#clientserver

Client-Server là mô hình mạng trong đó máy khách (Client) gửi yêu cầu và máy chủ (Server) xử lý, phản hồi. Đây là nền tảng của hầu hết các ứng dụng web, email và hệ thống doanh nghiệp hiện nay nhờ tính tập trung và khả năng mở rộng.

Đọc chi tiết: Client-Server

4 essential characteristics of successful APIs - For any external system/app to connect to a server system

 If you are building an application that uses some variation of a client/server model, you need an application programming interface (API). An API is a clearly defined boundary between one process and another. A common boundary in web applications is a REST/JSON API.

 An example of an API usage could be a police system that must verify if someone has a criminal record or not, for applying maybe for a liquor license business. Where paperwork was sent manually to the police to verify whether the liquor license applicant has a criminal record or not, could be replaced with an intersystem API call from the liquor licensing system, where the API receives an identity number, and only returns and true/false without exposing any personal details.

 But some important characteristics must be designed into that API for it to be sure and to function correctly.

 See https://opensource.com/article/21/5/successful-apis

 #technology #API #programming #privacy #clientserver

Anyone can learn basic Web development skills, even with very little technology experience. Whether you're hoping to simply manage your own website or want to create sites for other people, you first need to understand a few basic concepts which we will run through in this tutorial. In the next part we will explore website building, including basic HTML.

Domains

One of the first steps in creating any website is choosing a domain name. The domain name for a site acts as is its address on the Web. As you may know, visitors use the domain name to access the content of a site. However, the underlying implementation of Web addressing is a little more complex. Website content is stored on Web server computers. Computers are assigned IP (Internet Protocol) addresses in order to connect to the Internet. This includes Web servers hosting the content of websites and the computers accessing that content through Internet connections, for example your own PC, smartphone or other device. In reality, your IP address may change each time you connect to the Internet - this is managed by your ISP (Internet Service Provider). An IP address is a string of numbers. Since it would not be feasible for users to type the correct IP address into the browser whenever they want to access a site, the Domain Name System (DNS) translates between the IP address and a more human-readable string of characters - the domain name. When you type a Web address into the browser, a name server looks the domain up in a database and connects you to the site at the relevant IP address. Domain Name Syntax As you may have noticed, a Web address is made up of a few sections separated by dots and slashes. Look at the following example: http://www.w3.org As you will know from browsing the Web, you don't normally need to add the "http://" part (the protocol) in order to visit a site, however, you will need to include it when you build HTML links later. In most cases you can also ignore the "www" when visiting websites, since the communication between your Web browser and the name server will resolve the domain you entered to a relevant IP address. The main part of the address that you need to consider when setting up a new website is the "w3.org" section in the above example - this is the domain name. The ".org" part of the domain name is referred to as the top-level domain name. Every domain within each top-level extension (".com", ".net" and so on) must be unique. This ensures that when anyone types a domain name into their browser, they will be connected to the correct site. When you choose a domain name for a new site, you therefore need to find one that is not already in use. To use a domain name, you must register it through a domain registrar. You can register a domain name directly with a registrar yourself or can do it through your Web host. Before we move on, take a look at another address: http://validator.w3.org/ This address includes a subdomain: "validator". When you create a new website and choose a domain name for it, you will have the option to use subdomains to organize the parts of your site into logical sections. You can also include sub-directories within a site - you can structure Web addresses to link directly to the files and folders within your website as you will see in the next tutorial.

Web Hosting

To create and manage a website, you need to purchase a Web hosting package. (There are free ways to create a site, but they don't afford you full control over its content.) When shopping for a hosting package, you will see that there are lots of options in terms of the services you can have. If you just plan on hosting a single site, or are looking for a basic service to start learning Web development, you can choose a starter package. If you plan on creating multiple sites for other people as a commercial service, you may need a reseller package. With the advent of Cloud Hosting that enables you to utilize the power of a cluster of virtual server resources, you can find economies of scale i.e. you can host multiple sites within the same account making it easy to manage. Also scaling on cloud is pretty easy ensuring that you do-not overspend on underutilized capacities. Before choosing a host, it's well worth comparing the available options and of course reading any reviews you can find. There are a few basic features to check for in any prospective package you consider. Storage space and bandwidth: Your Web host will provide set amounts of storage space for the content of your site and bandwidth to accommodate the data transfer that occurs when users view it. Support: If your site encounters problems you may need technical support, which varies from host to host but is often available through email, telephone and live chat facilities on the host website. Payment options: You may be able to pay for your hosting on a monthly or yearly basis. Domain registration: Many Web hosts provide domain name registration as part of their hosting packages, including the ability to use subdomains and email addresses in association with a domain. Technologies: Although you may not need it at first, your host may offer support for particular scripting languages as well as the ability to manage databases for your site. Most of the vendors now offer several CMSs, frameworks out of the box or a "single click to deploy" options making the services very non tech user friendly. So you need to ensure the hosting provider is optimized for the technology you are looking to use; for .e.g. Bluehost is optimized for WordPress and is an ideal fit for Websites based on WordPress Site management tools: Other tools you may benefit from include control panels and Content Management Systems for administering the content of your site. If you choose a Web hosting package and later decide you have additional needs, you can generally upgrade without too much hassle.

Web Browsing

Before you start the process of creating your first Web pages, it's vital to understand exactly what happens when someone visits a website. The user visits a Web page either by typing an address into their browser or by clicking a link in another page, including search engine results pages. The Web browser (Firefox, Chrome, Internet Explorer, Safari etc) sends a request for the page. The server responds to the request, normally returning the content of the page, which is then displayed in the browser. When the server hosting a site receives a request for a page, a number of things may happen. The simplest case is where the content of the Web page is saved on the server in a file with ".html" extension. In this case the server simply returns the content of the page to the browser. The browser is able to process the HTML structures in the file in a way that renders the content (text, images, media and so on) to the user in a readable way. The content saved in a file stored on the server in this way is referred to as static. In this scenario, the content served to the user's browser will remain the same until someone edits the file and uploads it to the server again. In the past, Web pages tended to be static, but with the advent of new Web technologies, alternative ways of serving content to website visitors emerged. In contrast with a static page, a dynamic page is built when the user requests it. These pages typically use server-side scripting in programming languages such as PHP. When a user requests a dynamic page, a script on the server runs, writing out the content of the page and returning it to the user's browser. The content received by the browser (the client) is typically still structured in HTML markup code, so from the client point of view nothing is different. The difference between static and dynamic websites relates to what happens on the server. When a server-side script runs, it can fetch data from a source such as a database, writing the retrieved data into a Web page. This means that a dynamic page can potentially be different each time someone browses to it. Many automated Web authoring tools such as Content Management Systems also use server-side scripting.

Next Steps

Client-Server Computing and Its Benefits

[ad_1] There is little disagreement that the implementation of client/server computing can result in current and future savings, but this new technology usually cannot be justified on cost/benefit analysis alone. The other major benefits are intangible and hard to quantify. Dollar Savings: Mainframe environments are costly to maintain – the hardware, software, and staff required to maintain and…