View Compilation Error

0_0_33306810_17301.cs(16,13): error CS0246: The type or namespace name 'IPAddress' could not be found (are you missing a using directive or an assembly reference?)
0_0_33306810_17301.cs(16,28): error CS0103: The name 'IPAddress' does not exist in the current context
0_0_33306810_17301.cs(18,38): error CS0246: The type or namespace name 'IPEndPoint' could not be found (are you missing a using directive or an assembly reference?)