This documentation is archived and is not being maintained.

Socket.EndSendTo Method

Ends a pending asynchronous send to a specific location.

[Visual Basic]
Public Function EndSendTo( _
   ByVal asyncResult As IAsyncResult _
) As Integer
public int EndSendTo(
 IAsyncResult asyncResult
public: int EndSendTo(
 IAsyncResult* asyncResult
public function EndSendTo(
   asyncResult : IAsyncResult
) : int;


An IAsyncResult that stores state information and any user defined data for this asynchronous operation.

Return Value

If successful, the number of bytes sent; otherwise, an invalid Socket error.


Exception Type Condition
ArgumentNullException asyncResult is a null reference (Nothing in Visual Basic).
ArgumentException asyncResult was not returned by a call to the BeginSendTo method.
InvalidOperationException EndSendTo was previously called for the asynchronous read.
SocketException An error occurred when attempting to access the socket. See the Remarks section for more information.
ObjectDisposedException The Socket has been closed.


EndSendTo completes the asynchronous send operation started in BeginSendTo.

Before calling BeginSendTo, you need to create a callback method that implements the AsyncCallback delegate. This callback method executes in a separate thread and is called by the system after BeginReceive returns. The callback method must accept the IAsyncResult returned by the BeginSendTo method as a parameter.

Within the callback method, call the AsyncState method of the IAsyncResult parameter to obtain the sending Socket. After obtaining the Socket, you can call the EndSendTo method to successfully complete the send operation and return the number of bytes sent.

If you are using a connectionless protocol, EndSendTo will block until the datagram is sent. If you are using a connection-oriented protocol, EndSendTo will block until the requested number of bytes are sent. There is no guarantee that the data you send will appear on the network immediately. To increase network efficiency, the underlying system may delay transmission until a significant amount of outgoing data is collected. A successful completion of the BeginSendTo method means that the underlying system has had room to buffer your data for a network send. If it is important to your application to send every byte to the remote host immediately, you can use SetSocketOption to enable SocketOptionName.NoDelay. For more information about buffering for network efficiency, refer to the Nagle algorithm in MSDN.

Note   If you receive a SocketException, use SocketException.ErrorCode to obtain the specific error code. Once you have obtained this code, you can refer to the Windows Socket Version 2 API error code documentation in MSDN for a detailed description of the error.


[Visual Basic, C#, C++] The following example ends an asynchronous send to a specific location.

[Visual Basic] 
Dim so As StateObject = CType(ar.AsyncState, StateObject)
Dim s As Socket = so.workSocket

Dim send As Integer = s.EndSendTo(ar)

Console.WriteLine(("The size of the message sent was :" + send.ToString()))

   End Sub 'SendTo_Callback

StateObject so = (StateObject) ar.AsyncState;
Socket s = so.workSocket;

int send = s.EndSendTo(ar);

   Console.WriteLine("The size of the message sent was :" + send.ToString());


StateObject* so = __try_cast<StateObject*>(ar->AsyncState);
Socket* s = so->workSocket;

int send = s->EndSendTo(ar);

Console::WriteLine(S"The size of the message sent was : {0}", __box(send));


[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.


Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard

See Also

Socket Class | Socket Members | System.Net.Sockets Namespace | Including Asynchronous Calls