Begins to asynchronously receive the specified number of bytes of data into the specified location in the data buffer, using the specified SocketAsyncEventArgs.SocketFlags, and stores the endpoint and packet information.
Syntax
Parameters
- e
Returns
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.
Remarks
The Socket.ReceiveMessageFromAsync(SocketAsyncEventArgs) method is used primarily to receive message data on a connectionless socket. The socket's local address must be known. This method can only be used with datagram and raw sockets. The socket must be initialized with the socket type set to SocketType.Dgram or SocketType.Raw before calling this method. This can be done when the socket is constructed using Socket.#ctor(AddressFamily, SocketType, ProtocolType).
The caller must set the SocketAsyncEventArgs.RemoteEndPoint property to the System.Net.IPEndPoint of the remote host from which the data is to be received.
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 Socket.ReceiveMessageFromAsync(SocketAsyncEventArgs) 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 message-oriented sockets, an incoming message is placed into the buffer up to the total size of the buffer. The SocketAsyncEventArgs.Count and SocketAsyncEventArgs.Offset properties determine where in the buffer the data is placed and the amount of data.
The Socket.ReceiveMessageFromAsync(SocketAsyncEventArgs) method automatically sets the SocketOptionName.PacketInformation socket option to true the first time it is called for a given System.Net.Sockets.Socket. However, the System.Net.Sockets.IPPacketInformation object will only be valid for packets which arrive at the local computer after the socket option has been set. If a socket is sent packets between when the socket is bound to a local endpoint (explicitly by the Socket.Bind(System.Net.EndPoint) method or implicitly by one of the Socket.Connect(System.Net.EndPoint), Socket.ConnectAsync(SocketAsyncEventArgs), Socket.SendTo(Byte[], int, int, SocketFlags, System.Net.EndPoint), or Socket.SendToAsync(SocketAsyncEventArgs) methods) and the first call to the Socket.ReceiveMessageFromAsync(SocketAsyncEventArgs) method, calls to Socket.ReceiveMessageFromAsync(SocketAsyncEventArgs) method will result in invalid System.Net.Sockets.IPPacketInformation objects for these packets.
To ensure that all System.Net.Sockets.IPPacketInformation objects are valid, an application should set the SocketOptionName.PacketInformation socket option to true before it is bound to a local endpoint using the Socket.SetSocketOption(SocketOptionLevel, SocketOptionName, bool) method.
An application can examine the resulting System.Net.Sockets.IPPacketInformation objects if it needs to know if the datagram was sent using a unicast, multicast, or broadcast address.
Requirements
Assembly: System (in System.dll)
Assembly Versions: 2.0.0.0, 4.0.0.0