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Socket.EndConnect Method

Ends a pending asynchronous connection request.

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

public void EndConnect(
	IAsyncResult asyncResult


Type: System.IAsyncResult
An IAsyncResult that stores state information and any user defined data for this asynchronous operation.


asyncResult is null.


asyncResult was not returned by a call to the BeginConnect method.


EndConnect was previously called for the asynchronous connection.


An error occurred when attempting to access the socket. See the Remarks section for more information.


The Socket has been closed.

EndConnect is a blocking method that completes the asynchronous remote host connection request started in the BeginConnect method.

Before calling BeginConnect, you need to create a callback method that implements the AsyncCallback delegate. This callback method executes in a separate thread and is called by the system after BeginConnect returns. The callback method must accept the IAsyncResult returned by the BeginConnect method as a parameter.

Within the callback method, call the AsyncState method of the IAsyncResult parameter to obtain the Socket on which the connection attempt is being made. After obtaining the Socket, you can call the EndConnect method to successfully complete the connection attempt.


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


This member outputs trace information when you enable network tracing in your application. For more information, see Network Tracing.

The following code example ends the asynchronous connection attempt. For a complete example that demonstrates asynchronous communications with sockets, see Socket Code Examples.

     Socket s = (Socket) ar.AsyncState;
     StateObject so2 = new StateObject();
     so2.workSocket = s;
     byte[] buff = Encoding.ASCII.GetBytes("This is a test");
     s.BeginSend(buff, 0, buff.Length,0,
	                       new AsyncCallback(Async_Send_Receive.Send_Callback), so2);    

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.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.