Re: How is this conditional able to execute?

The mist is clearing.

If I've misunderstood anything please let me know because I'm still making
some assumptions.

I suspect that your starting point for the Try ... Catch ... End Try section
is the example shown in the documentation on the TcpClient.GetStream method.

What you have done is wrapped it in a loop and added some embellishments and
that example was not quite designed for that to be done to it. The example
was designed for a one-time run and to drop through the logic to whatever
followed. In your case you want the loop to continue until certain
conditions are met or the program ends. To meet this need you need to do
things just a little differently.

I assume that ClientForm.utility is also a shared reference to some sort of
utiliy class and that ClientForm.Packet is declared in a similar fashion to
ClientForm.ReturnData.

If I am correct in that ConnectInit is outside the thread then you shouldn't
be attempting to reinstate a 'broken' connection within the thread. If a
'broken' connection is detected you should allow the thread to 'die', then
reconnect, then start a new instance of the thread.

Before the start of loop you are obtaining a reference to the NetworkStream
object of the TcpClient object. In addidition, on each iteration of the loop
you are obtaining a fresh reference to the NetworkStream object of the
TcpClient object. There is no reason to do this. Don't quote me on this but
I suspect that doing so will cause you problems.

The declaration of the 'bytes' array should not need to be inside the loop.
Creating a new array on every iteration is not necessary. When you read the
NetworkStream object, the data will overwrite what is already in the array.
of course the array should be created with 8192 elements by using
tcpClient.ReceiveBufferSize - 1 rather than the 8193 elements you will get
if you simply use tcpClient.ReceiveBufferSize.

The NetworkStream.Read method, as well as filling the array, also returns an
integer indicating the number of bytes successfully read into the array. You
should make use of this to control what you are dealing with. Remember that
tcpClient.ReceiveBufferSize is the maximum number of bytes that can be read
at any one time rather than the number of bytes that are actually read.

For the third parameter to the NetworkStream.Read method, it is, in my
opinion, better to use bytes.Length rather than tcpClient.ReceiveBufferSize
because bytes.Length is the actual number of elements in the array.

I think that the tests of the NetworkStream.CanWrite and
NetworkStream.CanRead are probably redundant, unless you are opening the
sockets at either end with specfic read/write restrictions.

Another important point is that the NetworkStream.Read method will block
until data is available. This is probably undesirable but can be
circumvented by using the NetworkStream.DataAvailable property. This will
allow your loop to iterate in a timely manner.

Now that we know exactly how many bytes were read from the NetworkStream
object, we can use the appropriate Encoding.GetString overload to make sure
that our string is a representation of only those bytes. This should do away
with the need for any 'trimming' of the resulting string.

Where you have the test for NetworkStream.DataAvailable is inappropriate and
I get the impression that you might not fully understand it's use.

On the test of returndata, the .ToString is redundant because returndata is
already a string. The parenthesis are also redundant. In addition, using
AndAlso will be better than And here because if returndata is an empty
string then the second part of the test will not be evaluated if AndAlso is
used whereas it will be evaluated if just And is used. The logic is that if
the evaluation of first part fails then why bother evaluating the second
part at all. This is clled 'short-circuiting' and is a very useful technique
when used appropriately. Setting returndata to Nothing is redundant because
returndata is going to be created anew on the next iteration of the loop.
Likewise, the 'Else' that does nothing is also redundant.

As you can see, the resulting code is more compact and now, that the
appropriate techniques are being used, should work quite happily.

What is left to do, of course, is for you to add the appropriate code to
'tear-down' the thread in a friendly fashion when the program needs to
terminate or you need to stop the thread for some other reason.


Code as supplied by Brett
-------------------------

In ClientForm
-------------
Public Shared ReturnData As String
Public Shared Packet As String ' or something like that
Public Shared utility As UtilityClass = New UtilityClass ' or something
like that
-------------


Dim ConnectAttempts As Integer = 0
Dim t As Thread

Dim Packet As String
Dim InitialIDSent As Boolean = False

Dim tsGap As TimeSpan
Dim dtStart As DateTime = Now

ConnectInit()

Within thread
-------------
Dim networkStream As NetworkStream = tcpClient.GetStream()

While True
Try

If networkStream.CanWrite And networkStream.CanRead Then

networkStream = tcpClient.GetStream()

Dim bytes(tcpClient.ReceiveBufferSize) As Byte
networkStream.Read(bytes, 0, tcpClient.ReceiveBufferSize)
Dim returndata As String =
Trim(Encoding.UTF8.GetString(bytes).Trim(Char.MinValue))

If InitialIDSent Then
Packet = "Nothing to Write from: " & Thread.CurrentThread.Name
Else
Packet = "Connected: " & ClientForm.Packet
InitialIDSent = True
'write to log file
ClientForm.utility.WriteToFile(ClientForm.CurrentDirectory.GetCurrentDirectory,
ClientForm.LogFileExec, ClientForm.utility.CurrentDateTime(0) & " -
Connected: " & ClientForm.Packet)
End If

' Do a simple write.
Dim sendBytes As [Byte]() = Encoding.ASCII.GetBytes(Packet.TrimEnd)
networkStream.Write(sendBytes, 0, sendBytes.Length)

If networkStream.DataAvailable() Then
If (returndata <> "") And returndata.ToString <>
ClientForm.ReturnData Then
ClientForm.ReturnData = returndata
returndata = Nothing

Else
End If
End If

End If

Catch ex As Exception

If ex.Message = "Operation not allowed on non-connected sockets." Then
ConnectInit()
ConnectAttempts = +1

If ConnectAttempts > 5 Then
Exit Sub
End If
Else
End If
Exit While
End Try

Thread.CurrentThread.Sleep(500)
End While
-------------


Code as modified by Stephany
----------------------------

In ClientForm
-------------
Public Shared ReturnData As String
Public Shared Packet As String ' or something like that
Public Shared utility As UtilityClass = New UtilityClass ' or something
like that
-------------


Dim ConnectAttempts As Integer = 0
Dim t As Thread

Dim Packet As String
Dim InitialIDSent As Boolean = False

Dim tsGap As TimeSpan
Dim dtStart As DateTime = Now

ConnectInit()

Within thread
-------------
Dim networkStream As NetworkStream = tcpClient.GetStream()

Dim bytes(tcpClient.ReceiveBufferSize - 1) As Byte

Dim bytesread As Integer

While True
Try
If networkStream.DataAvailable then
bytesread = networkStream.Read(bytes, 0, bytes.Length)
Dim returndata As String = Encoding.UTF8.GetString(bytes, 0,
bytesread)
If InitialIDSent Then
Packet = "Nothing to Write from: " & Thread.CurrentThread.Name
Else
Packet = "Connected: " & ClientForm.Packet
InitialIDSent = True
'write to log file
ClientForm.utility.WriteToFile(ClientForm.CurrentDirectory.GetCurrentDirectory,
ClientForm.LogFileExec, ClientForm.utility.CurrentDateTime(0) & " -
Connected: " & ClientForm.Packet)
End If
' Do a simple write.
Dim sendBytes() As Byte = Encoding.ASCII.GetBytes(Packet.TrimEnd)
networkStream.Write(sendBytes, 0, sendBytes.Length)
If returndata <> "" AndAlso returndata <> ClientForm.ReturnData Then
ClientForm.ReturnData = returndata
End If
Catch ex As Exception
Exit While
End Try
Thread.CurrentThread.Sleep(500)
End While
-------------



.

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