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

        internal unsafe SocketError DoOperationReceiveFrom(SafeCloseSocket handle, out SocketFlags flags, out int bytesTransferred)
        {
            PrepareIOCPOperation();

            flags = _socketFlags;

            SocketError socketError;
            if (_buffer != null)
            {
                socketError = Interop.Winsock.WSARecvFrom(
                    handle,
                    ref _wsaBuffer,
                    1,
                    out bytesTransferred,
                    ref flags,
                    _ptrSocketAddressBuffer,
                    _ptrSocketAddressBufferSize,
                    _ptrNativeOverlapped,
                    IntPtr.Zero);
            }
            else
            {
                socketError = Interop.Winsock.WSARecvFrom(
                    handle,
                    _wsaBufferArray,
                    _wsaBufferArray.Length,
                    out bytesTransferred,
                    ref flags,
                    _ptrSocketAddressBuffer,
                    _ptrSocketAddressBufferSize,
                    _ptrNativeOverlapped,
                    IntPtr.Zero);
            }

            if (socketError == SocketError.SocketError)
            {
                socketError = SocketPal.GetLastSocketError();
            }

            return socketError;
        }

        public bool ReceiveFromAsync(SocketAsyncEventArgs e)
        {
            bool retval;

            if (s_loggingEnabled)
            {
                Logging.Enter(Logging.Sockets, this, "ReceiveFromAsync", "");
            }

            if (CleanedUp)
            {
                throw new ObjectDisposedException(GetType().FullName);
            }

            if (e == null)
            {
                throw new ArgumentNullException("e");
            }
            if (e.RemoteEndPoint == null)
            {
                throw new ArgumentNullException("RemoteEndPoint");
            }
            if (!CanTryAddressFamily(e.RemoteEndPoint.AddressFamily))
            {
                throw new ArgumentException(SR.Format(SR.net_InvalidEndPointAddressFamily, e.RemoteEndPoint.AddressFamily, _addressFamily), "RemoteEndPoint");
            }

            // We don't do a CAS demand here because the contents of remoteEP aren't used by
            // WSARecvFrom; all that matters is that we generate a unique-to-this-call SocketAddress
            // with the right address family.
            EndPoint endPointSnapshot = e.RemoteEndPoint;
            e._socketAddress = SnapshotAndSerialize(ref endPointSnapshot);

            // DualMode sockets may have updated the endPointSnapshot, and it has to have the same AddressFamily as 
            // e.m_SocketAddres for Create to work later.
            e.RemoteEndPoint = endPointSnapshot;

            // Prepare for the native call.
            e.StartOperationCommon(this);
            e.StartOperationReceiveFrom();

            // Make the native call.
            SocketFlags flags;
            int bytesTransferred;
            SocketError socketError;

            try
            {
                socketError = e.DoOperationReceiveFrom(_handle, out flags, out bytesTransferred);
            }
            catch (Exception ex)
            {
                // Clear in-use flag on event args object. 
                e.Complete();
                throw ex;
            }

            // Handle completion when completion port is not posted.
            if (socketError != SocketError.Success && socketError != SocketError.IOPending)
            {
                e.FinishOperationSyncFailure(socketError, bytesTransferred, flags);
                retval = false;
            }
            else
            {
                retval = true;
            }

            if (s_loggingEnabled)
            {
                Logging.Exit(Logging.Sockets, this, "ReceiveFromAsync", retval);
            }
            return retval;
        }