Microsoft KB Archive/178022

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NetBIOS SEND WAIT Over TCP/IP Completes Without NetBIOS RECEIVE

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Q178022

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The information in this article applies to:


 * Microsoft Windows 95
 * Microsoft Windows 95 OEM Service Release, versions 1, 2, 2.1

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SYMPTOMS
When a program issues a synchronous NetBIOS SEND (SEND_WAIT) command using Transmission Control Protocol/Internet Protocol (TCP/IP) on a Windows 95- based computer, the command immediately returns indicating successful completion, even if the computer to which the command is sent does not receive the data at the NetBIOS layer. Specifically, the SEND command may be completed even if the recipient does not post a NetBIOS RECEIVE Network Control Block (NCB).

This may be a problem if the sending program terminates the session immediately after the synchronous SEND command is completed. If the recipient computer posts a NetBIOS RECEIVE NCB after it acknowledges the TCP/IP data, the sent data may no longer be available to be received.

CAUSE
The Microsoft TCP/IP protocol included with Windows 95 acknowledges the receipt of NetBIOS data before the data is received at the NetBIOS layer, even if a NetBIOS RECEIVE NCB has not been posted.

RESOLUTION
This issue is resolved by the following updated file for Windows 95 and OSR2, and later versions of this file:

  VTCP.386  version 4.00.955  dated 8/5/97  47,413 bytes A version of this file which resolves this problem is included in the Windows Sockets 2.0 update for Windows 95. For information on obtaining this update, see the following article in the Microsoft Knowledge Base:

"Q182108 Availability of Windows Sockets 2.0 for Windows 95"

STATUS
Microsoft has confirmed this to be a problem in Microsoft Windows 95 and OEM Service Release 2 (OSR2). An update to address this problem is now available, but is not fully regression tested and should be applied only to computers experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft does not recommend implementing this update at this time. Contact Microsoft Technical Support for additional information about the availability of this update.

This issue is resolved in Microsoft Windows 98.

MORE INFORMATION
This behavior is by design. However, the behavior of the NCBSENDWAIT command over TCP/IP is inconsistent with the behavior of the NCBSENDWAIT command over other protocols included with Windows 95 (such as Internetwork Packet Exchange/Sequenced Packet Exchange [IPX/SPX]- compatible protocol and NetBIOS Enhanced User Interface [NetBEUI] protocol). With other protocols, the NCBSENDWAIT command does not return until the recipient receives the data at the NetBIOS layer.

This behavior may be undesirable if a program sends NetBIOS data, then terminates as soon as the SEND command is returned. Instead, if the program posts a NetBIOS RECEIVE command and waits for the recipient to complete the receive, this behavior has no adverse impact.

For additional information about issues resolved by updates to this component, please see the following articles in the Microsoft Knowledge Base:

Q177539 Windows 95 Stops Responding Because of Land Attack

Q170791 Windows 95 TCP Clients Run Out of Ports

Q168747 Update to Windows 95 TCP/IP to Address Out-of-Band Issue

Q154579 Slow TCP/IP Performance When Resuming Large Data Transfer For additional information about Windows 95 updates, please see the following article in the Microsoft Knowledge Base:

"Q161020 Implementing Windows 95 Updates" Additional query words:

Keywords : kbnetwork osr2 win95 kbAPI kbNetBIOS kbSDKPlatform kbGrpDSNet

Issue type :

Technology : kbWin95search kbOPKSearch kbWin95 kbWin95OPKOSR2 kbWin95OPKOSR1 kbWin95OPKOSR210