TN5250 Clients May Fail with a STATE_CHECK Error

ID: Q220942

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

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:

Keywords : sna4sp3fix
Version : WINDOWS:3.0,3.0SP1,3.0SP2,3.0SP3,4.0,4.0SP1,4.0SP2
Platform : WINDOWS
Issue type : kbbug