up as a get request. 27 00:02:09,750 --> 00:02:14,010 Now, if I want to add the resource, then of course this is going to be a post request. 28 00:02:14,370 --> 00:02:16,960 And then, of course, you can read the rest. 29 00:02:17,340 --> 00:02:24,840 Now, while I'm displaying here this get because that is the default request that the browser performs. 30 00:02:25,270 --> 00:02:29,150 Since when we open up the browser, we want to get some kind of research. 31 00:02:29,670 --> 00:02:30,120 Correct. 32 00:02:30,390 --> 00:02:33,030 That's why we're performing a good request. 33 00:02:33,300 --> 00:02:36,360 And the URL is just the address. 34 00:02:36,780 --> 00:02:43,150 And that could be, for example, John Smil dot com or that could be, I don't know, ESPN sports like 35 00:02:43,410 --> 00:02:44,180 basketball. 36 00:02:44,310 --> 00:02:47,130 Both of them are just a Web addresses. 37 00:02:47,430 --> 00:02:55,100 Now, ours is essentially optional where this is a matter of information about our request. 38 00:02:55,440 --> 00:03:00,320 And just to give you a general idea how the headers would look like they would look something like this. 39 00:03:00,420 --> 00:03:02,690 So it is a key value pairs. 40 00:03:03,030 --> 00:03:04,470 Now, don't freak out. 41 00:03:04,890 --> 00:03:09,060 As you know, when you search the web, you don't need to add the manually. 42 00:03:09,300 --> 00:03:12,260 And the same is going to be with our server. 43 00:03:12,600 --> 00:03:15,030 A lot of it is going to be taken care of. 44 00:03:15,030 --> 00:03:18,880 But yes, some things will have to add on our own. 45 00:03:19,240 --> 00:03:27,240 Basically, this is going to be information about our message and then we also have optional body. 46 00:03:27,660 --> 00:03:33,510 So when the user is requesting something, if you just want the resource, there is no body. 47 00:03:33,930 --> 00:03:35,430 There's nothing basically. 48 00:03:35,430 --> 00:03:40,650 What however, if we would want to add a resource onto the server. 49 00:03:40,650 --> 00:03:41,160 Yes. 50 00:03:41,430 --> 00:03:44,580 Then you are expected to provide that there. 51 00:03:44,670 --> 00:03:46,920 And it's also called payload. 52 00:03:47,130 --> 00:03:50,330 So again, I might use them interchangeably. 53 00:03:50,400 --> 00:03:53,460 So that's the general structure of the request message. 54 00:03:53,940 --> 00:03:55,020 We have to start line. 55 00:03:55,020 --> 00:03:56,130 We have the headers. 56 00:03:56,490 --> 00:04:03,150 That is the information about our message as well as the black line, which just indicates that we're 57 00:04:03,150 --> 00:04:08,430 done with the information and optional body, which we'll use from time to time. 58 00:04:08,820 --> 00:04:12,720 And of course, we need to talk about the response message. 59 00:04:13,020 --> 00:04:16,529 So our response message is what we are going to be creating. 60 00:04:16,560 --> 00:04:23,520 Again, most of it will be done for us, but some parts, yes, we'll have to do it manually and it's 61 00:04:23,520 --> 00:04:24,870 going to be our responsibility. 62 00:04:25,230 --> 00:04:30,540 So the START line has the DP version, which most likely is going to be one point one. 63 00:04:30,840 --> 00:04:34,870 Then we have a status code and status text. 64 00:04:35,310 --> 00:04:43,320 Now, when it comes to status code, it just signals what is the result of the request. 65 00:04:43,330 --> 00:04:49,230 So, for example, notice here this two hundred, that means that request was successful. 66 00:04:49,410 --> 00:04:51,000 So that's what we're sending back. 67 00:04:51,330 --> 00:04:54,180 And yes, there's quite a few of those codes. 68 00:04:54,450 --> 00:04:58,590 And as we move along with a course, of course we will cover them. 69 00:04:58,590 --> 00:05:05,610 But please, please, please don't rush over to the search engine and start memorizing the status codes 70 00:05:05,910 --> 00:05:08,310 pretty much as we're going to be building the application. 71 00:05:08,670 --> 00:05:12,420 I'll tell you which code means what, for example. 72 00:05:12,420 --> 00:05:16,830 Four hundred means that there was some kind of request error. 73 00:05:17,250 --> 00:05:21,480 So the user was trying to request some kind of research. 74 00:05:22,290 --> 00:05:25,320 And with four hundred, there was a request. 75 00:05:25,590 --> 00:05:30,690 Now, for example, the code four or four means that the resource is not fun. 76 00:05:30,930 --> 00:05:33,320 So when I'm sending back the message, I'm like. 77 00:05:33,620 --> 00:05:39,500 Hey, listen, here's the status code for the message, if you are successful, here's two hundred. 78 00:05:39,740 --> 00:05:43,340 If there was an error, for example, you get a four hundred. 79 00:05:43,550 --> 00:05:50,180 If the request is unauthorized, then you can get four on one and hopefully you get the gist. 80 00:05:50,180 --> 00:05:55,600 And yes, of course, as we're progressing, we will cover more status code. 81 00:05:55,890 --> 00:06:04,990 Then again, we have the headers where basically we provide info about our message, our response message. 82 00:06:05,510 --> 00:06:10,640 And again, like I said, you won't have to type everything line by line. 83 00:06:10,850 --> 00:06:15,320 But effectively, it is a set up of key value pairs. 84 00:06:15,650 --> 00:06:18,380 And the ones that I would like to mention are these ones. 85 00:06:18,390 --> 00:06:19,610 Notice this content type. 86 00:06:19,610 --> 00:06:21,700 We have text HDMI. 87 00:06:22,040 --> 00:06:25,220 That is when we're sending back the HDMI. 88 00:06:25,460 --> 00:06:30,440 But also our second option is going to be sending back the data. 89 00:06:31,010 --> 00:06:36,110 So hopefully you are aware that when you're building a Web application, when we communicate with API, 90 00:06:36,290 --> 00:06:43,550 most of the time we're getting back the JSON data because over the web, effectively we just send over 91 00:06:43,550 --> 00:06:44,050 the string. 92 00:06:44,510 --> 00:06:50,780 So if, for example, I have some kind of array, we transfer this into application duration. 93 00:06:51,020 --> 00:06:58,220 And I clearly indicate that in my headers when I say that, no, I'm not sending text and email, I'm 94 00:06:58,220 --> 00:07:00,890 actually sending a application, Jason. 95 00:07:01,220 --> 00:07:05,150 And then that application, who is requesting the Web application, knows that. 96 00:07:05,150 --> 00:07:09,970 Hey, from the server, I'm getting a check on the type, which is application JSON. 97 00:07:09,980 --> 00:07:17,030 So, for example, in that case, I could send back here this array with a bunch of these objects. 98 00:07:17,390 --> 00:07:25,400 And just to give you a real world test, why don't we do this, open up a new browser tab and I'm simply 99 00:07:25,400 --> 00:07:28,850 going to call the API because I think there's going to be less data. 100 00:07:28,850 --> 00:07:30,670 So there's going to be less clutter. 101 00:07:30,950 --> 00:07:37,850 So go to course, the API here and then you can either pick the slides or you can just look at the home 102 00:07:37,850 --> 00:07:38,180 page. 103 00:07:38,450 --> 00:07:46,790 And if you inspect and if you look in the browser tabs, you'll find a network and very useful one is 104 00:07:46,790 --> 00:07:51,900 this one where we can just look for all the requests we refresh and then check it out. 105 00:07:52,310 --> 00:07:58,280 So these are the requests that browser perform and I'll talk about it a bit later. 106 00:07:58,460 --> 00:08:03,140 Why there is also this style says, in fact, that's going to be one of our first examples. 107 00:08:03,440 --> 00:08:04,640 But take a look at this one. 108 00:08:04,970 --> 00:08:11,720 So I have this course API and then course and if you remember when we were building our original server, 109 00:08:12,020 --> 00:08:16,000 what I said that if we have this forward, that just means homepage. 110 00:08:16,370 --> 00:08:24,470 So if we're just navigating the course API dot com and that is our homepage, we simply add this forward. 111 00:08:24,770 --> 00:08:27,020 Now, of course, in the browser, that automatically added. 112 00:08:27,020 --> 00:08:33,080 But that's why when we're setting up the server, one of the cases is going to be if the user navigates 113 00:08:33,080 --> 00:08:35,679 to the homepage, then we simply look for. 114 00:08:36,679 --> 00:08:44,090 So if, for example, you go to the slides, you'll notice that in this case I would have to refresh 115 00:08:44,390 --> 00:08:48,740 notice here I have the course API slash slides. 116 00:08:49,070 --> 00:08:54,440 So that is already a page in my website. 117 00:08:54,440 --> 00:08:54,860 Correct. 118 00:08:54,870 --> 00:09:00,770 So I have the homepage, of course, API, and then I have the slides page where I have the slides. 119 00:09:01,100 --> 00:09:08,330 And if you take a look, if you click on it, notice all the useful data that we get over here. 120 00:09:08,630 --> 00:09:11,870 So for example, this is going to be our request. 121 00:09:11,870 --> 00:09:14,630 You are just going to be an API dot com. 122 00:09:14,810 --> 00:09:19,790 So that tells me well what the browser is trying to get, then check it out. 123 00:09:19,790 --> 00:09:23,620 The method wides get because that is default in the browser. 124 00:09:23,660 --> 00:09:27,890 Every time you open up the browser and search something, then of course you'll be performing a get 125 00:09:27,890 --> 00:09:28,280 request. 126 00:09:28,550 --> 00:09:29,260 Now check it out. 127 00:09:29,270 --> 00:09:32,150 This one, the status code, it is two hundred. 128 00:09:32,270 --> 00:09:32,660 Why? 129 00:09:32,660 --> 00:09:38,810 Because everything is successful because server send back the data, then we have this remote address 130 00:09:38,810 --> 00:09:45,050 and basically that is the IP address for my server as well as notice this call on four three. 131 00:09:45,560 --> 00:09:51,170 And we'll come back to this one when we set up our own server, because if you remember, we were always 132 00:09:51,170 --> 00:09:52,460 setting up the five thousand. 133 00:09:52,580 --> 00:09:55,100 So probably wondering, well, what is this for for three? 134 00:09:55,370 --> 00:10:01,130 And don't worry, then we'll cover that one once we set up our first server. 135 00:10:01,550 --> 00:10:07,970 And then again, we have response headers, for example, and we also have the request letters. 136 00:10:08,300 --> 00:10:13,950 So as you can see, using this network type, we can actually find a bunch of useful information. 137 00:10:14,240 --> 00:10:22,700 Now, notice here in the second set of tabs, I can see this response and preview. 138 00:10:23,000 --> 00:10:27,380 So if you take a look at the preview, this is going to be basically my site. 139 00:10:27,620 --> 00:10:29,900 And also I can see the response. 140 00:10:30,230 --> 00:10:33,080 So, as you can see, pretty much sending back the. 141 00:10:34,310 --> 00:10:41,570 So I'm sending back the website, so you go on to the browser, you request resource by default, it 142 00:10:41,570 --> 00:10:46,440 is a request and not in that body when the server sends it back. 143 00:10:46,760 --> 00:10:48,260 This is what we get back. 144 00:10:48,680 --> 00:10:50,580 So we get back to the site. 145 00:10:50,810 --> 00:10:57,870 So hopefully this gives you a clear understanding of how the HTP messages are structured. 146 00:10:58,250 --> 00:11:01,940 And now let's dive into creating our own server.