DOCUMENT:Q160876  12-JUN-2001  [sna]
TITLE   :INFO: SNA Server Does Not Support Full Duplex APPC
PRODUCT :Microsoft SNA Server
PROD/VER:WINDOWS:2.0,2.1,2.11,3.0,4.0
OPER/SYS:
KEYWORDS:kbnetwork kbprogramming

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The information in this article applies to:

 - Microsoft SNA Server, versions 2.0, 2.1, 2.11, 3.0, 4.0 
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SUMMARY
=======

APPC is a peer-oriented program-to-program API where either Transaction Program
(TP) can initiate a conversation. However, APPC/LU6.2 traditionally is
half-duplex, where after the conversation is established, only one TP has
direction to send on a conversation at a time. The state of the conversation, as
viewed by a particular TP, governs which APPC verbs can be issued by the TP at a
particular time. If the local TP views the conversation as being in a "send"
state, then the partner TP would also be in a send state.

IBM now supports "full duplex" APPC where either program can issue both send and
receive verbs at the same time, though this is a fairly new implementation of
APPC.

The following is the option to set for full duplex functionality:

   112 -- Full-duplex conversations and expedited data

SNA Server does not support option set 112; it only supports half-duplex,
although either end can initiate the conversation.

MORE INFORMATION
================

See the "Conversation States" section of Chapter 2 of the SNA Server
Programmer's Reference for a thorough explanation of conversation state changes.

Additional query words:

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Keywords          : kbnetwork kbprogramming 
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ200 kbSNAServ211 kbSNAServ400 kbSNAServ210
Version           : WINDOWS:2.0,2.1,2.11,3.0,4.0
Issue type        : kbinfo

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