NetworkStream.EndRead(IAsyncResult) Method


Handles the end of an asynchronous read.

 override int EndRead(IAsyncResult ^ asyncResult);
public override int EndRead (IAsyncResult asyncResult);
override this.EndRead : IAsyncResult -> int
Public Overrides Function EndRead (asyncResult As IAsyncResult) As Integer



An IAsyncResult that represents an asynchronous call.


The number of bytes read from the NetworkStream.


The asyncResult parameter is null.

The underlying Socket is closed.


An error occurred when accessing the socket.


In the following code example, myReadCallback is provided to BeginRead as the callback method. EndRead is implemented in myReadCallback to complete the asynchronous read call started by BeginRead.

// Example of EndRead, DataAvailable and BeginRead.
static void myReadCallBack( IAsyncResult^ ar )
   NetworkStream^ myNetworkStream = safe_cast<NetworkStream^>(ar->AsyncState);
   array<Byte>^myReadBuffer = gcnew array<Byte>(1024);
   String^ myCompleteMessage = "";
   int numberOfBytesRead;
   numberOfBytesRead = myNetworkStream->EndRead( ar );
   myCompleteMessage = String::Concat( myCompleteMessage, Encoding::ASCII->GetString( myReadBuffer, 0, numberOfBytesRead ) );
   // message received may be larger than buffer size so loop through until you have it all.
   while ( myNetworkStream->DataAvailable )
      AsyncCallback^ pasync = gcnew AsyncCallback( &myReadCallBack );
      myNetworkStream->BeginRead( myReadBuffer, 0, myReadBuffer->Length, pasync, myNetworkStream );

   // Print out the received message to the console.
   Console::WriteLine( "You received the following message : {0}", myCompleteMessage );
// Example of EndRead, DataAvailable and BeginRead.

public static void myReadCallBack(IAsyncResult ar ){

    NetworkStream myNetworkStream = (NetworkStream)ar.AsyncState;
    byte[] myReadBuffer = new byte[1024];
    String myCompleteMessage = "";
    int numberOfBytesRead;

    numberOfBytesRead = myNetworkStream.EndRead(ar);
    myCompleteMessage = 
        String.Concat(myCompleteMessage, Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead));    
    // message received may be larger than buffer size so loop through until you have it all.
        myNetworkStream.BeginRead(myReadBuffer, 0, myReadBuffer.Length, 
                                                   new AsyncCallback(NetworkStream_ASync_Send_Receive.myReadCallBack), 


    // Print out the received message to the console.
    Console.WriteLine("You received the following message : " +

' Example of EndRead, DataAvailable and BeginRead.
Public Shared Sub myReadCallBack(ar As IAsyncResult)
   Dim myNetworkStream As NetworkStream = CType(ar.AsyncState, NetworkStream)
   Dim myReadBuffer(1024) As Byte
   Dim myCompleteMessage As [String] = ""
   Dim numberOfBytesRead As Integer
   numberOfBytesRead = myNetworkStream.EndRead(ar)
   myCompleteMessage = [String].Concat(myCompleteMessage, Encoding.ASCII.GetString(myReadBuffer, 0, numberOfBytesRead))
   ' message received may be larger than buffer size so loop through until you have it all.
   While myNetworkStream.DataAvailable
      myNetworkStream.BeginRead(myReadBuffer, 0, myReadBuffer.Length, New AsyncCallback(AddressOf NetworkStream_ASync_Send_Receive.myReadCallBack), myNetworkStream)
   End While
   ' Print out the received message to the console.
   Console.WriteLine(("You received the following message : " + myCompleteMessage))
End Sub


The EndRead method completes the asynchronous read operation started in the BeginRead method.

Before calling BeginRead, 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 BeginRead returns. The callback method must accept the IAsyncResult returned from the BeginRead method as a parameter.

Within the callback method, call the AsyncState property of the IAsyncResult to obtain the state object passed to the BeginRead method. Extract the receiving NetworkStream from this state object. After obtaining the NetworkStream, call the EndRead method to successfully complete the read operation and return the number of bytes read.

The EndRead method blocks until data is available. The EndRead method reads as much data as is available up to the number of bytes specified in the size parameter of the BeginRead method. If the remote host shuts down the Socket connection and all available data has been received, the EndRead method completes immediately and returns zero bytes.

To obtain the received data, call the AsyncState property of the IAsyncResult, and extract the buffer contained in the resulting state object.


If you receive an IOException, check the InnerException property to determine if it was caused by a SocketException. If so, use the ErrorCode property to obtain the specific error code and refer to the Windows Sockets version 2 API error code documentation for a detailed description of the error.

Applies to

See also