TS/MP 2.5 Pathsend and Server Programming Manual

4 Writing Pathway Servers
This chapter explains how to write server programs that service requests from Pathway requestors.
Such requestors can be Pathsend requestors, SCREEN COBOL requestors, or clients that use the
RSC/MP product or the POET product. Pathsend requestors are described in this manual. SCREEN
COBOL requestors 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, see the Remote Server Call (RSC) Programming
Manual. For information about writing POET clients, see 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 must be
familiar with the Guardian requestor/server model and with the $RECEIVE mechanism as
implemented in the programming language you are using.
NOTE: This chapter 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 more information, see the Open System Services
Programmer’s Guide.
If you are using the TMF subsystem, you must 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 69), later in this chapter, 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 Requestors
The protocol for Pathway server processes is essentially the same regardless of the type of requestor
with which they work. Therefore, Pathway servers can be used by more than one type of requestor;
for example, by both Pathsend requestors and SCREEN COBOL requestors, or by both Guardian
requestors and clients from client/server environments. If servers are used by several types of
requestor, the server program request and reply formats must be consistent with that of all the
requestors.
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 the messages directly from a requestor
program, but instead receives them from an intermediate process: an ACS subsystem ROUT process
or a TCP. Whereas a Guardian server receives open messages, I/O messages, and close messages
from the requestor, a Pathway server receives all these messages from an ACS subsystem ROUT
process or the TCP. A Pathway server receives no information about the identity of the requestor
process that initiated the communication, unless the requestor provides that information in the
messages it sends.
Basic Pathway Server Programming 61