how to create a program that receives messages using at commands in vb 2010?

hey guys i really need some help.

i tried this codes below that i created but it cant receive messages. and if it can i like to read it directly in Richtextbox.

here is the code:

Public Sub receive()
If srPort.IsOpen = True Then
Try

With srPort
.WriteLine("AT")
.WriteLine("AT+CMGF=1" & Chr(34) & vbCrLf)
.WriteLine("AT+CSCS=""PCCP437""" & Chr(34) & vbCrLf)
.WriteLine("AT+CPMS=""SM""" & Chr(34) & vbCrLf)
.WriteLine("AT+CMGL=""REC UNREAD""" & receiveRT.Text & vbCrLf)


End With
Catch ex As Exception

End Try

End If
End Sub