Website development by prismintelligentsolutions.com.au

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• Publié par: teamdamien5
• Publié le: 10 février 2014
• Nombre de lectures: 9
• Licence : En savoir +
  Paternité, partage des conditions initiales à l'identique
• Langue: English

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website development by prismintelligentsolutionscomau  websites,google,internet http://www.prismintelligentsolutions.com.au Level 7, 91 Phillip Street, Parramatta NSW 2150 1300 4 PRISM (1300 477 476)  http://www.youtube.com/watch?v=dExKylMe3zE   you go ahead on the internet on yourlaptop or desktop you pull up your favorite browser you type in www.google.com and hit enter What happens? Let's tell this story andwe can be as high level or low level as we want, and I'll steer us in bothdirections. So you've hit enter. What happens? Anything you got? Oh. Good. So that's the whole story. That's very good. Let's tease it apart a little bit now andI'll repeat some of the answers sometimes into the microphone so thatour folks who are taking the course from afar can hear everything so your computer makes a request through your modem goes to your ISP, reaches google.com serversand they've replied with the response, so good. now let's dive in deeper there, and let's focus onthe act of hitting enter Does someone want to propose, just give me one step in more technical detail what happensnext and then we'll get to that same endpoint eventually Perfect. So we first need to translatethe name of the site in this case the www.google.com into an IP address and, someone else,what is an IP address? Good, so an IP address identifiesa server or computer on the internet and an IP address is simply a number ofthis form. Let me go ahead and pull up a little scratch pad for notes here so an IP address as you've probablyseen as something in the form of w.x.y.z and little internet trivia: each of these placeholders can be adigit from what to what? ...or number from what to what? Perfect. 0255, and there'ssome restrictions on what numbers can be where, but essentially you have numberdot number dot number dot number. And each of those numbers can be again 0255. If we've really wanna start pressingdeeper here, how many bits is used to represent an entire IP address underthis schema, for those familiar with bits. 32. So why is that? Well, forthough less familiar/unfamiliar, if you want to represent the number 0  255which is a total of 256 numbers you need 8 bits because 2^8=256,But we won't go into too much detail on along those lines

but if you've seen that IP addressesare just 32 bits it is because each of these numbersis 8 bits itself so actually let's go here. There will be much math in thiscourse after at the following sentence really but if you have 32 bits:how many possible IP addresses are there for the world's computers? so it's to 2^32 which is roughly..those who are good with math in their heads..? So it's roughly 4 billion. So that's a lot.But these days most of you have laptops. Most of you have desktops Most of you have telephones in your pocketsor Ipads or the like. So there's more to placesthese days that are consuming IP adresses so if you follow the popular media of late you'll find that people havebeen freaking out that were about to run out of IP addresses but that'sbecause we've been using version 4 for far too long. Thankfully version 6 (u.v.w.x.y.z) has begunto get rolled out and version 6 (u.v.w.x.y.z) will have128 bit IP address ..which is great, because that's2^128 which is huge! Barely pronounceable. But it will also become alittle more complex to break these things down so we can squeeze a few moreyears of discussion out of these addresses but realize the world is transitioning now just for the sake of the experiencefor those at home let me actually pause here just so we can plug in this recordingdevice so we can capture to another format so let's leave that is thatcliffhanger for just a minute or twoand I'll be right back. Where did we leave off?You've just hit enter.We had proposed that your computer had translated or needed to translatethe hostname www.google.com into an IP address and then we talkedfor a moment about various forms of IP addresses so let's now push a little harder on howthis translation happens so Google has a numeric address of thisform (w.x.y.z) and as an aside Google actually probablyhas a whole bunch of IP addresses of that form. All of which lead to the same experience but perhapsdifferent servers so how does your little Mac or PC orLinux computer know what the IP address of www.google.comactually is? OK, good. So, it has to do a domain namelook up using a DNS server. For those unfamiliar, DNS is domain namesystem and this is an infrastructure on theinternet that pretty much does exactly that. It converts domain names andhost names to IP addresses and vice versa and will see tonight thatit does a few other things in terms of helping with the routing of email with validation of ownership ofdomains and the like so there are these servers out there nowyour computer or your home probably doesn't have its own DNS server but probably Harvard does if you're oncampus or Comcast does or Verizon or your company does.

Now if you're at a small college forinstance and you're not visiting google.com but your visiting some random website.comIt's very possible that you were the first person on a campus to visitthat website ever or at least in a long time so what if your small little campus'sDNS server has no idea what this IP addresses is? Are you sort of out of luck because youwent to that school, and not one where there's more people using that websites or equivalently, it's kind of the chicken and the egg problem (which came first?) if you're the first person to ever need to visit that website andtherefore your campus's DNS server has no idea what that mapping is how do you solve this problem? Exactly. So there's a hierarchy,thankfully to the DNS system whereby even though you might have your ownDNS server on campus or company but that doesn't necessarily store allpossible domain names and IP addresses in the world. In fact, that would be quite alarge database otherwise and it's just not efficient to keep all of them aroundif they're not being accessed at all or very frequently but your ISP knows some bigger fish and maybe thatbigger fish knows an even bigger fish that has its own DNS servers that mightknow, but in the worst case if no one along this hierarchy knows,there also exists in the world what are called root servers which are spread out geographicallyacross the several continents and it's those root servers thatessentially know who does know, what the IP addresses ofsome random website.com in other words those root servers know who the authority is for instance forall of the .com's in the world, for all of the .net's or the like so that you can have this initialrequest from little old your computer bubble up to these very highlevelservers and then bubble back down to some authority who does actually know and the reason why that works is because when you go and buy your owndomain name which is a process will discuss in just a bit you have to tell the world what the IPaddress is of you DNS server, so someone has tobe informed proactively once really and only once when you buy the domain sofor now let's come back to our story We've hit enter Google.com was in my browsers window.My computer has somehow figured out that it is 1.2.3.4 or something like that so now my computer puts together amessage to send it across the internet to Google.com.What does that message look like? Well in it's simplest form  it's a messagethat pretty much looks like this. It is literally the word GET in all capsa space a forward slash ( / ) if you're just requesting the root of the web server markedtypically with / and then HTTP /

version number Now in reality, there is a few more headers,so to speak, HTTP headers that get sent from browser to server, and we'll seethose in action in just a bit, but this message captures really the most important aspect of therequest so your little computer creates avirtual envelope more technically called a packet of some sort inside of thatpacket is a message like this Put on the front of that virtualenvelope is a "To" address namely 1.2.3.4 or whatever Google's IP addresses is. In the return field of this virtualenvelope you know just like you were mailing something to a human there's thereturn address who which should be who's IP address probably? Your own IP addressing, and yourcomputer does know that if you have an internet connection and then your computer sends it out on theinternet. Now we can dive deeper and deeper and deeper but for now assumethat your ISP has what's called the defaultgateway also known as a router and routers are the computers on theinternet that know how to get data from point "A" to point "B", or if they don't know precisely how to go for "A" to "B" they know whom to pass it off to who can then get it one step closer topoint "B" so in reality a packet, this virtualenvelope, might go from router to router to routerto router sometimes as many as thirty different routers across the globe until finally it gets to its actualdestination Google.com. Google receives this virtual envelope, sees that it's for its IP address,opens the envelope up, sees this message Google.com server happens to berunning a web server and so that webserver looks for the file called "/" now "/" is typically a synonym for anactual file name like index.html or index.php or any number of other default standard file names so Google grabs that file from its harddrives and then puts it it's an own virtual envelope flips the two IP addresses the from andthe sender sends it back to the internet via theserouters it arrives on my computer. My computer,unbeknownst to me, opens this envelope sees a whole bunch of a language calledHTML renders that HTML top to bottom and Isee the search page for Google's main site What is the function of the slash? so whenever you type in a URL There are several differentcomponents to it. HTTP typically followed by :// followedby something like this (www.google.com/) and so this is let's say arepresentative URL, but we can actually to tease this apart into a fewcomponents.

This is the protocol or schema at thebeginning, even though in a browser we almostalways used HTTP:// Have folks seen others? HTTPS, similar, but different, inthat it uses cryptography  a topic we'll come back to. FTP://SFTP:// WEBCOW://Some of these are more standardized than others but the schema is typically an indicatorto some piece of software how it should view the contents atthat address so what comes after the ://It typically has something called a hostname or sub domain name followed by the domain name, which inthis case is google.com or followed more precisely by a domainname witha TLD  toplevel domain a .com .edu .gov .uk would be the TLD and then you havewhat we call a path and a path specifies exactly what fileor folder you wanna access A single slash means get me the root ofmy hard drive and if you come from the windows worldthis is essentially equivalent to C:\ Or on a mac it's equivalent tothat, or on a Linux computer it's equivalent to that. So that is truly the root of your harddrive, the folder in which everything else onyour hard drive lives now it turns out in a browser thesedays you don't have the type most of that. you can omit the HTTP://You can typically omit the www.You can omit the slash, and things just work Why is that? both for the most part it'sbecause browsers have just gotten a lot more user friendly right there what was the time a fewyears ago where advertisements in print and on TV would actually haveHTTP:// but then the world kind of realized thatyou know anytime you see www. something probably a website so we startedomitting HTTP:// Now the world has gotten acclimated toany mention of .com or .gov so we don't even really need the wwwanymore and so whether or not www works or doesn't work is actually completely configurable bythe system administrators of the website and in fact i don't have a sort of a soapbox to hop on right nowbut invariably during a semester, I'll come across some website for which foo.com or whatever thedomain is .com just doesn't work you have to type inwww.something.com and that's just a foolish technicaldesign decision on their part. We'll talk today about how you can configure thingsto just work, and it involves a bit of DNS a bit of web server configuration but typically you don't see that dead end because browsers these days if you typein foo.com and hit enter and there is no foo.com IP address out there

the browser will presumptuously or helpfully prepned "www." to the start of theaddress and then retry that one some browsers if you just type foowill automatically try foo.com, foo.net, foo.gov some of the most popular ones so inshort a lot of the technical processes thatare happening are being sort of hidden now by browser user friendliness for better or for worse

So, the story began with hitting enterthe story ended with you're seeing the home page of Google.

Any questions on the various steps inbetween, whether high level or lower level? Allright, so that's the story told from theperspective of a user. Why don't we tell the story from theperspective now of someone who owns a website or wants to operate a website sosuppose one of your goals in this class or some other

is to actually have your own presence onthe web to actually buy your own domainname and have your own business or personal home page or whatever the casemay be.

How do you go about doing that? You needmore than just a laptop and a browser now you need a server on the internet because even thoughevery computer on the internet, your laptop included has an IP address it's not necessarily publicly accessiblebecause even that statement's a bit of an oversimplification. You do not necessarily have apublic IP address. In fact if you go home and you have internet access at home,especially wireless you probably have a home router like anApple Airport Extreme, or you have a Linksys router or some device with antennasthat gives you wireless internet access but Comcast or Verizon or whoeveryou're paying each month to give you internet access into the house via yourcable modem or DSL modem which in turn is probably connected tothat router if it's not one in the same device whichsome of the ISPs provide these allinone devices these days Odds are you have one IP address and if youhave 3 brothers and sisters or parents or grandkids in the house all of you are sharing that one IP address and yet the individual computers in thehome still need an IP address. so what actually is the case is thatwhen you're in a home network you have what's called generally a privateIP address something of a form.. Anyone know what up popular internal IPaddresses is? Exactly. Anything, in fact, starting with192.168.x.y is a private IP address, so the folkswho invented the internet along the way decided "You know what? Weshould probably have some IP addresses that should never be given out." So that within the company or home or alittle test network you can have IP addresses that areguaranteed not to exist on the public

internet so what home routers typically use iss192.168.0 or 192.168.1 and then the last digit, it can be againbetween 0255, but some exceptions. It really it can't be 0 or 255, so there are some constraints, but it gives you roughly 250 or so possible IP addresses If you don't like that, there's:172.16.x.y There's a few more constraintson this one, but then if you really need a lot of internal IP addresses you can have what's called a "class a"private network 10.x.y.z is a private addressand this actually gives you millions of IP addresses for your home or yourbusiness or your data center, but in short any IP addresses beginning with thesefew other prefixes are considered private

but the problem then is that even ifafter this class you know HTML and CSS all the better. You know PHP, and SQL, and Javascript and you creates a website and you'verun it on your laptop using software we'll introduce you to.A web server called Apache no one in the world is going to be able to visit yourwebsite because your address probably starts with one ofthese prefixes and your home router or cablemodem or DSL modems is not going to let outside random people into your homenetwork to access this IP address because frankly there's tens of thousands ofpeople who probably have that exact same private IP address, so it's justuniquely identifiable and because your home router and your cable modem is sometimes afirewall into itself this traffic not gonna get into your home so in short that won't work.. but you have at least two options, twoalternatives, how can you get your website out on the internet? You can. Port forwarding. So let's gothere. For those unfamiliar when you use a protocol like HTTP:// you're actuallyusing other protocols behind the scenes and in fact you probably at leastheard the the buzzword TCP/IP transmissioncontrol protocol internet protocol It's actually two protocols, two differentstandards or languages so to speak that govern how data can be transmitted on the internet and this is a bit of anoversimplification but for today's purposes assume that IP, the internet protocol, is just a set of conventions thathumans came up with years ago that govern how you associate numericaddresses with computers so IP address derives from thisprotocol so IP is just the standard for assigning computers addresses however justsigning someone an address doesn't mean you can get data to thataddress for that you need another standard another protocol and that's typically TCP transmissioncontrol protocol

So TCP is the standard that web browsers and web servers speak in order to actually physically move dataor electronically move data from point "A" to point "B" using the higher level notion of anIP address to actually uniquely identify points "A" and point "B" so for those who might want to go further in computerscience and in networking in particular there's typically what's called theTCP/IP stack and so there's topics like there's thetransport layer down here there's the others the IP or addressing layer here there's the application layer in shortmuch of the internet is the result of smart people having design things andthen design things on top of things on top of things and so we just typically over simplifyand say TCP/IP. So what's the point there? TCP/IP allows not just the web towork but all sorts of applications There's the web. There's email. There's instant messaging. There's things like Spotify. There's dedicated applications they're using the internet but aren't necessarily inside of abrowser so a server can actually do multiple things.It can receive email like Gmail can. It can be a website and get HTTP:// traffic so a server because it can do multiplething somehow needs to be able to uniquely identify the various things that it can do and so the world introduced this notionof port numbers and typically for a web server Rather, for HTTP:// it uses thisprotocol TCP and the world decided some years ago the number 80 will arbitrarilybut consistently identified this service so if you have a server and you have awebsite, and a website uses, as you probably know, HTTP:// but will look atwhat that means in a bit it is running so to speak on port 80it is listening so to speak on port 80 and the motivation for that is because you might also have an email server on the same physicalbox , right? Gmail, kind of an oversimplification, but they are both awebsite and an email service, and if you want to be able to send email to Gmailyou can also used TCP but you have to use port 25 in other words if you've go to http://www.gmail.com a with a browser you obviously want toweb page back so even though you, the human,haven't typed 80, it's automatically inserted for you by your browser, behindthe scenes but if you send an email from Eudoraor apple mail or Outlook or whatever you're using you again probably don't have to care aboutthis detail but that program

is going to send data still to gmail.com but specifically to port 25. So, when a computer's on the internet, aserver, and it's listening for traffic all of that traffic comes in on a specificport a specific like pathway into the server so that it knows if it's a webpage or an email, right? Because especially email; emails can contain HTML now so you need some way of distinguishingthe two fundamentally so when you propose port forwarding, whatdoes this mean? Well, if your home network has a public IP address, and you usually, again, get 1 from your ISP and that is some address of the formw.x.y.z and your individual laptop on whichyou've created your final project that you wanna make publicly available is that one of these IP addresses,doesn't really matter what it is, what you can do is configure your homerouter AKA firewall AKA cable modem, it depends on what make and modelyou have, but that device, you can configure it to say anyinternettraffic that comes from theinternet to my home on my public IP address destined for port 80 should be "port forwarded" to IP address 192.168.x.y port 80 in other words you can tell this machineto take incoming data on that port and then route it very specifically to thiscomputer, your's, so that it just works. Now, there is one gotcha here. Especially if you have siblings, for instance orother technically minded family members or roommates if you're doing port forwarding in thisway only one of you can operate a webserver behind your cable modem because you onlyhave one IP address to uniquely identify your website and if you'vealready claimed 80 as your own and that's the default for the worldbrowsers to use pretty much only your webserver can be accessed now there is a work around here if yourroommates really ticked off at you, you can say "Fine, fine, fine, I will give you port 81." but what does that mean? That means theentire world has to type out a URL like let's say your address was indeed w.x.y.z this would be your IP address your URL your roommates, unfortunately, would be thiscrazy looking thing (http://w.x.y.z:81/), right, or any number really. Now, there are some restrictions on thenumbers. Probably can't use 81, but the point is the same. This is not standard, and you probably don't want your users having to remember such an esoteric detail as an arbitrary number. However if on the internet

you visit any website with :80, odds are you will get to the websitewith which you're familiar it's just the browser is again for user convenienceinserting the port number automatically for you.

and little trivia for HTTPS, the secure version of HTTP, what port number does that use? 443, and you sometimes do seethat in the URL and you also see some other ports commonly like :8080 :8080 is just kind of arbitrarypopular port that some companies used to run certain services but in short usinganything nonstandard these days especially for commercial production websites where you're trying to make money or trying to stay online up one hundredpercent of the time using non standard ports is bad, because thereare certain companies, there are certain campuses that will pretty much block anyports besides 80 and 443, but thankfully there's a work around,even if you wanna run some random server like a bit torrent server, or something likethat all you have to do is change the portnumber to be 80 or 443 so the reality is that with firewalling and willhave this conversation toward the end the semester, when we talk about securitymore generally,

in a lot of security mechanisms are kindof a joke because all you need is a modicum of savy or you know, having listened to the past30 seconds of words that I just said you can circumvent these kinds of restrictions. Hotels do this a lot,Starbucks does this a lot the port numbers are really just this verybasic mechanism, and the world and adopted somestandards, alright, so, perfect! We have a solution. All youhave to do is somehow figure out how to download the manual for yourLinksys router or Apple Airport and you can configure all this portforwarding stuff and run a website from your own, so not quite. Because if you actuallyhave a popular website, Verizon and Comcast might very well notice and just shut you off entirely, because that huge disclosure agreementyou probably clicked through and never read when you signed up for internet serviceprobably said you may not run a website on your home computer so plus that this was a pain in theneck to do anyway, plus I might unplug my laptop sometimes and so mywebsites gonna go down anytime i go to go out so not the best solution even if youhave a desktop so let's at least try to push a little harder and assume that weneed to outsource this problem, or we at least need to put your computer on the internet itself, in a data center,on the campus, where it can stay plugged in perpetually, under your desk at work ifthe system admins allows it, and moreover i don't want my website to live atw.x.y.z, or any number for that matter, I want it to live it david.com orsome URL that is sort of distinctly my brand ormy name, so that begs the question how do you goabout getting your own domain name? Has anyone done this before? Yeah, how do you do it?

Okay, where do you purchase them? Okay, so namecheap.com is a verypopular place, fairly inexpensive Go Daddy is another very popular place This one (Go Daddy) is kind of riddledwith upsell attempts, trying to get you to buyeverything in the kitchen sink, but you don't need to do that. There's all there's all sorts of domain name registrars out there thesedays. A bunch of years ago network solutions was the only one, but then the market was created and sothere's a lot of places to buy domain

names. For the most part, it doesn't matterwhere you buy your domain name from, but you do sometimes get different features in particular you get DNS featuressometimes, more control over your DNS

servers. They might throw in free email accounts,free hosting, but for the most part, it doesn't matter a hugeamount in particular, you don't need to go to someone like network solutions andpay thirty dollars a year, when you could go to someone like Go Daddy and pay$9.99 a year or namecheap and pay $4.99 a year so in short paying more for domain name isn't necessarily giving you anythingmore uh... in the way of

uh... functionality. It depends on what maybe the addons are. So, how do we go about doing this? Well,let's go to something like Go Daddy. Go Daddy's kind of a...Well, let's actually try namecheap. Let's go to namecheap, see what theylook like, much of my friends have indeed used thiswebsite. right so let's see domain name to searchand the search for david.com probably take. Oh,l that is a goodprice. Already doing better than Go Daddy All right. So as I expected it is takenas are almost all forms of david. *Ha* They've suggested I name myself "DavidJohn", "David Smith", "David Johnson", "King David", "David Photography.us" So one of the hardest things, frankly, ofstarting a business these days is finding an available domain name, let aloneyour own personal vanity domain names for people's names but if we found something we like.. MaybeI do want DavidTV... Well, that's atrocious. $6,000 for this domain but it's not yet taken. It's probably one of the cheaper onesup above so let's assume we found something we're happy with so we add it to our cart and we check out I now own some domain name,David something.com. So what now do I do with it? How do I associate it with my web server? and for that matter, how do I get a web server?Let's assume I have a web server, and we'll cross that bridge in a moment, but I have a domain name. What do I need to do with it to startusing it? Well I need to tell the world what my IP address is.

So I need to, somehow, tell the world thatmy server.. I don't know who's going to be hosting it, but i know it will have aIP address, by nature of how the web works.