[RESOLVED] Hidden Characters after sending text via TCP

[menathang]

Hi, I'm new to the forums so please forgive me if I post this in the wrong section.
Anyway I'm having a problem where if I convert a string to bytes then send it through TCP, on the other end it does not convert properly. The original string is present in the received bytes although there appears to be some hidden characters stopping me from using a select case. Rough code is below...

Private Sub Listen()
 
        Dim LST_PORT as int16 = 9292    'Port to listen on'
        Dim TCP_LISTEN As TcpListener = New TcpListener(LST_PORT)
        TCP_LISTEN.Start()
 
        Try
 
            Dim TCP_CLIENT As TcpClient = TCP_LISTEN.AcceptTcpClient
 
            Dim NET_STREAM As NetworkStream = TCP_CLIENT.GetStream
 
            'reading data'
            Dim bytes(TCP_CLIENT.ReceiveBufferSize) As Byte
 
            NET_STREAM.Read(bytes, 0, TCP_CLIENT.ReceiveBufferSize)
 
            Dim RX_STRING As String = Encoding.ASCII.GetString(bytes)
 
 
            Select Case RX_STRING.Trim.ToUpper
 
                Case "1"
                    Console.Beep()
                Case "SHUTDOWN"
                    Process.Start("shutdown", "-f -s -t 00")
 
                Case Else
 
                    MsgBox(RX_STRING, MsgBoxStyle.OkOnly, "...")
 
 
            End Select
 
            TCP_CLIENT.Close()
 
        Catch ex As Exception
 
        End Try
        TCP_LISTEN.Stop()
 
 
    End Sub

Problem is if I send "beep" from the client program, rather than beeping the program instead follows the 'case else' and displays "beep" in a message box.
Any help would be very much appreciated. Thank you.

[dbasnett]

Change
Case "1"
Console.Beep()


to

Case "beep"
Console.Beep()

[menathang]

Thanks for the reply, I should probably say that "1" used to say beep and that I just switched it to test. I have the same problem with sending "shutdown" so its not something as simple as that. Thanks for picking up on my mistake though

[cicatrix]

Encoding.ASCII.GetString(bytes)

ASCII - that's the problem, I think. Try Unicode.

[dbasnett]

It might be helpful to see what was sent. What is in bytes after
NET_STREAM.Read(bytes, 0, TCP_CLIENT.ReceiveBufferSize)

[menathang]

Thanks cicatrix but that didn't seem to make a difference when I tried.
dbasnett, on the client application I have used the same method, eg:

Dim SendBytes() as byte
Dim SendString as string = "SHUTDOWN"

SendBytes = Encoding.ASCII.getbytes()

netstream.Write(SendBytes, 0, SendBytes.Length)

I have also tried replacing "SHUTDOWN" with "BEEP" or in this case "1". It's just frustrating, the string starts of right but comes out somehow messed up. It's perfectly readable but won't go through a select case or if statement. And in the server which is a console application, it appears as if there are extra lines under the string that is received, I even tried trimming the string to no avail.

As I said though, what is sent is "SHUTDOWN", what seems to come back is "SHUTDOWN" with a few extra blank lines.

[cicatrix]

What does Debug.Writeline(RX_STRING.Trim.ToUpper) show in the Sub Listen?

Try to use StreamReader/StreamWriter instead of manual conversion to byte array

[dbasnett]

It might be helpful to see what was sent. What is in bytes after
NET_STREAM.Read(bytes, 0, TCP_CLIENT.ReceiveBufferSize)

bytes(0)=
bytes(1)=
bytes(2)=
etc.
?????????????????????

[menathang]

Originally Posted by dbasnett
It might be helpful to see what was sent. What is in bytes after
NET_STREAM.Read(bytes, 0, TCP_CLIENT.ReceiveBufferSize

Ok, I had a look and for the word "beep" I get the following for the first 6 elements,

bytes(0)=98
bytes(1)=101
bytes(2)=101
bytes(3)=112
bytes(4)=0
bytes(5)=0

is the problem maybe something to do with the buffer size?, should there even be a 5th, 6th element, etc...

I will also try using stream reader as cicatrix suggests if I can work that out, I use it for writing text files but that's about it usually. I'll take a look.

Thank you for your help

[dbasnett]

What does the send routine look like?

[menathang]

Private Sub SendP()
 
      
 
        Dim SendString As String = "beep"
 
        Dim tcpClient As New System.Net.Sockets.TcpClient
        Try
            tcpClient.Connect(HostAddress, Port)
        Catch ex As Exception
            MsgBox("Socket Err on port " & Port & "." & vbCrLf & ex.Message.ToString)
            tcpClient.Close()
            Console.ReadLine()
 
            Exit Sub
 
        End Try
 
 
        Dim netstream As NetworkStream = tcpClient.GetStream
 
        If netstream.CanRead And netstream.CanWrite Then
 
            'Write'
 
            Dim sendbytes() As Byte = Encoding.ASCII.GetBytes(SendString)
            MsgBox(sendbytes.Length)
            tcpClient.SendBufferSize = sendbytes.Length
 
            netstream.Write(sendbytes, 0, sendbytes.Length)
 
 
 
        Else
            MsgBox("Socket Error, port " & Port)
            tcpClient.Close()
 
 
        End If
 
        Console.Write("String Sent on port " & Port)
 
        tcpClient.Close()
        Console.Clear()
 
       
    End Sub

Some extra info: The buffer size being sent is correct, eg the word beep has a buffer of length 4. On the other side I can't seem to retrieve the right size through recievebufferlength which always defaults at 8192 so the byte array on the server side is full of useless zeros...

[dbasnett]

So the answer might be to make all of the commands a fixed length:

    Dim maxC As Integer = -1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim commands() As String = New String() {"shutdown", "beep", "hello"}
        For Each s As String In commands
            If s.Length > maxC Then maxC = s.Length
        Next

        Dim command2Send As String
        command2Send = foo(commands(0))
        command2Send = foo(commands(1))
        command2Send = foo(commands(2))


        Select Case command2Send.Trim

        End Select
    End Sub

    Private Function foo(ByVal s As String) As String
        foo = s.PadRight(maxC, " "c)
    End Function

[menathang]

Thanks, I think I might just do that as a nice way out. Starting a new computer science degree anyway so I might learn a trick when I do network programming

Set length seems to work for now until I find a better way.