TCP Connection Drops Out
Sep 25, 2011
I have written a application that has a TCP client and server to connect to a PLC. The Client works perfectly but it looks like the server drops out all the time. What happens is when I first start the connection it will update without any problems but after about 1min of no transfer the PLC can no longer send data to the application. Neither system gives an error and the PLC shows that it is transmitting the data but nothing comes through on the application side of things. I have tried to put in heartbeat to see if that would stop the drop out but to no avail.[code]
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Jul 15, 2011
I can't see anything in the method list that lets you know when a connection drops (and since it's constantly checking, it seems that could have been in there, to raise a flag when it can't find the connection anymore...no?). Is there a way to know if the network connection drops? Is there a way to reconnect it? Is it just a matter of turning EnableRaisingEvents() off and back on to re-establish the link to the network share?
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Feb 7, 2011
I built a dwonloader program which download a file from the web. I would like to insert an error message that pop up whenever the program fail to download the file and/or when the computer gets disconnected from the internet while the program is downloading the file.
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May 18, 2011
I have this app written in VB.Net with winforms that shows some stats and pictures on a bigscreen monitor.I also monitor the memory usage of sad app by using this. Process.WorkingSet64
I know windows does not always report the correct usage but I just wanted to know if I didn't have any little memory leaks which I had but are solved now. But the first week the memory usage was around 100MB and the second week the memory usage showed around 50MB.
So why did it all of a sudden drop while still running the exact same code?I can hardly imagine that the garbage collector kicked in this late since the app refreshes every 10 seconds and it has ample time in between those periods to do it's thing.Or perhaps there is just better way to get memory usage for a process that is more reliable.
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Aug 2, 2010
I've been using some code which I found on the net, and have noticed that the first byte is never recieved. Annoyingly, this contains the MAC addresses, which is the bit I want. Below is the relevant snippits:
Public Sub [Start]()
If m_Socket Is Nothing Then
Try
[Code].....
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Oct 2, 2010
I have 3 lists in my form.When 1 list is clicked, I want to drop the selection in the other 2 lists.
Private Sub lstPlaylist_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lstPlaylist.SelectedIndexChanged
lstArtist.ClearSelected()[code]....
This is my current code. When I click on lstPlaylist, it drops the selection for all lists.
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Nov 20, 2009
Several times while debugging a VB.Net program I have found that continuation lines are missing from a subroutine designed to handle an event. The continuation character "_" is there but the following line is missing
[Code]...
The first few times I figured I had made some editing error, but this has happened 3 times now, always in the same way (different subroutines but same place). As far as I can tell, no other continuation lines have changed. Is this a bug or some feature I have missed?
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Oct 27, 2010
[code] how to make the part that drops down semi-transparent or completely transparent resembling floating text. So that I can see the form underneath.
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Mar 26, 2012
I am writing some code as part of a framework for opening a file.The file is of custom type and should not be opened by more than one instance of my application. To stop multiple file opening I use a filestream to create a lock file and then keep said filestream open. This seems to work in preventing another instance of my application from opening the file ( as it will fail in recreating the lock stream in the files open code ) but if the file is on a network share and the network drops then the original application also can not access the file any more.The code to get the lock stream is as follows:
Try
' We need to keep this stream alive to prevent other applications gaining access to the lock
mLockStream = New FileStream(mLockPath, FileMode.CreateNew, FileAccess.Write, FileShare.None)[code]....
In this I create the lock stream the first time round and then if another application tries to create it, it throws an exception and stops them from getting any further. This is kind of how it needs to work, unfortunately as I said, if this is done across a network and then the network connection is dropped for some reason then I can not delete the lock stream as I get an IOException telling me a process cannot access the file as it is open in another process ( which shouldn't be happening I don't think).
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Aug 25, 2009
How do I assign a My.Settings.Item connection string to cmd.Connection connection string value?
Dim cmd As New SqlCommand()
cmd.Connection = My.Settings.Item("csStaffHoursWorked")
cmd.CommandType = CommandType.StoredProcedure
cmd.CommandText = "spSaveDeltekImport"
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Feb 5, 2010
Is there a way to display the connection properties dialog for connection string browsing(for database) in run time?
As I want the user to be able to connect to various database using the GUI.
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Aug 3, 2011
i have an application. which is executed after every 5 mins. i have an open connection but it gives me the following error:
ExecuteScalar requires an open and available Connection. The connection's current state is closed.
my code is something like this. I have shown where all i am using ExceuteScalar()
Sub Main()
Try
connection.open()
cmd.ExecuteScalar()
[code]....
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Aug 19, 2010
After running the following sub (VS debugger), I try to detach the database in SSMS, but it shows the connection open still and won't let me detach. If I close program in debugger, the database shows no connections. I check the dataadapter's connection in the finally block and is shows closed. What gives
Private Function ClientMasterDBFiles(ByVal MasterClientDBConnection As String, ByVal DBName As String) As DataTable
[Code]...
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Mar 15, 2009
I have a simple scraper. It works on some websites, but on some there is this Error:
Quote:
IOException was unhandled Unable to read data from the transport connection: The connection was closed
It is occuring at "Dim htmlresults As String = Urlcontents.ReadToEnd()".
'Create the HttpWebRequest object
Dim req As HttpWebRequest = WebRequest.Create(URL)
'Set the timeout to 1 second (or 1,000 milliseconds)
req.Timeout = 10000
[code]....
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Jun 21, 2010
I am attempting to write a program that will disable the Local Area Connection while leaving the Wireless connection enabled. My company is using net-books in our stores to demo air-cards and we need to keep them off of the LAN. I'm new to VB and VB.net, and it's been a while since I did any type of programming. I've gathered some code that others have posted in forums and tutorials and I'm working through a tutorial book, but I finally believe that I am stuck.
[Code]...
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Nov 30, 2008
i make a class and when i call on form then that error occurs "ExecuteNonQuery requires an open and available connection, the connection Current stat is close "
Class Code isImports System.Data.SqlClientImports System.DataImports System.StringPublic Class DatabaseKits Dim Cn As New SqlClient.SqlConnection Public Function BuildConnection() As Boolean Try Cn.ConnectionString = "Persist Security Info=False;Integrated Security=True;Trusted_Connection=Yes;database=BizAimsPro2008;server=Server-2k3s" BuildConnection =
[code]....
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May 17, 2012
I am connecting to a data stream that pushes data continuously and when I tried to set up a network stream I just could not connect and kept getting the 'not found' error. I used the httpwebrequest with webrequest.keepalive = true and started to consume the data by reading into a buffer and then appending to a stringbuilder. Once the stringbuilder reaches max size I flush it to a text file. The problem is that I get disconnected from the data stream because I am not reading the data fast enough. I need to keep the connection open and read the data while ensuring data gets stored in text files. If I use method "CONNECT" it does not connect to the stream.
While (True)
webrequest = DirectCast(Net.WebRequest.Create(url), HttpWebRequest)
webrequest.Credentials = New System.Net.NetworkCredential(username, password)
webrequest.Method = "GET"
[code]....
should I increase the buffer size and if so what is the max? that would mean I can read more data at a time and keep up with incoming push. Disparate here.
ACtually also I noticed that it gets stuck on this line
numbytesread = responseStream.Read(bufferread, 0, BUFFER_SIZE)
and then eventually I get disconnected.
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May 17, 2012
I am connecting to a data stream that pushes data continuously and when I tried to set up a network stream I just could not connect and kept getting the 'not found' error. I used the httpwebrequest with webrequest.keepalive = true and started to consume the data by reading into a buffer and then appending to a stringbuilder. Once the stringbuilder reaches max size I flush it to a text file. The problem is that I get disconnected from the data stream because I am not reading the data fast enough. I need to keep the connection open and read the data while ensuring data gets stored in text files.If I use method "CONNECT" it does not connect to the stream.[code]
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Sep 3, 2011
I understand the possibilities for encrypting a connection string in .net v4. I have a win forms application that will be used by multiple people on different machines. I understand that I need to protect the connection string at time of the app being first run on the target machine. However I am concerned that for a period of time my connection string will be unencrypted. I am looking for advice in how to deploy my app with the connection string already encrypted or encrypted during installation. encrypting the connection string in a secure way?
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Dec 19, 2011
Try If functionmode = "ADD" Then
[Code]...
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Jul 5, 2011
I got this error..The connection was not closed. The connection's current state is open.
This is coding to add data in Ms access in vb...
Imports System.Data.OleDb Public Class Form1
[Code]...
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May 20, 2010
I'm developing a device app in VB.net that will access a SQL Server database. I need to establish a connection when the app is launched, and keep the connection open until the app is closed. I've done the following:In the Master Module:
Public CNN
As SqlConnection
In the Main menu form load:
CNN =
New SqlConnection(sqlConnString)
CNN.Open()
Then when I want to read from the database:
Dim sqlDR
As SqlDataReader
SQL = "SELECT Name FROM Table"
[code]....
When I run the same code without the global CNN, but rather dim the connection inside the Select function, all works well.
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Jan 19, 2011
I'm developing an app in vb.net (visual studio 2008). I have a Teradata back-end that will be supporting multiple users in a production environment. I need to use variables in the connection string as the user/pass will be changed every 3 months.
For the gist of the application:
In it's most basic form - I have a search form which works correctly - it pulls results into a listbox and the user then double clicks the list box which will then open a form that is bound via table adapter to the back-end table (Teradata). My connection string is fine everywhere in the application. My problem is using a modified connection string for the "fill" function of the table adapter once the form is opened.
I'm using the code below for the on-load event and keep getting an "invalid connection string" - again, the connection string works fine everywhere else in the app, and the variables etc... are working correctly.
Private Sub adaptertest_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim DBConnStr As String = "Provider=TDOLEDB;Data Source=TDDEV;Persist Security
[Code].....
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Aug 26, 2009
I'm facing a problem after installation any software setup that has a database in access(mdb file) How to I transfer file path in our connection string.
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Mar 11, 2010
I'm trying to insert a new records into database, one of those records is a "datetime"...when I type a wrong date, and try to insert those values into database, i get an error (about wrong typed date etc.)...ok, that's fine, things need to work that way. But here comes the problem, I correct the date, and then try to insert values again...here I get an error from the post title. And this doesn't work until I close that form and run it again...here's part of my code:
Dim cvLicence As New SQL
Try
cvLicence.upis("INSERT INTO blabla (itsnotimportant) VALUES ('something')")
MsgBox("everything's fine", MsgBoxStyle.Information)
[code]....
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Jun 12, 2011
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
exitwithout()
[code].....
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Sep 7, 2011
When it comes to database connections what is the difference between closing a connection & disposing a connection? I'm hoping to gain a more technical understanding of what happens when each is called & the effect on the database.
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Mar 18, 2012
I am trying to connect DSN from my VB 2008 project. When i try using myoledb.connectionstring="DSN=myDNSname" I get the following error message An OLEDB provider was not specified in the connectionstring.
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Nov 9, 2009
i want to ask what is the difference between oledb connection and odbc connection. I have a case, my office used ncomputing then i have to developed an application using sqlserver 2000 and vb.net 2005, i used oledb connection. When i try to implement it in ncomputing, why user must has admin access level and dbo level in sql server, it seems trouble when all users are admin. But there's a rumor that when using odbc connection, we dont need to give admin access level for users.es.
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May 14, 2010
This will happen at random, and I can always just catch the error and re-establish connection to the server, but I am confused as to why. When doing lots of inserting into the sql server, I only establish one connection that is public, instead of many little connections. I had my doubts on a public sql connection, but it's been running great, and I've seen no problems until this morning. Again, this random moment I hit an error that stated, sql connection state is broken. Is it bad practice to just accept this error, and when it happens, re-establish the connection?
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