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TcpClient.BeginConnect Method (String, Int32, AsyncCallback, Object)

Begins an asynchronous request for a remote host connection. The remote host is specified by a host name (String) and a port number (Int32).

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

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public IAsyncResult BeginConnect(
	string host,
	int port,
	AsyncCallback requestCallback,
	Object state
)

Parameters

host
Type: System.String

The name of the remote host.

port
Type: System.Int32

The port number of the remote host.

requestCallback
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 that contains information about the connect operation. This object is passed to the requestCallback delegate when the operation is complete.

Return Value

Type: System.IAsyncResult
An IAsyncResult object that references the asynchronous connection.

ExceptionCondition
ArgumentNullException

The host parameter is null.

SocketException

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

ObjectDisposedException

The Socket has been closed.

SecurityException

A caller higher in the call stack does not have permission for the requested operation.

ArgumentOutOfRangeException

The port number is not valid.

The asynchronous BeginConnect operation must be completed by calling the EndConnect method. Typically, the method is invoked by the asyncCallback delegate.

This method does not block until the operation completes. To block until the operation completes, use one of the Connect method overloads.

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

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 following code example creates a TcpClient and connects to a remote host.

// Connect asynchronously to the specifed host. 
public static void DoBeginConnect3(string host, int port)
{
    TcpClient t = new TcpClient(AddressFamily.InterNetwork);

    connectDone.Reset();

    Console.WriteLine("Establishing Connection to {0}", 
        host);
    t.BeginConnect(host, port, 
        new AsyncCallback(ConnectCallback), t);

    // Wait here until the callback processes the connection.
    connectDone.WaitOne();

    Console.WriteLine("Connection established");
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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