UdpClient::BeginSend Method (array<Byte>^, Int32, AsyncCallback^, Object^)

 

Sends a datagram to a remote host asynchronously. The destination was specified previously by a call to Connect.

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

public:
[HostProtectionAttribute(SecurityAction::LinkDemand, ExternalThreading = true)]
IAsyncResult^ BeginSend(
	array<unsigned char>^ datagram,
	int bytes,
	AsyncCallback^ requestCallback,
	Object^ state
)

Parameters

datagram
Type: array<System::Byte>^

A Byte array that contains the data to be sent.

bytes
Type: System::Int32

The number of bytes to send.

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 send 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 send.

The asynchronous BeginSend operation must be completed by calling the EndSend method. Typically, the method is invoked by the requestCallback delegate.

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

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

The following code example uses BeginSend to asynchronously send a server request.

public:
    static bool isMessageSent;

    static void SendCallback(IAsyncResult^ asyncResult)
    {
        UdpClient^ udpClient = (UdpClient^)asyncResult->AsyncState;

        Console::WriteLine("number of bytes sent: {0}",
            udpClient->EndSend(asyncResult));
        isMessageSent = true;
    }
public:
    static void SendMessage1(String^ server, String^ message)
    {
        // create the udp socket
        UdpClient^ udpClient = gcnew UdpClient();

        udpClient->Connect(server, listenPort);
        array<Byte>^ sendBytes = Encoding::ASCII->GetBytes(message);

        // send the message
        // the destination is defined by the call to .Connect()
        udpClient->BeginSend(sendBytes, sendBytes->Length,
            gcnew AsyncCallback(SendCallback), udpClient);

        // Do some work while we wait for the send to complete. For
        // this example, we'll just sleep
        while (!isMessageSent)
        {
            Thread::Sleep(100);
        }
    }

.NET Framework
Available since 2.0
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