Building Distributed
Applications
Using the Progress AppServer


Connection Operation

The way an AppServer connection works depends partly on the AppServer operating mode. For more information on operating modes, see the "Understanding AppServer Operating Modes" section. In general, a client application initiates the connection with an AppServer and manages the connection following these steps:

  1. The client application notifies the Progress Interface to send a connection request for a specified Application Service to a specified NameServer. The Progress Interface then sends the request to the NameServer, which the Progress Interface identifies using a host and port provided by the client application:
  2. If you have configured fault-tolerant NameServers, the replicated or neighbor NameServers attempt to resolve the connection. If no such NameServer can resolve the connection, the client receives a connection error.

  3. The resolving NameServer chooses a particular AppServer instance that supports the specified Application Service (and that balances client load, if so configured) and provides the Progress Interface with the network address of the Application Broker for that AppServer:
  4. The Progress Interface then sets up a connection with the Application Broker:
  5. The Application Broker either maintains the connection directly between itself and the client or provides the Progress Interface with the address of a particular Application Server process to which it can connect. Whether the Application Broker maintains the connection or hands the connection off to an Application Server process depends on the operating mode:
  6. Once the connection is established, all remote procedure requests from that client are sent over this connection.
  7. When the client no longer needs the connection, it disconnects from the AppServer by notifying the Progress Interface to send a disconnect request.

For more information on how to set up and work with a connection, see Programming the Client Application."


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