HP-UX SNAplus2 R7 LUA Programmer's Guide

Concepts
A Sample LUA Communication Sequence
The SLI example shows the same sequence of messages flowing between the host and the application. The SLI
verbs used are similar to those used in the RUI example, but note the following differences:
• SLI_OPEN handles the complete session initialization; the application does not need to read and write each
individual RU in the initialization sequence, as in the RUI example.
• LUA uses the application’s BIND and SDT routines (specified on SLI_OPEN) to allow the application to process
the BIND and SDT messages from the host. These routines must return synchronously. All other SLI verbs
complete asynchronously.
• SLI_RECEIVE and SLI_SEND handle complete chains of data, so the application needs only one verb to receive
or send the data even though it is long enough to require two or three RUs. (In the RUI example, the application
must receive or send each RU with a separate verb.)
The list that follows shows the abbreviations used in Figure 1–3,
RUI Communication Sequenceand Figure 1–4, SLI
Communication Sequence.
SSCP norm SSCP session, normal flow
LU norm LU session, normal flow
LU exp LU session, expedited flow
+rsp Positive response to the indicated message
BC Begin chain
MC Middle of chain
EC End chain
CD Change direction indicator set
RQD Definite response required
Figure 1–3, RUI Communication Sequence, shows the RUI verbs used to start a session, exchange data, and end the
session, and the SNA messages sent and received. The arrows indicate the direction in which SNA messages flow.
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