UdpClient.BeginReceive(AsyncCallback, Object) 方法
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
非同步接收遠端主機的資料包。
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 -> IAsyncResultPublic Function BeginReceive (requestCallback As AsyncCallback, state As Object) As IAsyncResult參數
- requestCallback
- AsyncCallback
AsyncCallback 委派，會於作業完成時參考要叫用的方法。
- state
- Object
使用者定義的物件，包含接收作業的相關資訊。 作業完成時會將這個物件傳遞至 requestCallback 委派。
傳回
IAsyncResult 物件，參考非同步接收。
範例
下列程式代碼範例會使用 BeginReceive 以異步方式接收伺服器回應。
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);
}
}
備註
BeginReceive異步操作必須藉由呼叫 EndReceive 方法來完成。 一般而言，委派會叫用 requestCallback 方法。
這個方法不會在作業完成之前封鎖。 若要封鎖直到作業完成為止，請使用 Receive 方法。
如需使用異步程序設計模型的詳細資訊，請參閱 以異步方式呼叫同步方法。
