以下代码 为获取北京 ，在命令状态下，执行此代码 出现三种情况，1.执行准确 2.无法获取 3。什么也没有显示

而且执行时间较长，请指教

Dim TimeServers As String(,) = New String(2, 1) {}
TimeServers(0, 0) = "time-b.timefreq.bldrdoc.gov"
TimeServers(0, 1) = "132.163.4.102"
TimeServers(1, 0) = "time-c.timefreq.bldrdoc.gov"
TimeServers(1, 1) = "132.163.4.103"
TimeServers(2, 0) = "utcnist.colorado.edu"
TimeServers(2, 1) = "128.138.140.44"

Dim portNum As Integer = 13
Dim hostName As String
Dim bytes As Byte() = New Byte(1023) {}
Dim bytesRead As Integer = 0
Dim client As New System.Net.Sockets.TcpClient()
For i As Integer = 0 To 2
    hostName = TimeServers(i, 1)
    Try
        client.Connect(hostName, portNum)
        Dim ns As System.Net.Sockets.NetworkStream = client.GetStream()
        bytesRead = ns.Read(bytes, 0, bytes.Length)
        client.Close()
       
        Exit For
    Catch generatedExceptionName As System.Exception
    End Try
Next
Dim sp As Char() = New Char(0) {}
sp(0) = " "c
Dim dt As System.DateTime = New DateTime()
Dim str1 As String
str1 = System.Text.Encoding.ASCII.GetString(bytes, 0, bytesRead)

If str1 >"" Then
    Dim s As String()
    s = str1.Split(sp)
    dt = System.DateTime.Parse(s(1) & " " & s(2))
    \'得到标准时间
    dt = dt.AddHours(8)
    \'得到北京时间
    Dim getdate As Date
    getdate=dt.Date
    messagebox.show(getdate)
   Else
    messagebox.show("获取时间失败")
End If