Microsoft KB Archive/184505

= CPI-C Accept_Conversation (cmaccp) Does Not Block As Expected =

Article ID: 184505

Article Last Modified on 3/8/2005

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APPLIES TO


 * Microsoft SNA Server 2.0
 * Microsoft SNA Server 2.1
 * Microsoft SNA Server 3.0
 * Microsoft SNA Server 3.0 Service Pack 4
 * Microsoft SNA Server 4.0

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This article was previously published under Q184505



SYMPTOMS
If a CPI-C (Common Programming Interface for Communications) application calls WinCPICStartup followed by Accept_Conversation (cmaccp), then the cmaccp will function in blocking mode. However, the cmaccp will never complete, because no local TP (transaction processing) name has been specified for the application.

In order to associate a TP (Transaction Program) name with the cmaccp call, Specify_Local_TP_Name (cmsltp) must be called prior to cmaccp. However, this causes cmaccp to function in "non-blocking" mode. This can cause the cmaccp to fail immediately with an error 25 (CM_PROGRAM_STATE_CHECK) instead of waiting for an incoming attach request.



CAUSE
This behavior is by design, according to the Windows CPI-C specification.



RESOLUTION
To force blocking behavior of cmaccp, Wait_For_Conversation (cmwait) must be called after cmsltp and cmaccp in order to cause the application's thread to block. All CPI-C functions operate in blocking mode by default, except the cmaccp function, which requires the application to call cmwait in order to force blocking behavior.

There are no plans to change the Windows CPI-C specification or to modify the SNA Server CPI-C API (application programming interface) to behave differently than it does in the current design.

Keywords: kbprb KB184505

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