I'm using a SQL database and I'm writing a VB.NET client application. This application is used on multiple computers at the same time. If one of the clients makes an update to the database I would like to have the other clients to be aware of the update.
Has ony one already done this before?
I am converting an application to work with SQL.I need the application to monitor a specific table, so it can instantly pick up on changes.The sql server database is on the same machine.The table it needs to monitor is called MaintenanceRecords and it is inserted into via web service.I need to display a message in my VB project when an insert occurs in MaintenanceRecords table.
View 2 RepliesSince ADO.Net uses a 'disconnected' model where the data available to a single program is just a copy of what is in the database, what is the normal way to handle multiple programs needing to update the same table in a database? The problem I see is that a program can't update unless his copy of the data is the most up-to-date. Are we supposed to read before updating and hope that the update occurs before someone else changes the data?
View 2 RepliesI have a machine which creates a new log file at the beginning of the day(12am) and updates the log file whenever there is any changes until the end of the day. How do I import the data in real time (30 sec, 1min or whenever there is any changes) to my SQL server database? Will SQL Server 2008 be able to access the active log file? If not will it be easier if I let my machine create a new log file whenever there is any updates? But if it is so, how do I import so many log files with different names in real time. (I must be able to scale the solution up to multiple machines).
View 3 RepliesI am designing a fairly small application to manage a waiting area for a clinical department. There will be a receptionist who books appointments and updates exisiting appointments to say that a patient has "Arrived". In seperate rooms will be nurses who call patients who have "Arrived" and update the appointment as "In Session" and finally as "Discharged". The appointments are viewed in a flexgrid with nurses across the top and time down the left, patient names are displayed at the relevant times and the cells are shaded a colour to represent the current appointment status ("Booked", "Arrived", "In Session" and "Discharged").
I am using SQL Server as the back-end and Visual Basic 6 (I know) as my front-end.I have been told that there will be 2 or 3 nurses plus the receptionist logged in to the system but I would like to cater for growth.My question is what is the best mechanism to use in order to reflect the status change made by one user on the screens of the other users currently logged in?
I have been thinking about using a timer to refresh the data at a set interval but I do not want to keep hitting the server excessively (although what is considered excessive? we would be talking about a call for data every 60 secs per user). Plus the server could be serving data for many other applications so this is another consideration.Alternatively I have been thinking about sending some kind of message via Winsock to the other users notifying them of data changes as they happen. I don't have a lot of experience with this and am concerned about clients not receiving messages and users seeing old data. It also seems strange to me that once the days appointments have been retrieved from the database that "in theory" a client could go the whole day without having to query the database again to pick up changes - kind of scary.Some information on the data:We would probably be looking at around 100 appointments per day We capture patient name, date of birth, date and time of appointment and appointment status.What is the standard approach / best practice for this kind of scenario?
I have been struggling to find a solution for this problem. What I need to do is build a server application that accepts tcp client requests from different clients running on same port say:1003. I experimented by using asynchronous mode call backs etc. but it disconnects once connection is established and does not respond for further requests from the same client.
View 1 RepliesXML is used as one of our main integration points. it comes over by many clients at a time but too many clients importing at the same time can slow down our database to a crawl. Someone has to have solved a problem like this. I am basically using VB to parse through the data and import what i want and don't want.
View 2 Repliesi want to designe a simple program that have one server and multiple clients.i program with vb.net,but dont know anything about winsock, can you send me a sample code for start.
View 1 RepliesI have been programming a TcpListener Program and I have everything working right! So far... Except that when I have multiple clients connecting to my Server... I used a try catch statement to catch the error and it says that tcplistener doesn't allow multi connections... think creating a new thread for each connection sounds like the most reasonible answer but I can't grasp the concept of it...
Here is my frmMain:
Imports System.IO
Imports System.Net
[code].....
I have a ASP.Net VB.Net application, which I developed an deployed in about 2004. I have just upgraded it to a new server and IIS 6.0. The application requires users to login from IE it and maintains their State using sessions on the server. I would like the users to be able to have multiple browsers open, each running with unique data on their client system. Is this possible, if so, what do I need to do?
View 4 Repliesl have just written a vb.net application and would like to install it on the server such that various users would access the central database on the server how would l achieve that in vb.net
View 1 RepliesI teach programming at a high school and I have used VB 2005 Express (in a computer lab of 33 clients) for a number of years without a problem. However, this year I switched over to VB 2008 Express and now I am constantly having registration issues. I have found the following ...
1. You must re-register the product for every user on that client
2. Each client must have a unique registration key
3. You are allowed only 30 days of useage without registration
What is happening is I asked my students to register the application themselves. But we keep getting this registration request every time a student switches seats in the room. Now we are getting an error message that says we have had too many registrations from this IP address.Is there a registration key that will work on more than one computer? Is there any way around the registration issue?
I'm new to network programming and i'm trying to write a server that can communicate with multiple clients through tcp/ip, the clients need to communicate with the server to and with the other clients. Currently i've got a client server program that works fine for only one client:
[Code]...
I'll guess to accept multiple clients i have to create some clienthandler class at server side, but i have no idea which code it has to contain, i've already spend hours searching on google but didn't find anything usefull. Can somebody help me with this ?
I am facing a problem in VB .net Client/Server application where I am successfully able to talk between them using TCPListener and TCPClient class usage. However, when I try to connect another Client to the same server on the same welcome port, it errors out throwing an exception or behaves very unexpectedly.Isn't it true that the Server connection is on a WELCOME PORT for all the clients, and that each client connected gets a new port to carry on its communication with the server AUTOMATICALLY (according to the Tomcat webserver working)
View 2 RepliesI made a simple chat system that connects to a server with a client one on one. I'm not really sure how to get multiple clients with the server so that you can see everyone's messages. Here is the source code. The Server only accepts one client at a time.
View 3 RepliesHow can I make a server application? How can I then create another application that is meant for the clients!? I have tried to look for something for over 3 months now. All that stuff about TCP/IP just is not working! Using TCP/IP I cannot connect to anyone out of my network! How can I make it so when you start the client application it will automatically connect you to the server. Then having 2 textbox's and one button that says "Send". One text box will have what has been send and recived and the other textbox will be what you type to then later send it! How can I make it work with up to five clients!?
View 4 RepliesI have a large class that I built to act as a TCP server for one of my silverlight applications. When a user connects it stores the tcp client into a table for later communication. The problem is that when I send data, with more than one client connected, it loops through both open TCP Clients but some how sends the data twice to the same client.... the other tcp client never receives his data. This isn't a logic issue as I can step through the code and see that it is clearly taking each individual TCP client out of the table and sending it the data. They all use the same port... could that be the issue? And if so how do I make it so that it can connect on one port then transfer to another? I have tried using different computers for connecting but still the most recently connected client receives all of the packets of data.
View 6 Repliesam working on an application in vb that requires using shell to call up windows date and time settings from clients machine.
View 2 RepliesI am developing project on cyber cafe using vb .net 2005 and winsock i don't know how to accept connections from multiple clients to a server having winsock control
View 2 RepliesI have a program that uses sql for the database. The issue im having is when two users attempt to update the same record then the update from second user overwrites the record from the first user. I believe this problem comes from the the way i attempt to preserve existing text in the fields.
My thought on whats going on is: If the form has fields A and B. Both users start with a blank form. User 1 adds a record with an entry in field A. When user 2 goes to update the record with an entry in form B, the program overwrites user 1s field A entry with the blank field A from user 2.
Is there a way to force it to grab the most recent data before it tries to add/update? I thought about resetting the digit combo box to the same digit which would trigger the change event for that field. but the issue with that is it would also wipe out the current entries on the form.
Below is the change event for the digit combobox, the main submit procedure, and the subprocedure for one of the days.
[code]
Private Sub cboDigit_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cboDigit.SelectedIndexChanged, cboOffice.SelectedIndexChanged, dtEndDate.ValueChanged, dtStartDate.ValueChanged
[Code].....
Before performing an update, the application must search for that record in the database. Once it's found then it return to the Data access layer. Typicaly when i return rows i return them in a dataset. The i send it to the client to load on to the ListView Constrol or to textbooxes. therefore data was sent from the dataset object, therefore onces the user has made updates to the data, first i must update the dataset.
In the Data access layer i can write method that contains the command object for update DB and bind it with the current Dataset so that each time dataset updates it sychrinizes DB with it. Assume i have a method called update() in teh business layer that calls the updateDB in the DataAccess Layer, how can i call the Update() of the business layer each time the user updates the dataset?
Is there any open-source component for VB.NET that offers real-time spelling (i.e., as you type) much like word? I found some free and open source components but without that ability.
View 2 RepliesIn grid there r checkboxes for selecting the records to be updated as soon as checkbox is checked textboxes changes to edit mode. when data is modified and update button is clicked updation should be done to the database.But when update button is clicked its not working.when i checked through breakpoints i m not getting the value for the variable strID.
Protected Sub btnupdate_Click( ByVal sender As Object , ByVal e As System.EventArgs) Handles btnupdate.Click
Dim strSql As New StringBuilder( String .Empty)
Dim cmdup As New SqlCommand
For i As Integer = 0 To GridView1.Rows.Count - 1
[code].....
it is possible to do a multiple records editing by linqtosql method in one click event?What I've been trying to do is to edit all the names in the table which are having the same account number.
Private Sub Button2_Click(------------) Handles Button2.Click
Dim accnt As String
accnt = Textbox1.Text
Dim db As New memrecDataContext()
[code]....
Why is it these codes could only edit records in one datarow?Can you debug the codes to edit all records which are having the same account number after it is being query?
How can I display a running stopwatch on my form? I am creating a timer but I do not want to use the timer class.
View 4 RepliesI making a simple online chat using an ftp server by downloading and uploading text. I use a thread to update the chat log continuously. But it doesn't update in real time. Is there a way to create a server that clients can upload to and download from extremely quickly? How do programs like MSN messenger or better online multiplayer games do it?
View 1 RepliesWhat would be the proper way to get the cursor position while the mousebutton is held down? I've tried using a do while loop with a background worker, but it freezes up the application.
View 1 RepliesI'm working on a windows forms application (.NET 4.0).My form contains a 'Fast Line' chart using the Microsoft chart control included in VS2010.The chart gets filled with about 20,000 datapoints.My application then starts receiving market data from a server via DDE (Dynamic Data Exchange) in real-time and adds it the chart.
View 5 RepliesI have to send a sequence of video frames over UDP as fast and real-time as possible and while I got the basics working, I am running into all sorts of difficulties. Some of my goals:Data will normally be sent over dial-up (hence UDP instead of TCP), but also needs to support fast Ethernet.It's OK to occasionally drop frames (hence UDP instead of TCP).Need low latency. The frame the remote receives should be one that was recently sent (no more than a few frames waiting in buffers).I need to be able to detect the effective bandwidth so that I can compress the frames more or less to keep frame rate up.I break up frame data into one or more datagrams of about 500 bytes and each has a sequence number and other info. The receiver reassembles the entire frame and detects if any datagrams are missing.If the receiver detects more than a certain percentage of dropped frames (e.g. 50% over the last 10 frames), I send a TCP message to the sender to slow down by 50%. Sender than slowly increases speed by 5% each subsequent frame.Using System.Net.Sockets.UdpClient to send and receive the data.I have a separate TCP channel used for control messages back to sender.My main difficulty right now is detecting the effective bandwidth and dealing with latency, especially over dial-up (max ~4,000 bytes/sec). For example, if I try to send 100,000 bytes/second using TcpClient.Send() they ALL seem to arrive (no dropped datagrams) but with large latency by the time last datagram arrives. I think the TcpClient.Send() function is blocking until the buffer is able to send which messes up my current algorithm.
Can anybody point me to any sources of information for how to:Detect actual bandwidth over UDP.A better algorithm for dynamically adjusting bandwidth to suit the available pipe.Send data smoothly at the desired bandwidth.A way to detect and keep latency down to a minimum.I have been spinning my wheels over the last week and every time I solve one problem it seems another rears up is head.
Make real time chart?
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