UdpClient.BeginReceive(AsyncCallback, Object) Method
Definition
Important
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Receives a datagram from a remote host asynchronously.
public:
IAsyncResult ^ BeginReceive(AsyncCallback ^ requestCallback, System::Object ^ state);
public IAsyncResult BeginReceive (AsyncCallback? requestCallback, object? state);
public IAsyncResult BeginReceive (AsyncCallback requestCallback, object state);
member this.BeginReceive : AsyncCallback * obj -> IAsyncResult
Public Function BeginReceive (requestCallback As AsyncCallback, state As Object) As IAsyncResult
Parameters
- requestCallback
- AsyncCallback
An AsyncCallback delegate that references the method to invoke when the operation is complete.
- state
- 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.
Returns
An IAsyncResult object that references the asynchronous receive.
Examples
The following code example uses BeginReceive to asynchronously receive a server response.
private:
static int listenPort = 13000;
public:
value struct UdpState
{
public:
UdpClient^ udpClient;
IPEndPoint^ ipEndPoint;
};
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);
}
}
public struct UdpState
{
public UdpClient u;
public IPEndPoint e;
}
public static bool messageReceived = false;
public static void ReceiveCallback(IAsyncResult ar)
{
UdpClient u = ((UdpState)(ar.AsyncState)).u;
IPEndPoint e = ((UdpState)(ar.AsyncState)).e;
byte[] receiveBytes = u.EndReceive(ar, ref e);
string receiveString = Encoding.ASCII.GetString(receiveBytes);
Console.WriteLine($"Received: {receiveString}");
messageReceived = true;
}
public static void ReceiveMessages()
{
// Receive a message and write it to the console.
IPEndPoint e = new IPEndPoint(IPAddress.Any, s_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);
}
}
Remarks
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.
Applies to
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