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Socket.BeginReceive Method (Byte[], Int32, Int32, SocketFlags, AsyncCallback, Object)

Begins to asynchronously receive data from a connected Socket.

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

public IAsyncResult BeginReceive (
	byte[] buffer,
	int offset,
	int size,
	SocketFlags socketFlags,
	AsyncCallback callback,
	Object state
)
public IAsyncResult BeginReceive (
	byte[] buffer, 
	int offset, 
	int size, 
	SocketFlags socketFlags, 
	AsyncCallback callback, 
	Object state
)
public function BeginReceive (
	buffer : byte[], 
	offset : int, 
	size : int, 
	socketFlags : SocketFlags, 
	callback : AsyncCallback, 
	state : Object
) : IAsyncResult

Parameters

buffer

An array of type Byte that is the storage location for the received data.

offset

The zero-based position in the buffer parameter at which to store the received data.

size

The number of bytes to receive.

socketFlags

A bitwise combination of the SocketFlags values.

callback

An AsyncCallback delegate that references the method to invoke when the operation is complete.

state

A user-defined object that contains information about the receive operation. This object is passed to the EndReceive delegate when the operation is complete.

Return Value

An IAsyncResult that references the asynchronous read.

Exception typeCondition

ArgumentNullException

buffer is a null reference (Nothing in Visual Basic).

SocketException

An error occurred when attempting to access the socket. See the Remarks section for more information.

ObjectDisposedException

Socket has been closed.

ArgumentOutOfRangeException

offset is less than 0.

-or-

offset is greater than the length of buffer.

-or-

size is less than 0.

-or-

size is greater than the length of buffer minus the value of the offset parameter.

The asynchronous BeginReceive operation must be completed by calling the EndReceive method. Typically, the method is invoked by the callback delegate.

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

To cancel a pending BeginReceive, call the Close method.

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

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.

NoteNote

All I/O initiated by a given thread is canceled when that thread exits. A pending asynchronous operation can fail if the thread exits before the operation completes.

NoteNote

state is an instantiation of a user-defined class.

NoteNote

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

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 begins to asynchronously receive data from a connected Socket.

public class StateObject{
     public Socket workSocket = null;
     public const int BUFFER_SIZE = 1024;
     public byte[] buffer = new byte[BUFFER_SIZE];
     public StringBuilder sb = new StringBuilder();
}

public static void Listen_Callback(IAsyncResult ar){
     allDone.Set();
     Socket s = (Socket) ar.AsyncState;
     Socket s2 = s.EndAccept(ar);
     StateObject so2 = new StateObject();
     so2.workSocket = s2;
     s2.BeginReceive(so2.buffer, 0, StateObject.BUFFER_SIZE,0,
	                       new AsyncCallback(Async_Send_Receive.Read_Callback), so2);	
}

allDone.Set();
Socket s = (Socket)ar.get_AsyncState();
Socket s2 = s.EndAccept(ar);
StateObject so2 = new StateObject();
so2.workSocket = s2;
s2.BeginReceive(so2.buffer, 0, StateObject.BUFFER_SIZE,
    (SocketFlags)0, new AsyncCallback(Async_Send_Receive.Read_Callback),
    so2);

public static void Read_Callback(IAsyncResult ar){
	StateObject so = (StateObject) ar.AsyncState;
	Socket s = so.workSocket;

	int read = s.EndReceive(ar);

	if (read > 0) {
            so.sb.Append(Encoding.ASCII.GetString(so.buffer, 0, read));
            s.BeginReceive(so.buffer, 0, StateObject.BUFFER_SIZE, 0, 
            	                     new AsyncCallback(Async_Send_Receive.Read_Callback), so);
	}
	else{
	     if (so.sb.Length > 1) {
	          //All of the data has been read, so displays it to the console
	          string strContent;
	          strContent = so.sb.ToString();
	          Console.WriteLine(String.Format("Read {0} byte from socket" + 
	          	               "data = {1} ", strContent.Length, strContent));
	     }
	     s.Close();
	}
}

StateObject so = (StateObject)ar.get_AsyncState();
Socket s = so.workSocket;
int read = s.EndReceive(ar);

if (read > 0) {
    so.sb.Append(Encoding.get_ASCII().GetString(so.buffer, 0, read));
    s.BeginReceive(so.buffer, 0, StateObject.BUFFER_SIZE,
        (SocketFlags)0, new AsyncCallback(Async_Send_Receive.
        Read_Callback), so);
}
else {
    if (so.sb.get_Length() > 1) {
        //All of the data has been read, so displays it to the console
        String strContent;
        strContent = so.sb.ToString();
        Console.WriteLine(String.Format("Read {0} byte from socket"
            + "data = {1} ", (Int32)strContent.get_Length(), 
            strContent));
    }
    s.Close();
}

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0
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