Article ID: 173619 - View products that this article applies to.
This article was previously published under Q173619
The Winsock control will get an error after a Connect method is called if the same local port has been used within the past four minutes.
The Windows socket control does not have the ability to set the socket option SO_REUSEADDR. This option allows the socket to be bound to an address that is already in use.
When you close the handle to a socket, some additional negotiation goes on between the client and the server. The socket will wait for up to two times the maximum time that windows would wait to receive an acknowledgement from the other end of the socket that closed the port. By default, this option is set to two minutes. Therefore, Windows may wait up to four minutes before the port is actually released.
This makes that specific port unavailable until it is actually released.
The only workaround is to not use a specific local port. If you set the LocalPort property to Zero, Winsock will pick a random local port for you and use it until a Close method is called on the WinSock Control.
Setting the LocalPort property of the socket to Zero, will cause Windows to pick a random port.
To do this, place the following code just before the line that does the connect:
Steps to Reproduce BehaviorThe following sample demonstrates how to reproduce the issue and how to work around it. In the code "myserver" indicates any Windows 2000 or Windows NT Server running Simple TCP/IP Services, which includes an Echo server on Port 7.
Article ID: 173619 - Last Review: April 28, 2000 - Revision: 1.0