In a narrower sense, a server is a collection of specialized programs: utilities, heterogeneous services, packages, etc. Some other users and not only they mistakenly call large sites or computers servers, but this is not entirely correct.
The main task of the server is to ensure the correct operation of one or more websites. The client (browser) requests information to obtain data of certain resources, which are indicated by URLs. In response to the request, the server transmits the necessary information via the HTTP protocol to the browser. Thus, the client gets access to the resource of interest. The server is engaged in serving any number of clients, flawlessly performing all their tasks in the order of a virtual queue.
Today, several large servers are known that provide the operation of the entire World Wide Web. These include: IIS from Microsoft, nginx, lighttpd, Google Web Server, Rootage, Cherokee, THTTPD, Resin, and Apache. Moreover, Apache is considered the most widespread server, accounting for more than half of the server market.
There are several types of servers that differ in their functions:
- Database servers play a dominant role in most enterprises, so they receive close attention from manufacturers, sysadmins, engineers and other professionals. Such servers work almost everywhere all the time, without downtime;
- Mail servers are designed to perform all types of operations related to e-mail: sending, receiving, storing letters, etc .;
- File servers serve to centralize the storage of various files and organize access to them. These servers have a powerful disk subsystem that provides basic functions as well as data protection;
- Application servers work with the application server side;
- Web servers are designed for optimal resource allocation among clients on the WAN;
- Backup servers are used to preserve the backed up data;
- Communication servers are divided according to the characteristics of the tasks they perform: firewall - ensures the security of the infrastructure, dhcp servers - dynamically allocate ip-addresses, proxy servers (for example, such proxy-seller) - perform the function of buffering requests, VPN servers - are needed to create private virtual networks.
Purpose of servers
In order to understand what servers are needed for, let's try to imagine the work of at least one enterprise working via the Internet. In this case, the server makes it possible to combine all the resources of the employees of a given enterprise into a single data array that is available to any employee. A kind of multi-user center is being created, which makes it possible to significantly simplify communication between employees, which increases the speed of work and its quality. In addition, in the process of work there are more opportunities for correcting errors, which leads to a decrease in their total number.
Ordinary users use the server to receive and send e-mail, exchange files, communicate on social networks, receive the necessary information - in general, working on the Internet is unthinkable without servers.