Re: How is this conditional able to execute?

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New Zealand? Very nice. Haven't been there yet but I've seen plenty of
photos and video of it. I imagine you take advatnage of the outdoors there.

You're right about this thread. Here's my email: brett1_at_cygen_dot_com

Thanks again,
Brett
"Stephany Young" <noone@localhost> wrote in message
news:u7BzhlZRFHA.3076@xxxxxxxxxxxxxxxxxxxxxxx
> Good morning.
>
> No, New Zealand - Just gone 11:00 PM (Wednesday) here.
>
> This thread is getting very long and no one else seems to be paying
> attention.
>
> If you like, we might continue this by email.
>
> If so, can you post a disguised email addy that I can decipher and we'll
> take it from there.
>
>
> "Brett" <no@xxxxxxxx> wrote in message
> news:uOCFefZRFHA.996@xxxxxxxxxxxxxxxxxxxxxxx
>>
>> "Stephany Young" <noone@localhost> wrote in message
>> news:ucW30eVRFHA.3496@xxxxxxxxxxxxxxxxxxxxxxx
>>> As I said, if you have:
>>>
>>> networkStream = tcpClient.GetStream()
>>>
>>> inside the loop, then each time the loop iterates then a NEW reference
>>> to the NetworkStream object is being obtained at a rate rate of 2 times
>>> every second.
>>>
>>> It is not necessary to do this and, as I also said, I think it is one of
>>> the causes of your problems.
>>>
>>> What I am trying to say, without upsetting you, is - having it inside
>>> the loop is plain downright dumb.
>>>
>>> The 'If networkStream.DataAvailable Then' has a matching 'End If'. It
>>> the one directly before the 'Catch ...'.
>>> Note that the test of returndata is not a type. It is all on one line.
>>> Because of this it does not have (does not need) an 'End If'. To put it
>>> back in you must have split the line which is not what I intended. The
>>> code I posted was copied and pasted from a project where the code works
>>> as shown.
>>>
>>
>> To leave the end if off is to get a compiler error. I don't know how you
>> are able to compile without. Perhaps you didn't paste all of the code?
>>
>>> We keep coming back to the question, how do you know that returndata is
>>> equal to "" when the code hits the test? What mechanism are you using to
>>> tell you this? We've been asking that from the start but you have never
>>> told us.
>>
>> I see this in the output and watches windows. I can also see it when I
>> mouse over the variable.
>>
>> I did try to run some previous code but received an error. I don't think
>> you saw my reply to it:
>>
>> Console.Writeline("mystring.Length = {0}", mystring.Length)
>> For _i As Integer = 0 To mystring.Length
>> Select Case CType(mystring.Chars(_i), Integer)
>> Case Is < 32, Is > 126
>> Console.Writeline("Character {0} found at position {1}",
>> CType(mystring.Chars(_i), Integer), _i)
>> End Select
>> Next
>>
>> I pasted in the above but get the following error on both occurances of
>> the
>> following:
>> mystring.Chars(_i)
>>
>> 'Char' values cannot be converted to 'Integer'. Use
>> 'Microsoft.VisualBasic.AscW' to interpret a character as a unicode value
>> or
>> 'Microsoft.Visualbasic.Val' to interpret it as a digit.
>>
>>>
>>> If, as you think, returndata = "" when the test is hit then the test
>>> will evaluate to False and the conditional code will NOT be executed.
>>>
>>> Put this in a new project an try it:
>>>
>>> Dim returndata As String = ""
>>> Dim ClientForm_ReturnData As String = "xyz"
>>> Console.WriteLine("returndata = *{0}*", returndata)
>>> If returndata <> "" AndAlso returndata <> ClientForm_ReturnData Then
>>> Console.WriteLine("Changing")
>>> ClientForm_ReturnData = returndata
>>> End If
>>> Console.WriteLine("ClientForm_ReturnData = {0}", ClientForm_ReturnData)
>>>
>>
>> Here's some of my output starting with the first iteration:
>>
>> returndata.length = 36
>> returndata = Connection accepted:06:52:56.5599165
>> Changing
>> ClientForm.ReturnData = Connection accepted:06:52:56.5599165
>> returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = Unable to write data to the transport
>> connection.Connected: BrettsLaptop 192.168.2.251returndata = Unable to
>> write data to the transport connection.Connected: BrettsLaptop
>> 192.168.2.251returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 5641
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>> ClientForm.ReturnData = returndata = returndata.length = 8192
>> Changing
>>
>> You can see returndata is the empty string above yet your IF is executed.
>> Meaning, it's saying If returndata <> "". Correct?
>>
>>> The result should be:
>>>
>>> returndata = **
>>> ClientForm_ReturnData = xyz
>>>
>>> Now change Dim returndata As String = "" to Dim returndata As String =
>>> "abc" and run it again.
>>>
>>> The result should be:
>>>
>>> returndata = *abc*
>>> Changing
>>> ClientForm_ReturnData = abc
>>> abc
>>> Now change Dim returndata As String = "" to Dim returndata As String =
>>> "xyz" and run it again.
>>>
>>> The result should be:
>>>
>>> returndata = *xyz*
>>> ClientForm_ReturnData = abc
>>>
>>> Not that 'Changing' is only displayed when returndata is NOT an empty
>>> string and returndata is NOT equal to ClientForm_ReturnData.
>>>
>>> If you are sure that the conditional code is being executed when (you
>>> think) returndata = "" then returndata does not contain what you think
>>> it does. To see what is actually in it, go back to dumping out the
>>> values of the individual bytes.
>>>
>>> Try this:
>>>
>>> Dim _b() As Byte = New Byte() {0, 0, 0}
>>> Dim _s As String = System.Text.Encoding.UTF8.GetString(_b)
>>> Console.WriteLine("_s.Length = {0}", _s.Length)
>>> Console.WriteLine("_s = *{0}*", _s)
>>>
>>> Note that the length of the string is 3 but that nothing shows after the
>>> first *.
>>>
>>> Change Dim _b() As Byte = New Byte() {0, 0, 0} to Dim _b() As Byte = New
>>> Byte() {54, 0, 0}
>>>
>>> Run it again and note that while the length of the string is still 3,
>>> the string shows as "6". Also note that the trailing * is not shown.
>>>
>>> Change Dim _b() As Byte = New Byte() {54, 0, 0} to Dim _b() As Byte =
>>> New Byte() {54, 54, 54}
>>>
>>>
>>> Run it again and note that the length of the string is still 3, the
>>> string shows as "666" and both *'s show.
>>>
>>> What you are seeing is the effect of Null or Chr(0) characters in the
>>> string, and you need to learn how to handle them.
>>>
>>> Change Dim _b() As Byte = New Byte() {54, 54, 54} to Dim _b() As Byte =
>>> New Byte() {54, 0, 0}
>>>
>>> Change Dim _s As String = System.Text.Encoding.UTF8.GetString(_b) to Dim
>>> _s As String =
>>> System.Text.Encoding.UTF8.GetString(_b).Trim(Char.MinValue)
>>>
>>> Run it again and note that the length of the string is now 1, the string
>>> shows as "6" and both *'s show.
>>>
>>> This is the result of trimming leading/trailing Null characters from the
>>> string.
>>>
>>> In addition, what value do you get for bytesread after the
>>> networkStream.Read? It is possible, but I would be surprised if it is
>>> actually 8192.
>>
>> Check the above output.
>>
>>>
>>> The next question is, what is the server end of the connection actually
>>> supposed to be sending?
>>
>> It does a filewatch and will send back a file path if certain files has
>> been modified.
>>
>>> Don't go to bed so early tonight, it's only mid-afternoon here :)
>>
>> Couldn't help it last night. The last few nights caught up with me.
>>
>>> PS: You might be getting the impression that I'm sounding a bit crabby,
>>> but I'm not really.
>>
>> You in Europe Stephany?
>>
>>>
>>>
>>> "Brett" <no@xxxxxxxx> wrote in message
>>> news:%234tqQ%23URFHA.3628@xxxxxxxxxxxxxxxxxxxxxxx
>>>> Thanks Stephany. This is super helpful.
>>>>
>>>> Why is this part out of the loop:
>>>> Dim networkStream As NetworkStream = tcpClient.GetStream()
>>>>
>>>> Also, your first IF:
>>>> If networkStream.DataAvailable then
>>>>
>>>> didn't have an ending END IF. I put on just before the catch. Is that
>>>> correct?
>>>>
>>>> This conditional is still being executed when returndata = ""
>>>> If returndata <> "" AndAlso returndata <>
>>>> ClientForm.ReturnData Then
>>>> ClientForm.ReturnData = returndata
>>>> End If
>>>> Maybe I just don't understand the returndata = "" because of the byte
>>>> array. But it seems you are testing the same conditions I did before.
>>>> So the above will always execute because the array always has 8192
>>>> length and somehow that makes returndata pass on returndata <> "".
>>>>
>>>> How can I read the string in :
>>>> Dim returndata As String = Encoding.UTF8.GetString(bytes, 0,
>>>> bytesread)
>>>> returndata gets the empty string here, although it really isn't, as
>>>> have seen previously.
>>>>
>>>> thanks,
>>>> brett
>>>>
>>>> "Stephany Young" <noone@localhost> wrote in message
>>>> news:eJau0ZURFHA.576@xxxxxxxxxxxxxxxxxxxxxxx
>>>>> 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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