SslStream::BeginRead Method (array<Byte>^, Int32, Int32, AsyncCallback^, Object^)
Begins an asynchronous read operation that reads data from the stream and stores it in the specified array.
Assembly: System (in System.dll)
public: [HostProtectionAttribute(SecurityAction::LinkDemand, ExternalThreading = true)] virtual IAsyncResult^ BeginRead( array<unsigned char>^ buffer, int offset, int count, AsyncCallback^ asyncCallback, Object^ asyncState ) override
Parameters
- buffer
-
Type:
array<System::Byte>^
A Byte array that receives the bytes read from the stream.
- offset
-
Type:
System::Int32
The zero-based location in buffer at which to begin storing the data read from this stream.
- count
-
Type:
System::Int32
The maximum number of bytes to read from the stream.
- asyncCallback
-
Type:
System::AsyncCallback^
An AsyncCallback delegate that references the method to invoke when the read operation is complete.
- asyncState
-
Type:
System::Object^
A user-defined object that contains information about the read operation. This object is passed to the asyncCallback delegate when the operation completes.
Return Value
Type: System::IAsyncResult^An IAsyncResult object that indicates the status of the asynchronous operation.
| Exception | Condition |
|---|---|
| ArgumentNullException | buffer is null. |
| ArgumentException | offset<0. -or- offset > the length of buffer. -or- offset + count > the length of buffer. |
| IOException | The read operation failed. -or- Encryption is in use, but the data could not be decrypted. |
| NotSupportedException | There is already a read operation in progress. |
| ObjectDisposedException | This object has been closed. |
| InvalidOperationException | Authentication has not occurred. |
If encryption and or signing are enabled, the read operation reads the data from the underlying stream, checks the integrity of the data, and/or decrypts it. The asynchronous read operation must be completed by calling the EndRead method. Typically, the method is invoked by the asyncCallback delegate.
This method does not block while the operation completes. To block until the operation completes, use the Read method.
For detailed information about using the asynchronous programming model, see Calling Synchronous Methods Asynchronously
The SslStream class does not support multiple simultaneous read operations.
You cannot call this method until you have successfully authenticated. To authenticate call one of the AuthenticateAsClient, or BeginAuthenticateAsClient, AuthenticateAsServer, BeginAuthenticateAsServer methods.
The following code example demonstrates starting an asynchronous read operation.
// readData and buffer holds the data read from the server. // They is used by the ReadCallback method. static StringBuilder^ readData = gcnew StringBuilder; static array<Byte>^buffer = gcnew array<Byte>(2048);
static void WriteCallback( IAsyncResult^ ar ) { SslStream^ stream = dynamic_cast<SslStream^>(ar->AsyncState); try { Console::WriteLine( L"Writing data to the server." ); stream->EndWrite( ar ); // Asynchronously read a message from the server. stream->BeginRead( buffer, 0, buffer->Length, gcnew AsyncCallback( ReadCallback ), stream ); } catch ( Exception^ writeException ) { e = writeException; complete = true; return; } }
The following method is called when the read completes.
static void ReadCallback( IAsyncResult^ ar ) { // Read the message sent by the server. // The end of the message is signaled using the // "<EOF>" marker. SslStream^ stream = dynamic_cast<SslStream^>(ar->AsyncState); int byteCount = -1; try { Console::WriteLine( L"Reading data from the server." ); byteCount = stream->EndRead( ar ); // Use Decoder class to convert from bytes to UTF8 // in case a character spans two buffers. Decoder^ decoder = Encoding::UTF8->GetDecoder(); array<Char>^chars = gcnew array<Char>(decoder->GetCharCount( buffer, 0, byteCount )); decoder->GetChars( buffer, 0, byteCount, chars, 0 ); readData->Append( chars ); // Check for EOF or an empty message. if ( readData->ToString()->IndexOf( L"<EOF>" ) == -1 && byteCount != 0 ) { // We are not finished reading. // Asynchronously read more message data from the server. stream->BeginRead( buffer, 0, buffer->Length, gcnew AsyncCallback( ReadCallback ), stream ); } else { Console::WriteLine( L"Message from the server: {0}", readData ); } } catch ( Exception^ readException ) { e = readException; complete = true; return; } complete = true; }
Available since 2.0