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Consider the following scenario:

  • You run a Microsoft .NET Framework 3.0-based or .NET Framework 3.5-based Windows Communication Foundation (WCF) service.

  • The WCF service uses the Net.Tcp Port Sharing Service (Smsvchost.exe) and is hosted on a computer that is running Internet Information Services (IIS).

  • One of the following conditions is true:

    • The CPU usage is high on the computer that is running IIS.

    • A throttle occurs in a service model for the WCF service.

    • Multiple requests are sent to the WCF service at the same time.

In this scenario, the WCF service takes longer than one minute to process a request from a client application. Additionally, an error message that assembles the following event entry is logged in the event log:

Log Name: System

Source: SMSvcHost


Event ID: 8

Task Category: Sharing Service

Level: Error

Keywords: Classic



Description: An error occurred while dispatching a duplicated socket: this handle is now leaked in the process.

ID: 2620

Source: System.ServiceModel.Activation.TcpWorkerProcess


System.TimeoutException: This request operation sent to did not receive a reply within the configured timeout (00:01:00). The time allotted to this operation may have been a portion of a longer timeout. This may be because the service is still processing the operation or because the service was unable to send a reply message. Please consider increasing the operation timeout (by casting the channel/proxy to IContextChannel and setting the OperationTimeout property) and ensure that the service is able to connect to the client.

Note You must restart IIS to recover the WCF service from this issue.


This issue occurs because the Smsvchost.exe process times out after one minute when it tries to transfer an incoming connection request to the W3wp.exe worker process. Additionally, this time-out is non-configurable.

When the CPU has a heavy workload, or when many concurrent connection requests are incoming, the Smsvchost.exe process cannot transfer the incoming connection to the W3wp.exe worker process within one minute. Therefore, the Smsvchost.exe process times out and eventually stops responding. When this issue occurs, the Smsvchost.exe process cannot route later requests to the W3wp.exe worker process until IIS is restarted.


To resolve this issue, apply hotfix 2504602 that is described in Microsoft Knowledge Base (KB) article.

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

2504602 A hotfix rollup package is available for WCF in the .NET Framework 3.0 SP2, in the .NET Framework 3.5 SP1 and in the .NET Framework 4


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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