Client and server roles in HCL Marketing Software
HCL® Marketing Software application components can act as either the client or the server in a communication, depending on the situation.
Most HCL Marketing Software applications consist of two parts.
The web application. The web application is the component that users access through a browser.
The server (for example, the Campaign listener and the Marketing Platform API server). This component is accessed programmatically.
The following examples and diagrams illustrate the roles played by HCL® components in various communications.
Example 1 - Communication between a browser and an HCL Marketing Software web application
When users communicate with HCL Marketing Software web applications through a browser, the browser is the client and the HCL Marketing Software web application is the server.

Example 2 - Communication between components of one HCL Marketing Software application
The two components of a single HCL Marketing Software application can also communicate with each other programmatically. For example, when the Campaign web application sends a request to the Campaign listener, the Campaign web application is the client and the listener is the server.

Example 3 - HCL Marketing Software components playing both roles
An HCL Marketing Software application component can communicate as a client in some exchanges and as a server in others. An example of these relationships is shown in the following diagram.
