System.Net.Sockets中，无法定义连接超时时间

  Sub Main(ByVal args As String())
        Dim strTxt As String = ""
        Dim PathName As String = args(0)
        Dim sReader As StreamReader
        sReader = New StreamReader(PathName, Encoding.Default)
        Dim S As String
        S = sReader.ReadLine()
        While Not S Is Nothing
            If UrlExist(S.ToString) = True Then
                Console.WriteLine(S.ToString & "|" & "True")
            Else
                Console.WriteLine(S.ToString & "|" & "False")
            End If
            S = sReader.ReadLine()
        End While
        sReader.Close()
    End Sub


    Public Function UrlExist(ByVal sURL As String) As Boolean
        Dim temp As Boolean = False
        Try
            ' Dim ip As IPAddress = IPAddress.Parse("218.5.78.118")
            Dim ip As String = Dns.GetHostByName(sURL).AddressList(0).ToString()
            Dim sock As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
            'sock.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.Error, 5000) 没效果
            'sock.SetSocketOption(SocketOptionLevel.Tcp,SocketOptionName.SendTimeout,5000) 
            sock.Connect(ip, 80)
            sock.Close()
            temp = True
        Catch e As SocketException
            temp = False
        End Try

        Return temp
    End Function