System.Net.Sockets.SocketAsyncEventArgs.InnerStartOperationReceiveMessageFrom C# (CSharp) Method

        private void InnerStartOperationReceiveMessageFrom()
        {
            // WSARecvMsg uses a WSAMsg descriptor.
            // The WSAMsg buffer is pinned with a GCHandle to avoid complicating the use of Overlapped.
            // WSAMsg contains a pointer to a sockaddr.  
            // The sockaddr is pinned with a GCHandle to avoid complicating the use of Overlapped.
            // WSAMsg contains a pointer to a WSABuffer array describing data buffers.
            // WSAMsg also contains a single WSABuffer describing a control buffer.
            PinSocketAddressBuffer();

            // Create and pin a WSAMessageBuffer if none already.
            if (_wsaMessageBuffer == null)
            {
                _wsaMessageBuffer = new byte[s_wsaMsgSize];
                _wsaMessageBufferGCHandle = GCHandle.Alloc(_wsaMessageBuffer, GCHandleType.Pinned);
                _ptrWSAMessageBuffer = Marshal.UnsafeAddrOfPinnedArrayElement(_wsaMessageBuffer, 0);
            }

            // Create and pin an appropriately sized control buffer if none already
            IPAddress ipAddress = (_socketAddress.Family == AddressFamily.InterNetworkV6 ? _socketAddress.GetIPAddress() : null);
            bool ipv4 = (_currentSocket.AddressFamily == AddressFamily.InterNetwork || (ipAddress != null && ipAddress.IsIPv4MappedToIPv6)); // DualMode
            bool ipv6 = _currentSocket.AddressFamily == AddressFamily.InterNetworkV6;

            if (ipv4 && (_controlBuffer == null || _controlBuffer.Length != s_controlDataSize))
            {
                if (_controlBufferGCHandle.IsAllocated)
                {
                    _controlBufferGCHandle.Free();
                }
                _controlBuffer = new byte[s_controlDataSize];
            }
            else if (ipv6 && (_controlBuffer == null || _controlBuffer.Length != s_controlDataIPv6Size))
            {
                if (_controlBufferGCHandle.IsAllocated)
                {
                    _controlBufferGCHandle.Free();
                }
                _controlBuffer = new byte[s_controlDataIPv6Size];
            }
            if (!_controlBufferGCHandle.IsAllocated)
            {
                _controlBufferGCHandle = GCHandle.Alloc(_controlBuffer, GCHandleType.Pinned);
                _ptrControlBuffer = Marshal.UnsafeAddrOfPinnedArrayElement(_controlBuffer, 0);
            }

            // If single buffer we need a pinned 1 element WSABuffer.
            if (_buffer != null)
            {
                if (_wsaRecvMsgWSABufferArray == null)
                {
                    _wsaRecvMsgWSABufferArray = new WSABuffer[1];
                }
                _wsaRecvMsgWSABufferArray[0].Pointer = _ptrSingleBuffer;
                _wsaRecvMsgWSABufferArray[0].Length = _count;
                _wsaRecvMsgWSABufferArrayGCHandle = GCHandle.Alloc(_wsaRecvMsgWSABufferArray, GCHandleType.Pinned);
                _ptrWSARecvMsgWSABufferArray = Marshal.UnsafeAddrOfPinnedArrayElement(_wsaRecvMsgWSABufferArray, 0);
            }
            else
            {
                // Just pin the multi-buffer WSABuffer.
                _wsaRecvMsgWSABufferArrayGCHandle = GCHandle.Alloc(_wsaBufferArray, GCHandleType.Pinned);
                _ptrWSARecvMsgWSABufferArray = Marshal.UnsafeAddrOfPinnedArrayElement(_wsaBufferArray, 0);
            }

            // Fill in WSAMessageBuffer.
            unsafe
            {
                Interop.Winsock.WSAMsg* pMessage = (Interop.Winsock.WSAMsg*)_ptrWSAMessageBuffer; ;
                pMessage->socketAddress = _ptrSocketAddressBuffer;
                pMessage->addressLength = (uint)_socketAddress.Size;
                pMessage->buffers = _ptrWSARecvMsgWSABufferArray;
                if (_buffer != null)
                {
                    pMessage->count = (uint)1;
                }
                else
                {
                    pMessage->count = (uint)_wsaBufferArray.Length;
                }

                if (_controlBuffer != null)
                {
                    pMessage->controlBuffer.Pointer = _ptrControlBuffer;
                    pMessage->controlBuffer.Length = _controlBuffer.Length;
                }
                pMessage->flags = _socketFlags;
            }
        }