Android Question UknownHostException

#Region  Project Attributes
    #ApplicationLabel: B4A Example
    #VersionCode: 1
    #VersionName:
    'SupportedOrientations possible values: unspecified, landscape or portrait.
    #SupportedOrientations: unspecified
    #CanInstallToExternalStorage: False
#End Region

#Region  Activity Attributes
    #FullScreen: False
    #IncludeTitle: True
#End Region

Sub Process_Globals
    'These global variables will be declared once when the application starts.
    'These variables can be accessed from all modules.
    Dim ht As HttpJob
    Dim strResponse As String
End Sub

Sub Globals
    'These global variables will be redeclared each time the activity is created.
    'These variables can only be accessed from this module.
    Private btnTry As Button
    Private btnShow As Button
End Sub

Sub Activity_Create(FirstTime As Boolean)
    'Do not forget to load the layout file created with the visual designer. For example:
    'Activity.LoadLayout("Layout1")
   
    Activity.LoadLayout("Main")
   
   
End Sub

Sub JobDone(job As HttpJob)
ProgressDialogHide
'ToastMessageShow (job.JobName ,False)
If job.Success Then
    ToastMessageShow("Success",False)
    ToastMessageShow(job.GetString,True)
Else
    ToastMessageShow("No Success", False)
    ToastMessageShow(job.ErrorMessage,True)
End If

End Sub


Sub Activity_Resume
   
    strResponse = File.GetText(File.DirAssets,"trial.txt")
    strResponse = strResponse.Replace("$string$","hatzisn")
   
End Sub

Sub Activity_Pause (UserClosed As Boolean)

End Sub



Sub btnTry_Click
    ht.Initialize("WS",Me)
    ProgressDialogShow ("Connecting...")
    ht.poststring("http://servername.com/synproj/nikos/webservice.asmx", strResponse)
    ht.GetRequest.SetContentType("text/xml; charset=utf-8")
    ht.GetRequest.SetHeader("SOAPAction", """http://trial.net/CheckIfUserExist""")
End Sub
Sub btnShow_Click
    ToastMessageShow(strResponse,True)
End Sub