You can turn a bitmap into an array of bytes with this:
' You can use your own bitmap object. This one is just for illustration.
Dim myBitmap As New Bitmap(1280, 1024, PixelFormat.Format32bppArgb)
' Create a Rectangle object the size of the entire bitmap.
Dim rect As New Rectangle(0, 0, myBitmap.Width, myBitmap.Height)
' LockBits on the bitmap so we can get at the image data.
Dim imageData As BitmapData = myBitmap.LockBits(rect, ImageLockMode.ReadOnly, myBitmap.PixelFormat)
' Get a pointer to the first byte of the image data.
Dim ptrByte0 As IntPtr = imageData.Scan0
' Get the number of bytes used to store the bitmap data.
Dim numBytes As Integer = imageData.Stride * imageData.Height
' Create an array to hold all the bytes comtaining the image data.
Dim byteData(numBytes - 1) As Byte
' Make a copy of the image data to our array.
Marshal.Copy(ptrByte0, byteData, 0, numBytes)
' Release the lock.
myBitmap.UnlockBits(imageData)
Now you've got an array containing all the image data. What you do with this is up to you, but now it's in a format (an array) that can be sent using a UdpClient.