TcpListener.EndAcceptSocket Method (IAsyncResult)


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Asynchronously accepts an incoming connection attempt and creates a new Socket to handle remote host communication.

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

public Socket EndAcceptSocket(
	IAsyncResult asyncResult


Type: System.IAsyncResult

An IAsyncResult returned by a call to the BeginAcceptSocket method.

Return Value

Type: System.Net.Sockets.Socket

A Socket.

The Socket used to send and receive data.

Exception Condition

The underlying Socket has been closed.


The asyncResult parameter is null.


The asyncResult parameter was not created by a call to the BeginAcceptSocket method.


The EndAcceptSocket method was previously called.


An error occurred while attempting to access the Socket. See the Remarks section for more information.

This method blocks until the operation is complete. To perform this operation synchronously, use the AcceptSocket method.


You can call the RemoteEndPoint property of the returned Socket to identify the remote host's network address and port number.


If you receive a SocketException, use the SocketException.ErrorCode property to obtain the specific error code and refer to the Windows Sockets version 2 API error code documentation in the MSDN library at 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 in the .NET Framework.

The following code example demonstrates the use of the BeginAcceptSocket method to create and connect a socket. The callback delegate calls the EndAcceptSocket method to end the asynchronous request.

// Thread signal.
public static ManualResetEvent clientConnected = 
    new ManualResetEvent(false);

// Accept one client connection asynchronously.
public static void DoBeginAcceptSocket(TcpListener listener)
    // Set the event to nonsignaled state.

    // Start to listen for connections from a client.
    Console.WriteLine("Waiting for a connection...");

    // Accept the connection. 
    // BeginAcceptSocket() creates the accepted socket.
        new AsyncCallback(DoAcceptSocketCallback), listener);
    // Wait until a connection is made and processed before 
    // continuing.

// Process the client connection.
public static void DoAcceptSocketCallback(IAsyncResult ar) 
    // Get the listener that handles the client request.
    TcpListener listener = (TcpListener) ar.AsyncState;

    // End the operation and display the received data on the
    Socket clientSocket = listener.EndAcceptSocket(ar);

    // Process the connection here. (Add the client to a 
    // server table, read data, etc.)
    Console.WriteLine("Client connected completed");

    // Signal the calling thread to continue.

.NET Framework
Available since 2.0
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