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Q220942: TN5250 Clients May Fail with a STATE_CHECK Error

Article: Q220942
Product(s): Microsoft SNA Server
Version(s): WINDOWS:3.0,3.0SP1,3.0SP2,3.0SP3,4.0,4.0SP1,4.0SP2
Operating System(s): 
Keyword(s): kbsna400sp3fix
Last Modified: 08-MAY-2002

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The information in this article applies to:

- Microsoft SNA Server, versions 3.0, 3.0SP1, 3.0SP2, 3.0SP3, 4.0, 4.0SP1, 4.0SP2 
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SYMPTOMS
========

TN5250 clients of the the SNA Server TN5250 service may fail with a STATE_CHECK
AP_SEND_DATA_NO_LL_BDY, because of the way the datastream is interpreted.

CAUSE
=====

The TN5250 data stream that is exchanged is composed of a header followed by the
5250 client data stream. The header is variable in length and composed of two
parts:

- A fixed part

  This is six octets long and contains the logical record length, record type,
  and a reserved field.

- A variable part

  This includes a one-octet length field, flags, and an opcode field. The opcode
  field indicates the operation requested (for example, get/put/read
  immediate).

The 5250 client data stream follows, and is terminated by two octets, (IAC) with
value 0xFF, and (EOR) with value 0xFF. The (IAC) (EOR) combination marks the end
of the record. To uniquely identify these two octets as the termination, each
0xFF in the data stream is doubled.

The problem occurs when the doubled IAC character 0xFF sent by the emulator is
exactly between the two SEND buffers (first one ends with FF and second one
begins with the remaining FF). The TN5250 translator fails to undouble it
(0xFFFF should become 0xFF), so an extra character is sent to APPC. APPC is
waiting for a SEND buffer with n characters, and receives a send buffer with n+1
characters. This behavior generates a STATE_CHECK AP_SEND_DATA_NOT_LL_BDY.

RESOLUTION
==========

To resolve this problem, obtain the latest service pack for SNA Server version
4.0. For additional information, please see the following article in the
Microsoft Knowledge Base:

  Q215838 How to Obtain the Latest SNA Server Version 4.0 Service Pack


STATUS
======

Microsoft has confirmed this to be a problem in SNA Server 3.0, 3.0 SP1, 3.0
SP2, 3.0 SP3, SNA Server 4.0, 4.0 SP1, 4.0 SP2. This problem was first corrected
in SNA Server version 4.0 Service Pack 3.

Additional query words:

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Keywords          : kbsna400sp3fix 
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ400
Version           : WINDOWS:3.0,3.0SP1,3.0SP2,3.0SP3,4.0,4.0SP1,4.0SP2
Issue type        : kbbug
Solution Type     : kbfix

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