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Socket.ReceiveAsync Method

Begins an asynchronous request to receive data from a connected Socket object.

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

public bool ReceiveAsync(
	SocketAsyncEventArgs e


Type: System.Net.Sockets.SocketAsyncEventArgs

The System.Net.Sockets.SocketAsyncEventArgs object to use for this asynchronous socket operation.

Return Value

Type: System.Boolean
Returns true if the I/O operation is pending. The SocketAsyncEventArgs.Completed event on the e parameter will be raised upon completion of the operation.
Returns false if the I/O operation completed synchronously. In this case, The SocketAsyncEventArgs.Completed event on the e parameter will not be raised and the e object passed as a parameter may be examined immediately after the method call returns to retrieve the result of the operation.


An argument was invalid. The SocketAsyncEventArgs.Buffer or SocketAsyncEventArgs.BufferList properties on the e parameter must reference valid buffers. One or the other of these properties may be set, but not both at the same time.


A socket operation was already in progress using the System.Net.Sockets.SocketAsyncEventArgs object specified in the e parameter.


Windows XP or later is required for this method.


The Socket has been closed.


An error occurred when attempting to access the socket. See the Remarks section for more information.

The ReceiveAsync method is used on connected sockets or bound connectionless sockets and is used to read incoming data. The socket's local address must be known.

For bound connectionless sockets, this function restricts the addresses from which received messages are accepted. The function only returns messages from the remote address specified in the connection. Messages from other addresses are silently discarded.

The SocketAsyncEventArgs.SocketFlags property on the e parameter provides the Window Sockets service provider with additional information about the read request. For more information about how to use this parameter, see System.Net.Sockets.SocketFlags.

The following properties and events on the System.Net.Sockets.SocketAsyncEventArgs object are required to successfully call this method:

The caller may set the SocketAsyncEventArgs.UserToken property to any user state object desired before calling the ReceiveAsync method, so that the information will be retrievable in the callback method. If the callback needs more information than a single object, a small class can be created to hold the other required state information as members.

For byte stream-style sockets, incoming data is placed into the buffer until the buffer is filled, the connection is closed, or the internally buffered data is exhausted.

For message-oriented sockets, an incoming message is placed into the buffer up to the total size of the buffer associated with the e parameter. If the message is larger than the buffer, the buffer is filled with the first part of the message.

For connection-oriented sockets, the ReceiveAsync method can indicate the graceful termination of the virtual circuit in one of two ways that depend on whether the socket is byte stream or message oriented. For byte streams, zero bytes having been read indicates graceful closure and that no more bytes will ever be read. For message-oriented sockets, where a zero byte message is often allowable, a SocketException with the SocketAsyncEventArgs.SocketError set to the native Winsock WSAEDISCON error code (10101) is used to indicate graceful closure. In any case, a SocketException with the SocketAsyncEventArgs.SocketError set to the native Winsock WSAECONNRESET error code (10054) indicates an abortive close has occurred.

Problems may occur if the SetBuffer method is called from a thread while the M:System.Net.Sockets.Socket.ReceiveAsync(System.Net.Sockets.SocketAsyncEventArgs)ReceiveAsync method is called from a different thread. These problems can be prevented by putting locks around these methods to keep the methods from being called at the same time.

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

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

.NET Framework

Supported in: 3.5 SP1, 3.0 SP1, 2.0 SP1