What is a server?
A server is a system designed to provide access to resources, services, data or software to other computers, which are called clients, through a network.
In general, servers are computers that share resources with “client” computers, but in addition to providing resources they can also use those of other systems.
1. How does a server work?
The servers, whether physical or installed in virtual machines, are programmed to be always active and respond quickly to requests from clients or other servers. For this reason, they are never turned off and the term availability is used to indicate the time that the server is active and ready to respond to requests.
For example, an email server has all the features that allow it to listen and respond to requests from clients/servers, in terms of receiving and sending emails. Working on other additional operations at the same time, such as spam detection, consulting blacklist services, checking the sender’s DNS, etc.
2. Types of servers
There are very different types of servers depending on the tasks for which they have been designed, but in general, the most common is that we find the following types:
- File servers. These servers are used to share and store files, so that other servers or clients can access them easily, they generally have permission levels and access restricted to unregistered users.
- Application servers. These servers are the ones that allow you to run (use) applications remotely without the need for the client computer to have the application installed locally. That means the software will be installed in just one computer.
- Database servers. They are used for managing huge amounts of information through the use of databases that generally require a very large amount of storage space and respond to queries/requests for information from customers. The most common database servers are Oracle, Microsoft SQL Server, and DB2.
- Email servers. They are one of the most common application servers and are used for managing sent and received emails in the clients’ email managers. To send emails, it is possible to use SMTP servers. For receiving messages, there are pop and imap servers.
- DNS servers. These are the domain name system (DNS) servers that are responsible for redirecting to an IP address, based on a domain name written by the user. Print servers. It is the one that manages and administers the printing and distribution of documents among the different clients. High-end printers have their own built-in print server.
- Proxy servers. They are the ones that act as an intermediary between a client and a server; they are often used for isolating clients or servers from others, for security reasons.
- Web servers. After email servers, they are the most used ones. They are a type of application server that stores the data and applications that are requested by browsers so that users can view web pages. The most common web servers are Apache and IIS (Microsoft Internet Information Services).