6.1 Overview of Request/Response Communication

In request/response communication mode, one software module sends a request to a second software module and waits for a response. Because the first software module performs the role of the client, and the second, the role of the server, this mode is also referred to as client/server interaction. Many online banking tasks are programmed in request/response mode. For example, a request for an account balance is executed as shown in the following figure:

1. A customer (the client) sends a request for an account balance to the Account Record Storage System (the server).
2. The Account Record Storage System (the server) sends a reply to the customer (the client), specifying the dollar amount in the designated account.

Figure 6-1 Example of Request/Response Communication in Online Banking

Once a client process has joined an application, allocated a buffer, and placed a request for input into that buffer, it can then send the request message to a service subroutine for processing and receive a reply message.