Release 10.1A: OpenEdge Application Server:
Developing AppServer Applications

> ## AppServer and Client Interaction

> This chapter describes how the AppServer™ supports interaction with a client to provide general purpose application services and how a client can interact with an AppServer to access these application services. The basis of AppServer support for client interaction is the AppServer operating mode, which determines how client requests can be processed by the AppServer. The AppServer supports any one of four possible operating modes. Depending on the operating mode, the interaction between the AppServer and client conforms to one of two possible session models:

> - Session-managed — Where a single AppServer handles all requests from a single client to a single application service, and the client manages a physical connection to the AppServer.

> - Session-free — Where one or more AppServers can handle all requests from a single client to a single application service, and the client manages no physical connection to any single AppServer.

> Regardless of the operating mode, a client can invoke synchronous or asynchronous requests to the AppServer, which the client manages depending on the session model.

> The following sections describe all of these elements of AppServer-client interaction:

> - Understanding AppServer operating modes

> - Session models and application services

> - Understanding synchronous and asynchronous requests

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