Socket::BeginConnect Method (array<IPAddress^>^, Int32, AsyncCallback^, Object^)

 

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

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

public:
[HostProtectionAttribute(SecurityAction::LinkDemand, ExternalThreading = true)]
IAsyncResult^ BeginConnect(
	array<IPAddress^>^ addresses,
	int port,
	AsyncCallback^ requestCallback,
	Object^ state
)

Parameters

addresses
Type: array<System.Net::IPAddress^>^

At least one IPAddress, designating 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 connections.

Exception Condition
ArgumentNullException

addresses 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.

NotSupportedException

This method is valid for sockets that use InterNetwork or InterNetworkV6.

ArgumentOutOfRangeException

The port number is not valid.

ArgumentException

The length of address is zero.

InvalidOperationException

The Socket is Listening.

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.

To cancel a pending call to the BeginConnect method, close the Socket. When the Close method is called while an asynchronous operation is in progress, the callback provided to the BeginConnect method is called. A subsequent call to the EndConnect method will throw an ObjectDisposedException to indicate that the operation has been cancelled.

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

System_CAPS_noteNote

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.

System_CAPS_noteNote

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.

System_CAPS_noteNote

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

System_CAPS_noteNote

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.

The following code example initiates an asynchronous connection attempt.

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 );
}


// Asynchronous connect, using DNS.ResolveToAddresses
static void BeginConnect2( String^ host, int port )
{
   array<IPAddress^>^IPs = Dns::GetHostAddresses( host );
   Socket^ s = gcnew Socket( AddressFamily::InterNetwork,SocketType::Stream,ProtocolType::Tcp );
   allDone->Reset();
   Console::WriteLine( "Establishing Connection to {0}", host );
   s->BeginConnect( IPs, port, gcnew AsyncCallback( ConnectCallback1 ), s );

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


.NET Framework
Available since 2.0
Return to top
Show: