Socket.EndAccept Method (Byte[], IAsyncResult)

Note: This method is new in the .NET Framework version 2.0.

Asynchronously accepts an incoming connection attempt and creates a new Socket object to handle remote host communication. This method returns a buffer that contains the initial data transferred.

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

public Socket EndAccept (
	out byte[] buffer,
	IAsyncResult asyncResult
public Socket EndAccept (
	/** @attribute OutAttribute() */ /** @ref */ byte[] buffer, 
	IAsyncResult asyncResult
JScript does not support passing value-type arguments by reference.



An array of type Byte that contains the bytes transferred.


An IAsyncResult object that stores state information for this asynchronous operation as well as any user defined data.

Return Value

A Socket object to handle communication with the remote host.

Exception typeCondition


Windows NT is required for this method.


The Socket object has been closed.


asyncResult is empty.


asyncResult was not created by a call to BeginAccept.


EndAccept method was previously called.


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

EndAccept completes a call to BeginAccept. Before calling BeginAccept, you need to create a callback method that is invoked by the AsyncCallback delegate. This callback method executes in a separate thread, and is called by the system after the BeginAccept method returns.

Within the callback method, call the AsyncState method of the asyncResult parameter to obtain the Socket on which the connection attempt is being made. After obtaining the Socket, you can call the EndAccept method to successfully complete the connection attempt. The buffer parameter of this overload contains the data that was received in the call to BeginAccept and the bytesTransferred parameter contains the number of bytes that were transferred in the call.

The EndAccept method blocks until a connection is pending in the incoming connection queue. The EndAccept method accepts the incoming connection and returns a new Socket that can be used to send data to and receive data from the remote host.


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 uses BeginAccept to create and connect a socket and accept the initial 10 bytes of data. The callback delegate calls EndAccept to end the asynchronous request. The number of bytes transmitted and the data are returned in the buffer and bytesTransferred parameters of this method and are displayed on the console.

    // This server waits for a connection and then uses asynchronous operations to
    // accept the connection with initial data sent from the client.
    // Establish the local endpoint for the socket.

    IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
    IPAddress ipAddress = ipHostInfo.AddressList[0];
    IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
    // Create a TCP/IP socket.
    Socket listener = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp );

    // Bind the socket to the local endpoint, and listen for incoming connections.

    while (true) 
        // Set the event to nonsignaled state.

        // Start an asynchronous socket to listen for connections and receive data from the client.
        Console.WriteLine("Waiting for a connection...");

        // Accept the connection and receive the first 10 bytes of data.
        int receivedDataSize = 10;
        listener.BeginAccept(receivedDataSize, new AsyncCallback(AcceptReceiveCallback), listener);
        // Wait until a connection is made and processed before continuing.

public static void AcceptReceiveCallback(IAsyncResult ar) 
    // Get the socket that handles the client request.
    Socket listener = (Socket) ar.AsyncState;
    // End the operation and display the received data on the console.
    byte[] Buffer;
    int bytesTransferred;
    Socket handler = listener.EndAccept(out Buffer, out bytesTransferred, ar);
    string stringTransferred = Encoding.ASCII.GetString(Buffer, 0, bytesTransferred);
    Console.WriteLine("Size of data transferred is {0}", bytesTransferred);
    // Create the state object for the asynchronous receive.
    StateObject state = new StateObject();
    state.workSocket = handler;
    handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,
    new AsyncCallback(ReadCallback), state);

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

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

.NET Framework

Supported in: 2.0

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