The EndRead method completes the asynchronous read operation started in the
BeginRead <frlrfsystemnetsocketsnetworkstreamclassbeginreadtopic.htm>
method.
Before calling BeginRead, you need to create a callback method that
implements the AsyncCallback <frlrfsystemasynccallbackclasstopic.htm>
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 <frlrfsystemiasyncresultclasstopic.htm> returned from the
BeginRead method as a parameter.
Within the callback method, call the AsyncState
<frlrfsystemiasyncresultclassasyncstatetopic.htm> method of the IAsyncResult
to obtain the state object passed to the BeginRead method. Extract the
receiving NetworkStream <frlrfsystemnetsocketsnetworkstreamclasstopic.htm>
from this state object. After obtaining the NetworkStream, you can call the
EndRead method to successfully complete the read operation and return the
number of bytes read.
The EndRead method will block until data is available. The EndRead method
will read 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 <frlrfsystemnetsocketssocketclasstopic.htm> connection and all
available data has been received, the EndRead method will complete
immediately and return zero bytes.
To obtain the received data, call the AsyncState method of the IAsyncResult,
and extract the buffer contained in the resulting state object.
Note If you receive a IOException <frlrfsystemioioexceptionclasstopic.htm>
check the InnerException <frlrfsystemexceptionclassinnerexceptiontopic.htm>
property to determine if it was caused by a SocketException
<frlrfsystemnetsocketssocketexceptionclasstopic.htm>. If so, use ErrorCode
<frlrfsystemnetsocketssocketexceptionclasserrorcodetopic.htm> 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.
Example
[Visual Basic, C#, C++] In the following example, myReadCallback is provided
to BeginRead <frlrfsystemnetsocketsnetworkstreamclassbeginreadtopic.htm> as
the callback method. EndRead is implemented in myReadCallback to complete
the asynchronous read call started by BeginRead.
[Visual Basic]
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 'myReadCallBack
'Entry point which delegates to C-style main Private Function
Public Overloads Shared Sub Main()
Main(System.Environment.GetCommandLineArgs())
End Sub
[C#]
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.
while(myNetworkStream.DataAvailable){
myNetworkStream.BeginRead(myReadBuffer, 0, myReadBuffer.Length,
new
AsyncCallback(NetworkStream_ASync_Send_Receive.myReadCallBack),
myNetworkStream);
}
// Print out the received message to the console.
Console.WriteLine("You received the following message : " +
myCompleteMessage);
}
[C++]
static void myReadCallBack(IAsyncResult* ar) {
NetworkStream* myNetworkStream =
__try_cast<NetworkStream*>(ar->AsyncState);
Byte myReadBuffer[] = new Byte[1024];
String* myCompleteMessage = S"";
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 = new AsyncCallback(0, &myReadCallBack);
myNetworkStream->BeginRead(myReadBuffer, 0, myReadBuffer->Length,
pasync,
myNetworkStream);
}
// Print out the received message to the console.
Console::WriteLine(S"You received the following message : {0}",
myCompleteMessage);
}
[JScript] No example is available for JScript. To view a Visual Basic, C#,
or C++ example, click the Language Filter button in the upper-left corner of
the page.
