SslStream.BeginRead Method

Begins an asynchronous read operation that reads data from the stream and stores it in the specified array.

Namespace:  System.Net.Security
Assembly:  System (in System.dll)

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public override IAsyncResult BeginRead(
	byte[] buffer,
	int offset,
	int count,
	AsyncCallback asyncCallback,
	Object asyncState
)

Parameters

buffer
Type: 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.

ExceptionCondition
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.

NoteNote

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

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 = new StringBuilder();
static byte [] buffer = new byte[2048];
static void WriteCallback(IAsyncResult ar)
{
    SslStream stream = (SslStream) ar.AsyncState;
    try 
    {
        Console.WriteLine("Writing data to the server.");
        stream.EndWrite(ar);
        // Asynchronously read a message from the server.
        stream.BeginRead(buffer, 0, buffer.Length, 
            new 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 = (SslStream) ar.AsyncState;
    int byteCount = -1;
    try 
    {
        Console.WriteLine("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();
        char[] chars = new 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("<EOF>") == -1 && byteCount != 0)
        {
            // We are not finished reading. 
            // Asynchronously read more message data from  the server.
            stream.BeginRead(buffer, 0, buffer.Length, 
                new AsyncCallback(ReadCallback),
                stream);
        } 
        else
        {
            Console.WriteLine("Message from the server: {0}", readData.ToString());
        }
    }
    catch (Exception readException)
    {
        e = readException;
        complete = true;
        return;
    }
    complete = true;
}

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

Was this page helpful?
(1500 characters remaining)
Thank you for your feedback
Show:
© 2014 Microsoft