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TcpListener.BeginAcceptTcpClient Method

Begins an asynchronous operation to accept an incoming connection attempt.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public IAsyncResult BeginAcceptTcpClient(
	AsyncCallback callback,
	Object state
)

Parameters

callback
Type: System.AsyncCallback

An AsyncCallback delegate that references the method to invoke when the operation is complete.

state
Type: System.Object

A user-defined object containing information about the accept operation. This object is passed to the callback delegate when the operation is complete.

Return Value

Type: System.IAsyncResult
An IAsyncResult that references the asynchronous creation of the TcpClient.

ExceptionCondition
SocketException

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

ObjectDisposedException

The Socket has been closed.

NoteNote:

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

The asynchronous BeginAcceptTcpClient operation must be completed by calling the EndAcceptTcpClient method. Typically, the method is invoked by the callback delegate.

This method does not block until the operation completes. To block until the operation completes, use the AcceptTcpClient method.

For detailed information about using the asynchronous programming model, see Calling Synchronous Methods Asynchronously.

NoteNote:

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 http://msdn.microsoft.com/library/ for a detailed description of the error.

NoteNote:

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

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

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

// Accept one client connection asynchronously. 
public static void DoBeginAcceptTcpClient(TcpListener 
    listener)
{
    // Set the event to nonsignaled state.
    tcpClientConnected.Reset();

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

    // Accept the connection.  
    // BeginAcceptSocket() creates the accepted socket.
    listener.BeginAcceptTcpClient(
        new AsyncCallback(DoAcceptTcpClientCallback), 
        listener);

    // Wait until a connection is made and processed before  
    // continuing.
    tcpClientConnected.WaitOne();
}

// Process the client connection. 
public static void DoAcceptTcpClientCallback(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 console.
    TcpClient client = listener.EndAcceptTcpClient(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.
    tcpClientConnected.Set();

}
// Thread signal.
static ManualResetEvent* tcpClientConnected = 
    new ManualResetEvent(false);

// Accept one client connection asynchronously.
static void DoBeginAcceptTcpClient(TcpListener* listener)
{
    // Set the event to nonsignaled state.
    tcpClientConnected->Reset();

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

    // Accept the connection. 
    // BeginAcceptSocket() creates the accepted socket.
    listener->BeginAcceptTcpClient(
        new AsyncCallback(0, 
                        &tcplistener::DoAcceptTcpClientCallback), 
        listener);

    // Wait until a connection is made and processed before
    // continuing.
    tcpClientConnected->WaitOne();
}

// Process the client connection.
static void DoAcceptTcpClientCallback(IAsyncResult* ar) 
{
    // Get the listener that handles the client request.
    TcpListener* listener = 
        dynamic_cast<TcpListener*> (ar->AsyncState);

    // Get the new TcpClient.
    TcpClient* client = listener->EndAcceptTcpClient(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.
    tcpClientConnected->Set();
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

Supported in: 3.5, 3.0, 2.0

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