write time out error

Public Class clsSMS

#Region "Open and Close Ports"
'Open Port
Public Function OpenPort(ByVal p_strPortName As String, ByVal p_uBaudRate As Integer, ByVal p_uDataBits As Integer, ByVal p_uReadTimeout As Integer, ByVal p_uWriteTimeout As Integer) As SerialPort
receiveNow = New AutoResetEvent(False)
Dim port As New SerialPort()

Try
port.PortName = p_strPortName 'COM1
port.BaudRate = p_uBaudRate '9600
port.DataBits = p_uDataBits '8
port.StopBits = StopBits.One '1
port.Parity = Parity.None 'None
port.ReadTimeout = p_uReadTimeout '300
port.WriteTimeout = p_uWriteTimeout '300
port.Encoding = Encoding.GetEncoding("iso-8859-1")
AddHandler port.DataReceived, AddressOf port_DataReceived
port.Open()
port.DtrEnable = True
port.RtsEnable = True
Catch ex As Exception
Throw ex
End Try
Return port
End Function

'Close Port
Public Sub ClosePort(ByVal port As SerialPort)
Try
port.Close()
RemoveHandler port.DataReceived, AddressOf port_DataReceived
port = Nothing
Catch ex As Exception
Throw ex
End Try
End Sub

#End Region

'Execute AT Command
Public Function ExecCommand(ByVal port As SerialPort, ByVal command As String, ByVal responseTimeout As Integer, ByVal errorMessage As String) As String
Try

port.DiscardOutBuffer()
port.DiscardInBuffer()
receiveNow.Reset()
port.Write(command & vbCr)

Dim input As String = ReadResponse(port, responseTimeout)
If (input.Length = 0) OrElse (((Not input.EndsWith(vbCrLf & "> "))) AndAlso ((Not input.EndsWith(vbCrLf & "OK" & vbCrLf)))) Then
Throw New ApplicationException("No success message was received.")
End If
Return input
Catch ex As Exception
Throw ex
End Try
End Function

'Receive data from port
Public Sub port_DataReceived(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs)
Try
If e.EventType = SerialData.Chars Then
receiveNow.Set()
End If
Catch ex As Exception
Throw ex
End Try
End Sub
Public Function ReadResponse(ByVal port As SerialPort, ByVal timeout As Integer) As String
Dim buffer As String = String.Empty
Try
Do
If receiveNow.WaitOne(timeout, False) Then
Dim t As String = port.ReadExisting()
buffer &= t
Else
If buffer.Length > 0 Then
Throw New ApplicationException("Response received is incomplete.")
Else
Throw New ApplicationException("No data received from phone.")
End If
End If
Loop While (Not buffer.EndsWith(vbCrLf & "OK" & vbCrLf)) AndAlso (Not buffer.EndsWith(vbCrLf & "> ")) AndAlso Not buffer.EndsWith(vbCrLf & "ERROR" & vbCrLf)
Catch ex As Exception
Throw ex
End Try
Return buffer
End Function

#Region "Count SMS"
Public Function CountSMSmessages(ByVal port As SerialPort) As Integer
Dim CountTotalMessages As Integer = 0
Try

' #Region "Execute Command"

Dim recievedData As String = ExecCommand(port, "AT", 300, "No phone connected at ")
recievedData = ExecCommand(port, "AT+CMGF=1", 300, "Failed to set message format.")
Dim command As String = "AT+CPMS?"
recievedData = ExecCommand(port, command, 1000, "Failed to count SMS message")
Dim uReceivedDataLength As Integer = recievedData.Length

' #End Region

' #Region "If command is executed successfully"
If (recievedData.Length >= 45) AndAlso (recievedData.StartsWith("AT+CPMS?")) Then

' #Region "Parsing SMS"
Dim strSplit() As String = recievedData.Split(","c)
Dim strMessageStorageArea1 As String = strSplit(0) 'SM
Dim strMessageExist1 As String = strSplit(1) 'Msgs exist in SM
' #End Region

' #Region "Count Total Number of SMS In SIM"
CountTotalMessages = Convert.ToInt32(strMessageExist1)
' #End Region

' #End Region

' #Region "If command is not executed successfully"
ElseIf recievedData.Contains("ERROR") Then

' #Region "Error in Counting total number of SMS"