Try this:
Private Sub getlist_Click(sender As Object, e As EventArgs) Handles getlist.Click
Dim aclient As New Net.WebClient
aclient.Credentials = New Net.NetworkCredential("****", "****")
Dim a As String
a = aclient.DownloadString("ftp://URL.chat.txt")
Dim b As String() = a.Split(vbLf)
ListBox1.Items.AddRange(b)
Hope this helps.