Introduction to Networking for NonStop S-Series Servers

Application Programming With Communications
Products
Introduction to Networking for HP NonStop S-Series Servers—520670-005
3-8
Requester-Server Model
Requester-Server Model
The relationship between your application and a HP communications product reflects
an architectural concept called the requester-server model. When you run an
application program on the NonStop S-series server, the NonStop Kernel operating
system creates a user process. User processes make requests of a communications
subsystem through file-system calls to a subsystem process. Even if your application
does not make file-system calls directly, your statements are translated internally into
file-system calls. The subsystem process accepts the requests, performs the
requested action, and then returns the status of the operation to the application
process through the file system. The subsystem process then waits for another
request.
Within the context of the requester-server model, HP communications products support
several kinds of relationships between the application process on the NonStop S-series
server and an external device or system:
•
The application can be a requester, controlling the external device or system as an
application resource. In this case, the application opens the external device or
system in order to use it. This is the most common model for HP communications
products.
•
The application can serve an external device or system. In this case, the
application waits for an external device or system to request to use it. The HP
communications product receives the initiation request and informs the application,
which then establishes a session with the external requester.
Note. If you are familiar with client-server architecture, the HP original requester-server design
might look very familiar to you. The requester-server architecture is conceptually the same as
the client-server architecture.