What is a server ? What does a server do ? How many type of servers are there ?

What does a server do?

A server is a computer that serves information to other computers. These computers, called clients, can connect to a server through either a local area network (LAN) or a wide area network (WAN), such as the Internet.

There are a number of different types of servers, including Web servers, mail servers, and file servers. A web server serves Web pages to computers that connect to it. It also can parse scripting languages such as PHP, ASP, and JSP. 

A mail server stores users' e-mail accounts and sends and receives e-mail messages. For example, when you send an e-mail to a friend, the message is sent by a mail server, using the SMTP protocol. 

A file server is a computer that stores files that can be accessed by other computers. File servers are often used within local networks and typically require a password or some kind of authentication to connect to it.

These are a few examples of some common servers, but several other types of servers exist. Just about any computer can be used as a server if the necessary server software is installed on it. While servers typically don't need a lot of processing power, lots of RAM and fast hard drives are helpful for dealing with heavy traffic to and from the server.

A server is a system (software and suitable computer hardware) that responds to requests across a computer network to provide, or help to provide, a network service. Servers can be run on a dedicated computer, which is also often referred to as "the server", but many networked computers are capable of hosting servers. In many cases, a computer can provide several services and have several servers running.

Servers operate within a client-server architecture. Servers are computer programs running to serve the requests of other programs, the clients. Thus, the server performs some tasks on behalf of clients. The clients typically connect to the server through the network but may run on the same computer. In the context of Internet Protocol (IP) networking, a server is a program that operates as a socket listener.

Servers often provide essential services across a network, either to private users inside a large organization or to public users via the Internet. Typical computing servers are database server, file server, mail server, print server, web server, gaming server, and application server.

A server is a computer that provides data to other computers. It may serve data to systems on a local area network (LAN) or a wide area network (WAN) over the Internet.

Many types of servers exist, including web servers, mail servers, and file servers. Each type runs software specific to the purpose of the server. For example, a Web server may run Apache HTTP Server or Microsoft IIS, which both provide access to websites over the Internet.

A mail server may run a program like Exim or iMail, which provides SMTP services for sending and receiving email. A file server might use Samba or the operating system's built-in file sharing services to share files over a network.

While server software is specific to the type of server, the hardware is not as important. In fact, a regular desktop computers can be turned into a server by adding the appropriate software. For example, a computer connected to a home network can be designated as a file server, print server, or both.

While any computer can be configured as a server, most large businesses use rack-mountable hardware designed specifically for server functionality. These systems, often 1U in size, take up minimal space and often have useful features such as LED status lights and hot-swappable hard drive bays.

Multiple rack-mountable servers can be placed in a single rack and often share the same monitor and input devices. Most servers are accessed remotely using remote access software, so input devices are often not even necessary.

While servers can run on different types of computers, it is important that the hardware is sufficient to support the demands of the server. For instance, a web server that runs lots of web scripts in real-time should have a fast processor and enough RAM to handle the "load" without slowing down. A file server should have one or more fast hard drives or SSDs that can read and write data quickly. 

Regardless of the type of server, a fast network connection is critical, since all data flows through that connection.

CLOUD SERVER HOSTING

Cloud server hosting is a type of hosting in which hosting services are made available to customers on demand via the Internet.  Rather than being provided by a single server or virtual server, cloud server hosting services are provided by multiple connected servers that comprise a cloud. Cloud server hosting is also sometimes referred to as cluster server hosting or server on-demand hosting.

Cloud server hosting offers the advantages of increased accessibility and reliability, seamless scalability and potential cost savings, as customers are freed from having to invest in on-premises servers and hardware, and they pay only for the resources they consume.  On the other hand, security and lack of access and full control are potential concerns with cloud server hosting

WEB SERVER

Web servers are computers that deliver (serves up) Web pages. Every Web server has an IP address and possibly a domain name. For example, if you enter the URL 

http://www.pcwebopedia.com/index.html in your browser, this sends a request to the Web server whose domain name is pcwebopedia.com. The server then fetches the page named index.html and sends it to your browser.

Any computer can be turned into a Web server by installing server software and connecting the machine to the Internet. There are many Web server software applications, including public domain software from NCSA and Apache, and commercial packages from Microsoft, Netscape and others

PROXY SERVER

A server that sits between a client application, such as a Web browser, and a real server. It intercepts all requests to the real server to see if it can fulfill the requests itself. If not, it forwards the request to the real server.

Proxy servers have two main purposes:

Improve Performance: Proxy servers can dramatically improve performance for groups of users. This is because it saves the results of all requests for a certain amount of time. Consider the case where both user X and user Y access the World Wide Web through a proxy server. First user X requests a certain Web page, which we'll call Page 1. 

Sometime later, user Y requests the same page. Instead of forwarding the request to the Web server where Page 1 resides, which can be a time-consuming operation, the proxy server simply returns the Page 1 that it already fetched for user X. Since the proxy server is often on the same network as the user, this is a much faster operation. 

Real proxy servers support hundreds or thousands of users. The major online services such as America Online, MSN and Yahoo, for example, employ an array of proxy servers.

Filter Requests: Proxy servers can also be used to filter requests. For example, a company might use a proxy server to prevent its employees from accessing a specific set of Web sites.

DEDICATED SERVER

A dedicated server is a single computer in a network reserved for serving the needs of the network. For example, some networks require that one computer be set aside to manage communications between all the other computers. 

A dedicated server could also be a computer that manages printer resources. Note, however, that not all servers are dedicated. In some networks, it is possible for a computer to act as a server and perform other functions as well.

In the Web hosting business, a dedicated server is typically a rented service. The user rents the server, software and an Internet connection from the Web host.

APPLICATION SERVER

Also called an appserver, an application server is a program that handles all application operations between users and an organization's backend business applications or databases.

An application server is typically used for complex transaction-based applications. To support high-end needs, an application server has to have built-in redundancy, monitor for high-availability, high-performance distributed application services and support for complex database access.

What are Proxy Servers?

The other day, I was searching for some proxy sites in order to get access to facebook which is blocked in my institute. After some search I did get a site but then arose a question in my mind: - What are proxy servers? 

Proxy servers, just like simple web servers, complete the requests made by clients. But the difference is that proxy servers don't have the resource that clients request for. A proxy server just connects clients to the main web server and acts as a middleman/ intermediary. It is like you trying to talk to your friend through a third person. Then the next question that came to my mind was: - Why do we need a proxy server then, can't we directly contact web servers to gain the required information ? Yes, we can but there are situations where using a proxy server is beneficial for a user as well as for organizations. 

Proxy Server Concept

Uses of Proxy Servers

Now that you have some idea about what a proxy server is, you may think that we don't need a proxy server if we can access some resource or file directly from a web server. But there are some inherit advantages of using a proxy server for a general user as well as organisations.

Due to various reasons, organisations and ISPs block access to various sites. This content filtering is made possible by proxy servers. So depending on the content access policies of the organisation, the network administrator can configure the settings of proxy servers.

Proxy Servers also help in improving the performance by addressing client requests faster. This is possible by use of cache. Consider that you access facebook often using proxy site. Then a friend of yours, on the same network, also tries to connect to facebook through the proxy site. Facebook homepage will now be saved in the proxy server’s cache rather than retrieving from remote server again and your friend will be able to access it faster.

Proxy Server helps in keeping the client's IP address anonymous, thus ensuring better security.

Although they help organisations in blocking sites and filtering content but at the same time, some proxies allow user to access blocked sites. Such proxies help the user get through various firewalls and controlling softwares which are installed to regulate access.

Proxies can be used to log internet usage within an office or by a particular user.

Proxy server can be used as firewall to scan outbound and inbound flow of data. Thus they also nullify chances of hacking.

I hope now you know the advantages of proxy servers. But a word of caution, proxy servers are difficult to configure and if not done properly, a hacker can exploit it to gain sensitive data.
P.S. Do share your experiences of using proxy sites from college or office. :)