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Q198663: BUG: Closesocket() on a Duplicated Socket Fails to Clean Up

Article: Q198663
Product(s): Microsoft Windows 95.x Retail Product
Version(s): WINDOWS:95,98
Operating System(s): 
Keyword(s): kbWinsock
Last Modified: 17-DEC-2000

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The information in this article applies to:

- Microsoft Windows 95 
- Microsoft Windows 98 
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SYMPTOMS
========

On Windows 95 and Windows 98, after launching a few WinSock applications using
the WSADuplicateSocket() function, you will no longer able to create a socket
connection. An attempt to call connect() function fails with the following error
message:

  WSAENOBUFS

CAUSE
=====

For a duplicated TCP socket on Windows 95 and Windows 98, the closesocket()
function fails to close the connection of the duplicated socket. This can be a
problem when you launch several (10 to 20) applications which use
WSADuplicateSocket() to create a duplicate socket and call closesocket() to
clean up the connection. It eventually exhausts all the socket resources. Using
the NETSTAT -AN command shows the maximum number of sockets already in use and
most of them are either in CLOSE_WAIT or FIN_WAIT_2 state indefinitely. At this
point, any attempt to call connect() will fail with error WSAENOBUFS since there
is no more socket available for a new connection.

By default, Windows 95 and Windows 98 TCP/IP stack allows a maximum number of 100
TCP sockets to open concurrently. This includes the TCP sockets in
waiting-for-close status. The same problem exists in Windows 95 when an
application uses the Winsock 1.1 DuplicateHandle() function. This problem does
not occur with Windows NT since it successfully cleans up the TCP connection
when calling closesocket() on a duplicated socket.

RESOLUTION
==========

The workaround would require the child application to create a dummy TCP socket
(just call socket (AF_INET, ,,,)) and close it at its own leisure. The other
possibility is to close the socket that is being duplicated in the parent
process only after child is done with it.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

Additional query words: kbDSupport WSADuplicateSocket

======================================================================
Keywords          : kbWinsock 
Technology        : kbWin95search kbWin98search kbZNotKeyword3 kbWin98
Version           : WINDOWS:95,98
Issue type        : kbbug
Solution Type     : kbnofix

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