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UdpClient.DropMulticastGroup Method (IPAddress, Int32)

Leaves a multicast group.

Namespace:  System.Net.Sockets
Assembly:  System (in System.dll)

public void DropMulticastGroup(
	IPAddress multicastAddr,
	int ifindex


Type: System.Net.IPAddress
The IPAddress of the multicast group to leave.
Type: System.Int32
The interface index associated with the local IP address joined to the multicast group.


The underlying Socket has been closed.


An error occurred when accessing the socket. See the Remarks section for more information.


The IP address is not compatible with the AddressFamily value that defines the addressing scheme of the socket.


multicastAddr is null.

The DropMulticastGroup method withdraws the UdpClient from the multicast group identified by the specified IPAddress. After calling the DropMulticastGroup method, the underlying Socket sends an Internet Group Management Protocol (IGMP) packet to the router, removing the router from the multicast group. After a UdpClient withdraws from the group, it will no longer be able to receive datagrams sent to that group.


If you receive a SocketException, use the SocketException.ErrorCode property to obtain the specific error code. After you have obtained this code, you can refer to the Windows Sockets version 2 API error code documentation in MSDN for a detailed description of the error.

The following code example demonstrates how to drop a multicast group by providing a multicast address.

      // Send data to ClientTarget.
      Console.WriteLine("\nThe ClientOriginator sent:\n");
      Send.OriginatorSendData(clientOriginator, m_ClientTargetdest);

      // Receive data from ClientTarget
      Ret = Receive.ReceiveUntilStop(clientOriginator);

      // Stop the ClientTarget thread

      // Abandon the multicast group.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.