hey guys i need some help. how to fix "the write timed out" in vb 2010?

here is the code:

Imports System.IO.Ports
Imports System
Imports System.Threading


Public Class Form2



Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
openport()

End Sub
Private Sub openport()
Dim ports As String() = SerialPort.GetPortNames
Dim port As String

For Each port In ports
cbPort.Items.Add(port)
Next port
cbPort.SelectedIndex = 0

End Sub



Private Sub btnConn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConn.Click

With srPort
Try

.PortName = cbPort.Text
.BaudRate = "19200"
.Parity = System.IO.Ports.Parity.None
.StopBits = System.IO.Ports.StopBits.One
.DataBits = 8
.WriteTimeout = 100
.Handshake = Handshake.RequestToSend
.DtrEnable = True
.RtsEnable = True
.NewLine = vbCrLf
srPort.Open()

MsgBox("Port now open")



Catch ex As Exception
MsgBox(ex.Message)
End Try

End With
End Sub

Private Sub SendRT_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SendRT.TextChanged
Dim send As String = SendRT.Text
Select Case send
Case "Shutting Down"
Try
shutdown()
Catch ex As Exception
MsgBox(ex.Message)
End Try

Case "The Computer is Now Restarting"
Try
shutdown()
Catch ex As Exception
MsgBox(ex.Message)
End Try
Case "The Computer will Now Hibernate"
Try
shutdown()
Catch ex As Exception
MsgBox(ex.Message)
End Try

End Select

End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Try
srPort.Close()
MsgBox("Disconnected")
Catch ex As Exception
MsgBox(ex.Message)
End Try

End Sub


Private Sub receiveRT_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles receiveRT.TextChanged
Dim str As String = receiveRT.Text
Select Case str
Case "Shutdown"
SendRT.Text = "Shutting Down"
Case "Restart"
SendRT.Text = "The Computer is Now Restarting"
Case "Hibernate"
SendRT.Text = "The Computer will Now Hibernate"
Case Else
SendRT.Text = ""
End Select
End Sub

Private Sub shutdown()

If srPort.IsOpen Then

With srPort
.Write("AT")
.Write("AT+CMGF=1" & vbCrLf)
.Write("AT+CMGS=" & Chr(34) & CNtbox.Text & Chr(34) & vbCrLf)
.Write(SendRT.Text & Chr(26))
receiveRT.Clear()
SendRT.Clear()
End With


End If


End Sub

End Class


basically i encountered that problem in the public sub shutdown(), where "the write timed out" occurs.


please help me fix this....