TS/MP Pathsend and Server Programming Manual (H06.05+, J06.03+)

4 Writing Pathway Servers
This section explains how to write server programs that service requests from Pathway requesters.
Such requesters can be Pathsend requesters, SCREEN COBOL requesters, or clients that use the
RSC/MP product or the POET product. Pathsend requesters are described in this manual. SCREEN
COBOL requesters are described in the Pathway/iTS TCP and Terminal Programming Guide; the
SCREEN COBOL language is described in the Pathway/iTS SCREEN COBOL Reference Manual.
For information about writing RSC/MP clients, refer to the Remote Server Call (RSC) Programming
Manual. For information about writing POET clients, refer to the Pathway Open Environment Toolkit
(POET) Programming Manual.
Pathway server programs read requests from $RECEIVE, as described in the Guardian Programmer’s
Guide and in the manuals describing HP programming languages. You can write Pathway server
programs in C, C++, COBOL85, Pascal, pTAL, TAL, FORTRAN, or Extended BASIC. You should
be familiar with the Guardian requester/server model and with the $RECEIVE mechanism as
implemented in the programming language you are using.
NOTE: This section describes how to write Pathway servers in the Guardian environment. You
can also write a Pathway server program in the OSS environment. The basic design considerations
in this section apply also to Pathway servers in the OSS environment; however, additional OSS
programming considerations also apply. For information about these programming considerations,
refer to the Open System Services Programmer’s Guide.
If you are using the TMF subsystem, you should also be familiar with general programming
guidelines and considerations for TMF servers, as described in the HP NonStop Transaction
Management Facility (TMF) Application Programmer’s Guide.
Basic Pathway Server Programming
The simplest type of Pathsend server is a context-free server. This subsection provides information
related to writing context-free Pathway servers, as well as information that applies to all Pathway
servers. “Writing Context-Sensitive Servers” (page 70), later in this section, provides information
about the additional tasks required of a context-sensitive Pathway server.
In X/Open and NonStop Tuxedo system terminology, a context-free server is called a
request/response server, and a context-sensitive server is called a conversational server.
Servers Shared by Different Types of Requesters
The protocol for Pathway server processes is essentially the same regardless of the type of requester
they work with. Therefore, Pathway servers can be used by more than one type of requester; for
example, by both Pathsend requesters and SCREEN COBOL requesters, or by both Guardian
requesters and clients from client/server environments. If servers are used by several types of
requester, the server program request and reply formats must be consistent with that of all the
requesters.
Guardian Servers and Pathway Servers
Like a Guardian server, a Pathway server receives messages by reading the Guardian $RECEIVE
file. However, unlike a Guardian server, it does not receive its messages directly from a requester
program, but instead receives them from an intermediate process: a LINKMON process, ACS
subsystem processes, or a TCP. Whereas a Guardian server receives open messages, I/O messages,
and close messages from the requester, a Pathway server receives all these messages from the
LINKMON process, the ACS subsystem processes, or the TCP. A Pathway server receives no
information about the identity of the requester process that initiated the communication, unless the
requester provides that information in the messages it sends.
62 Writing Pathway Servers