Socket.BeginConnect Method (String, Int32, AsyncCallback, Object) (System.Net.Sockets)

BeginConnect Method (String, Int32,...

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

Socket..::.BeginConnect Method (String, Int32, AsyncCallback, Object)

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

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

Syntax

Visual Basic (Declaration)

<HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading := True)> _
Public Function BeginConnect ( _
    host As String, _
    port As Integer, _
    requestCallback As AsyncCallback, _
    state As Object _
) As IAsyncResult

Visual Basic (Usage)

Dim instance As Socket
Dim host As String
Dim port As Integer
Dim requestCallback As AsyncCallback
Dim state As Object
Dim returnValue As IAsyncResult

returnValue = instance.BeginConnect(host, _
    port, requestCallback, state)

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

Visual C++

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

JScript

public function BeginConnect(
    host : String, 
    port : int, 
    requestCallback : AsyncCallback, 
    state : Object
) : IAsyncResult

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 connect 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 that references the asynchronous connection.

Exceptions

Exception	Condition
ArgumentNullException	host is nullNothingnullptra null reference (Nothing in Visual Basic).
ObjectDisposedException	The Socket has been closed.
NotSupportedException	This method is valid for sockets in the InterNetwork or InterNetworkV6 families.
ArgumentOutOfRangeException	The port number is not valid.
InvalidOperationException	The Socket is Listening.

Remarks

Note:
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.

Note:

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

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

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

Note:
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.

Note:
If this socket has previously been disconnected, then BeginConnect must be called on a thread that will not exit until the operation is complete. This is a limitation of the underlying provider. Also the EndPoint that is used must be different.

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

Note:
The execution context (the security context, the impersonated user, and the calling context) is cached for the asynchronous Socket methods. After the first use of a particular context (a specific asynchronous Socket method, a specific Socket instance, and a specific callback), subsequent uses of that context will see a performance improvement.

Examples

The following code example initiates an asynchronous connection attempt.

public static ManualResetEvent allDone = 
    new ManualResetEvent(false);

// handles the completion of the prior asynchronous 
// connect call. the socket is passed via the objectState 
// paramater of BeginConnect().
public static void ConnectCallback1(IAsyncResult ar)
{
    allDone.Set();
    Socket s = (Socket) ar.AsyncState;
    s.EndConnect(ar);
}

Visual C++

static ManualResetEvent^ allDone = gcnew ManualResetEvent( false );

// handles the completion of the prior asynchronous 
// connect call. the socket is passed via the objectState 
// paramater of BeginConnect().
static void ConnectCallback1( IAsyncResult^ ar )
{
   allDone->Set();
   Socket^ s = dynamic_cast<Socket^>(ar->AsyncState);
   s->EndConnect( ar );
}

CPP_OLD

public:
    static ManualResetEvent* allDone = 
        new ManualResetEvent(false);

    // handles the completion of the prior asynchronous 
    // connect call. the socket is passed via the objectState 
    // paramater of BeginConnect().
    static void ConnectCallback1(IAsyncResult* ar)
    {
        allDone->Set();
        Socket* s = dynamic_cast<Socket*> (ar->AsyncState);
        s->EndConnect(ar);
    }

// Asynchronous connect using host name (resolved by the 
// BeginConnect call.)
public static void BeginConnect3(string host, int port)
{
    Socket s = new Socket(AddressFamily.InterNetwork,
        SocketType.Stream,
        ProtocolType.Tcp);

    allDone.Reset();

    Console.WriteLine("Establishing Connection to {0}", 
        host);
    s.BeginConnect(host, port, 
        new AsyncCallback(ConnectCallback1), s);

    // wait here until the connect finishes.  The callback 
    // sets allDone.
    allDone.WaitOne();

    Console.WriteLine("Connection established");
}

Visual C++

// Asynchronous connect using host name (resolved by the 
// BeginConnect call.)
static void BeginConnect3( String^ host, int port )
{
   Socket^ s = gcnew Socket( AddressFamily::InterNetwork,SocketType::Stream,ProtocolType::Tcp );
   allDone->Reset();
   Console::WriteLine( "Establishing Connection to {0}", host );
   s->BeginConnect( host, port, gcnew AsyncCallback( ConnectCallback1 ), s );

   // wait here until the connect finishes.  The callback 
   // sets allDone.
   allDone->WaitOne();
   Console::WriteLine( "Connection established" );
}

CPP_OLD

// Asynchronous connect using host name (resolved by the 
// BeginConnect call.)
static void BeginConnect3(String* host, int port)
{
    Socket* s = new Socket(AddressFamily::InterNetwork,
        SocketType::Stream,
        ProtocolType::Tcp);

    allDone->Reset();

    Console::WriteLine(S"Establishing Connection to {0}", 
        host);
    s->BeginConnect(host, port, 
        new AsyncCallback(ConnectCallback1), s);

    // wait here until the connect finishes.  The callback 
    // sets allDone.
    allDone->WaitOne();

    Console::WriteLine(S"Connection established");
}

Platforms

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.

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0

Reference

Socket Class

Socket Members

BeginConnect Overload

System.Net.Sockets Namespace

Other Resources

Callback Sample

Asynchronous Client Socket Example

Asynchronous Server Socket Example