Imports System.Net

Imports System.Net.Sockets

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim ipAddr As IPAddress

        Dim remoteHostEntry As IPHostEntry

        Try

            ipAddr = IPAddress.Parse(TextBox1.Text)

            remoteHostEntry = Dns.GetHostByAddress(ipAddr)

            TextBox2.Text = (remoteHostEntry.HostName)

        Catch ex As SocketException

            TextBox2.Text = (ex.StackTrace.ToString)

        End Try

    End Sub

End Class