The client in client-server architecture

There is no upper bound on the number of clients that can be serviced by a single server. It is also not mandatory that the client and server should reside in separate systems. Both client and server can reside in the same system, based on the hardware configuration of the system and the type of functionality or service provided by the server. The communication between client and server happens through the exchange of messages using a request-response pattern. The client basically sends a request for a service, and the server returns a response. This request-response pattern of communication is an excellent example of inter-process communication. For this communication to happen efficiently, it is necessary to have a well-defined communication protocol that lays down the rules of communication, such as the format of request messages, response messages, error handling, and so on. All communication protocols that are used for client-server communication work in the application layer of the protocol stack. To further streamline the process of client-server communication, the server sometimes implements a specific API that can be used by the client for accessing any specific service from the server.