Receives a datagram from a remote host asynchronously.
(in System.dll)
Visual Basic (Declaration)
<HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading := True)> _
Public Function BeginReceive ( _
requestCallback As AsyncCallback, _
state As Object _
) As IAsyncResult
Dim instance As UdpClient
Dim requestCallback As AsyncCallback
Dim state As Object
Dim returnValue As IAsyncResult
returnValue = instance.BeginReceive(requestCallback, _
state)
[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public IAsyncResult BeginReceive(
AsyncCallback requestCallback,
Object state
)
[HostProtectionAttribute(SecurityAction::LinkDemand, ExternalThreading = true)]
public:
IAsyncResult^ BeginReceive(
AsyncCallback^ requestCallback,
Object^ state
)
public function BeginReceive(
requestCallback : AsyncCallback,
state : Object
) : IAsyncResult
Parameters
- 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 receive operation. This object is passed to the requestCallback delegate when the operation is complete.
The asynchronous BeginReceive operation must be completed by calling the EndReceive 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 the Receive method.
For detailed information about using the asynchronous programming model, see Calling Synchronous Methods Asynchronously.
The following code example uses BeginReceive to asynchronously receive a server response.
public static bool messageReceived = false;
public static void ReceiveCallback(IAsyncResult ar)
{
UdpClient u = (UdpClient)((UdpState)(ar.AsyncState)).u;
IPEndPoint e = (IPEndPoint)((UdpState)(ar.AsyncState)).e;
Byte[] receiveBytes = u.EndReceive(ar, ref e);
string receiveString = Encoding.ASCII.GetString(receiveBytes);
Console.WriteLine("Received: {0}", receiveString);
messageReceived = true;
}
public static void ReceiveMessages()
{
// Receive a message and write it to the console.
IPEndPoint e = new IPEndPoint(IPAddress.Any, listenPort);
UdpClient u = new UdpClient(e);
UdpState s = new UdpState();
s.e = e;
s.u = u;
Console.WriteLine("listening for messages");
u.BeginReceive(new AsyncCallback(ReceiveCallback), s);
// Do some work while we wait for a message. For this example,
// we'll just sleep
while (!messageReceived)
{
Thread.Sleep(100);
}
}
public:
static bool isMessageReceived;
static void ReceiveCallback(IAsyncResult^ asyncResult)
{
UdpClient^ udpClient =
((UdpState)(asyncResult->AsyncState)).udpClient;
IPEndPoint^ ipEndPoint =
((UdpState)(asyncResult->AsyncState)).ipEndPoint;
array<Byte>^ receiveBytes =
udpClient->EndReceive(asyncResult, ipEndPoint);
String^ receiveString =
Encoding::ASCII->GetString(receiveBytes);
Console::WriteLine("Received: {0}", receiveString);
isMessageReceived = true;
}
static void ReceiveMessages()
{
// Receive a message and write it to the console.
IPEndPoint^ ipEndPoint = gcnew IPEndPoint(IPAddress::Any, listenPort);
UdpClient^ udpClient = gcnew UdpClient(ipEndPoint);
UdpState^ udpState = gcnew UdpState();
udpState->ipEndPoint = ipEndPoint;
udpState->udpClient = udpClient;
Console::WriteLine("listening for messages");
udpClient->BeginReceive(gcnew AsyncCallback(ReceiveCallback),
udpState);
// Do some work while we wait for a message. For this example,
// we'll just sleep
while (!isMessageReceived)
{
Thread::Sleep(100);
}
}
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
Reference