What are clients, servers, hosts, and nodes?

When talking about clients, servers, hosts, and nodes, we are actually talking about computer network components. At first glance, it may seem like, more or less, we are talking about the same component, but in fact each component is unique in itself. Hence, to understand these components correctly, the following sections will explain clients, servers, hosts, and nodes.

Understanding clients and servers

As you may know, the network world recognizes two architectures: peer-to-peer (P2P) and client/server architecture. While a P2P network architecture consists of hosts that, depending on network activity, switch roles from client to server and vice versa, in a client/server architecture, hosts have predefined roles where some are clients and some are servers. Clients are the hosts who make requests for network services, whereas the servers are hosts that provide network services. Both clients and servers play an active role in computer networks. In Figure 1.5, the server with a shared printer acts as a print server, and as such it provides print services to the clients in a network. Whereas, the PC, laptop, and smartphone represent the clients that request services:

Figure 1.5 Client/server network architecture

The origin of the word server originates from the word serve. If you search for the word serve in the Merriam-Webster dictionary, among the results you will find is the one that says: to provide services that benefit or help. Thus, a server in a computer network means a computer that provides services to the clients. From that, the server serves the clients.

Understanding hosts and nodes

When talking about hosts and nodes, although their first impression might drive us towards thinking that they are the same thing, in fact, they are not! The difference between hosts and nodes is that while all hosts can be nodes, not every node can act as a host. That way, to every host an IP address is assigned. So, a host is any device with an IP address that requests or provides networking resources to any other host or node on the network. However, there are devices such as hubs, bridges, switches, modems, and access points that have no IP address assigned, but are still used for communication. That said, a node is any device that can generate, receive, and transmit the networking resources on a computer network, and as such it has no communication interface with an IP address. Based on that, in Figure 1.5, the server, smartphone, PC, and laptop are acting as hosts in a network, while the switch and access point (AP) act as nodes.