A server program is a type of computer software that provides functionality to other programs or devices, called clients. The server accepts requests from clients and returns responses accordingly. Server programs are essential components of most computer networks, enabling networked devices to share data and access applications.
Some of the most common server programs include web servers, file servers, database servers, email servers, print servers, and application servers. These server programs receive requests over a network, perform specific operations or retrieve data, and return results to clients. Servers typically run continuously in the background and wait for client requests.
Web Servers
One of the most ubiquitous server programs is a web server. A web server stores web pages and other files used in websites. When a user opens a website in their web browser (the client), the browser sends a request to the web server for the required files. The web server then sends the requested HTML, CSS, JavaScript, images, and videos back to display the fully rendered website in the user’s browser.
Popular web servers include Apache HTTP Server, Microsoft Internet Information Services (IIS), and Nginx. Apache and Nginx are open source web servers that run on Unix-like systems, while IIS is developed by Microsoft for Windows servers. The basic function of all web servers is the same – receive HTTP requests from clients and return web pages or files.
Web servers require maintenance and configuration to serve website content quickly and securely to many users. Performance tuning, security measures, HTTPS encryption, and load balancing are common administration tasks for production web servers.
Dynamic vs Static Websites
Some web servers only serve static file content, while others support server-side scripting for dynamic websites. For example, servers like Apache and Nginx can be configured to process PHP, Python, Ruby, or other scripts to generate web pages on the fly. This allows for customized page content and database integration.
Static websites have fixed, pre-built HTML files for all pages. Dynamic sites generate page content at runtime using server-side technologies and databases. Both static and dynamic websites rely on web servers to deliver the resulting page content to visitors.
File Servers
A file server stores files that can then be accessed by clients over a network. This centralizes file storage and sharing services for an organization. Users can access, create, update, delete, and manage files on the file server from their networked devices.
File servers often use network file sharing protocols like SMB/CIFS for Windows clients or NFS for Unix-like systems. This enables client devices to mount remote file server directories and drives for transparent file access. File servers may also allow FTP access or shared Web access to files.
Common file server platforms include Windows Server with SMB file sharing enabled, and Linux/Unix servers running NFS server software. File server administration involves disk storage allocation, access permissions, backup routines, and ensuring high availability.
Advantages of File Servers
Central file servers offer important advantages for businesses compared to standalone PCs:
– Centralized files for easy collaboration and sharing
– Regular backups to protect data
– High availability with redundancy and failover
– Scalability to add storage as needed
– Role-based access controls and permissions
– Streamlined administration instead of managing files on each PC
Database Servers
A database server manages databases containing organized data like sales transactions, customer details, inventory, etc. Database management software runs on the server, allowing clients to store, modify, query, and retrieve information from the database.
Some common database server platforms include MySQL, PostgreSQL, Microsoft SQL Server, Oracle Database, and MongoDB. These servers support client connections over a network, user authentication, concurrency control, data integrity checking, backup tools, access permissions, and more.
Database administrators configure database servers for optimal performance and security. Important responsibilities include designing logical data models, capacity planning, writing stored procedures, tuning complex queries, and preventing unauthorized data access. Most enterprise applications rely on backend database servers for structured data management.
Relational vs. Non-Relational Databases
Traditional relational database servers like MySQL use rigid data schemas and table relations. Non-relational NoSQL database servers like MongoDB use flexible document storage, without predefined schemas. Relational databases excel at complex queries and transactions. NoSQL databases scale better for unstructured data like social media posts. Large organizations often use both relational and NoSQL databases for different needs. The servers provide standardized methods for clients to utilize these distinct database types.
Email Servers
Email servers are specialized programs that send, receive, and store email messages. When a user sends an email, their mail client contacts the outgoing email server to relay the message. This server communicates with the recipient’s incoming email server to deliver the email. The recipient then retrieves the email from their email server when they check their inbox.
Common email server platforms include Postfix, Sendmail, and Microsoft Exchange Server. These programs use SMTP for sending emails and IMAP/POP3 for receiving emails. Email servers may have anti-spam and anti-virus filters configured. They also support email access on a variety of client devices and platforms.
Webmail Servers
In addition to desktop mail clients, many users access email through web browsers. For this functionality, webmail server programs like SquirrelMail or Roundcube provide browser-based email access. The webmail server software still utilizes the main SMTP/IMAP email server in the backend.
Print Servers
A print server is a centralized hub that connects printers to client computers over a network. It allows many network users to share printers instead of directly connecting printers to individual machines. The print server spools and queues up print jobs, providing an efficient management system.
Print server software runs on Windows and Linux platforms. Common examples include CUPS on Linux and Print Services for UNIX on Windows Server. Many dedicated print server appliances are also available.
When a client prints a document, the print data is sent to the print server. The server software queues the job and dispatches it to the appropriate printer. Print servers improve printer access, sharing, security, and management for organizations.
Print Server Benefits
Key benefits of using print servers include:
– Centralized printer access and sharing
– Reduced printer setup and maintenance
– Streamlined driver installation
– Granular user permissions and accounting
– Rules to lower costs like duplex printing
Application Servers
Application servers occupy an important role in enterprise environments. They host applications and services that are then accessed by clients over a network. This offloads resource-intensive processing away from client devices.
For example, almost all websites rely on web application servers like Apache Tomcat, Nginx, and JBoss. These provide a runtime environment for Java, Ruby, PHP, or .NET applications. Game servers allow multiplayer games to be played online. Media servers stream audio and video content to many simultaneous viewers.
Application servers provide centralized facilities like load balancing, security, high availability, clustering, caching, and more. They host the backend business logic that powers large, complex applications and websites. Different application servers excel at particular programming languages, frameworks, or vendor ecosystems.
Middleware Servers
Middleware servers occupy the space between clients and backend application servers. They provide supporting capabilities like message queuing, monitoring, service orchestration, data transformations, and managing API calls. Middleware servers include offerings like Red Hat JBoss Middleware.
Virtualization and Cloud Servers
Most server programs run on dedicated physical server hardware. But virtualization and cloud technologies are now commonly used to deploy servers.
Virtualization allows multiple virtual servers to run on a single physical machine. Each virtual server acts as an independent system. The virtualization software like VMware ESXi abstracts and partitions the underlying hardware resources.
Cloud hosting services allow users to run servers on remote infrastructure administered by the cloud provider. Cloud servers can be quickly provisioned through a control panel or API.Providers like Amazon AWS, Microsoft Azure, and Google Cloud Platform offer cloud-based virtual servers.
Server Operating Systems
The operating system provides the foundation and environment for server programs to run on. Some common server OS platforms include:
– Windows Server – Popular proprietary OS for Windows-based servers
– Linux – Open-source Unix-like OS powering many web servers
– FreeBSD – Advanced open-source Unix OS optimized for servers
– Solaris – Enterprise Unix OS developed by Oracle
– macOS Server – Apple’s OS for Mac-based servers
These operating systems enable efficient server management and performance for applications like web serving, remote desktop access, storage, virtualization, email, DNS, and more.
Conclusion
Server programs and operating systems provide specialized capabilities optimized for serving many remote clients simultaneously. While desktop OS focuses on usability, server OS focuses on stability, scalability, and security. Server programs likewise excel at responsiveness, uptime, heavy loads, and advanced administration.
Web servers, file servers, database servers, email servers, print servers, and application servers are critical network building blocks. They centralize resources for efficiency, sharing, backups, and centralized management. Virtualization and cloud servers enable flexible server deployment with automation.
Understanding common server roles assists with architecture, sizing, capacity planning, troubleshooting, and maintaining the demanding performance and reliability expected of servers. Mastering server software is crucial to administering enterprise networks and infrastructure.
