Question

problems in data over socket

Asked by: jaxrpc

Hi,

I am trying to communicate with an external device and i am trying to send a byte array to the external device via sockets but i am always getting a response the message size is too small so i am not sure what i have done wrong. Between the data type there should be no alignment present and all numbers are represented in little endian format. The char array is not null terminated as mentioned in the protocol specifications.

I have to send data based on a struct that embeds 2 other struct. So here's my vb.net code for the struct used to convert to byte array and the sending part. Thanks in advance.

'Structures
Public Structure MESSAGETYPE_OIP_Login
        Dim Header() As COMMANDHEADER
        Dim UserName() As PSTRING
        Dim Password() As PSTRING
    End Structure
   
    Public Structure COMMANDHEADER
        Dim MessageType As UInt32
        Dim Length As UInt32
        Dim Reserved1 As UInt32
        Dim Reserved2 As UInt32
    End Structure
 
    Public Structure PSTRING
        Dim Length As UInt32
        Dim CharArray() As Char
    End Structure
 
'Conversion and sending part
Dim client as System.Net.Sockets.TcpClient = New  System.Net.Sockets.TcpClient("192.168.20.93", 9401)
 
Dim networkStream As Net.Sockets.NetworkStream = client.GetStream()
 
        Dim Login As MESSAGETYPE_OIP_Login
 
        Login.Header.MessageType = 4485122
        Login.Header.Reserved1 = 0
        Login.Header.Reserved2 = 0
        Login.Header.Length = Marshal.SizeOf(Login.Header)
 
        Login.UserName.CharArray = "admin".ToCharArray
        Login.UserName.Length = Login.UserName.CharArray.Length
 
        Login.Password.CharArray = "admin".ToCharArray
        Login.Password.Length = Login.Password.CharArray.Length
 
        Dim StrtoBy() As Byte
 
 
        Dim ptr As IntPtr = Marshal.AllocCoTaskMem(Marshal.SizeOf(Login))
        
        ReDim StrtoBy(Marshal.SizeOf(Login) - 1)
        Marshal.Copy(ptr, StrtoBy, 0, Marshal.SizeOf(Login))
        Marshal.FreeCoTaskMem(ptr)
 
        networkStream.Write(StrtoBy, 0, StrtoBy.Length)

                                  
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Asked On
2009-08-28 at 21:24:53ID24691584
Tags

Socket

,

Vb.net

,

byte array

,

structure

Topics

Microsoft Visual Basic.Net

,

.NET

,

Microsoft Visual C#.Net

Participating Experts
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Answers

 

by: CodeCruiserPosted on 2009-08-29 at 06:29:03ID: 25213987

What happens if you remove the -1 from this line?
  ReDim StrtoBy(Marshal.SizeOf(Login) - 1)

 

by: jaxrpcPosted on 2009-08-29 at 07:57:39ID: 25214255

hi,
it is still the same when i remove the -1.

by th e way i am not sure if i am doing it correctly. WHat i am trying to do is to convert complex structures (structure containing structure) to byte array and send it over the wire using sockets.

 

by: jaxrpcPosted on 2009-09-18 at 13:06:07ID: 25369527

.Net somehow don't maintain the order the data are laid out when using structToByte function and this causes problem to what i am trying to send over using sockets.

So what i did was to convert each of the data using bitconverter class 1 by 1 and send them using sockets 1 at a time. And it works.

20120131-EE-VQP-002

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