I have a Delphi-based client-server application. The server is a fairly simple application with a TRemoteDataModule. The client application connects to it via a TSocketConnection.
Everything is working fine on that front.
Is there a way to access the list of currently active connections for the TRemoteDataModule?
The reason I'm asking is because I would like to prevent users from connecting from more than one machine at a time to the same server, so I figured I would keep a list of usernames per connection and check against it whenever a new connection is attempted, or beforehand, client-side, via a a COM function.
Or should I be using some other mechanism altogether?
As an aside, is there a way to see which threading model and instancing model were used when creating the RDM? I'm not the one who created it, and I don't know where to find that.
Cheers!
Using Delphi XE5, if that makes a difference
Related
I am planning to create a desktop app (Java or C# WPF) which would be used by multiple users. The requirements are such that a Graph DB like Neo4j fits perfectly into the scheme of things. I have done some investigations and it looks really good. I am working on the community edition. Now here is the problem. From what I have observed, I am able to make only one connection to the database. The moment I try to make a connection from another instance I get an error. Even accessing on localhost:7474 gives an error.
Is this by design? I understand that in a web App, I can still use a static reference to a single DB instance and work with it. But in a desktop app scenario how do I ensure that multiple users are able to access the database from their apps?
Your app instances can access the same neo4j server through its REST API. There is no need to directly connect to the DB.
Here is a page that shows you how to do that in Java.
This is more of an architectural question rather than anything code-related. I'm working on a project to auto-create invoices in QuickBooks using data from our ERP, in order to speed up the process of adding that data. It seems that it is a requirement that in order to access data within the QuickBooks company file directly, you need to use the SDK (which actually opens the file using a QuickBooks application instance). Since my application will need to access two company files depending on where the request came from, I can't keep it open, and this opening/closing adds 15ish seconds to each request.
Why is this a requirement, does anyone know? Is there another way to directly access the data and bypass the massive overhead of the QuickBooks application?
Thanks!
Why is this a requirement, does anyone know?
My understanding (based on a really old forum post by an Intuit developer) is that the way the SDK works is by using a GUI message pump Windows COM call to push data to QuickBooks.
No GUI present = no message pump = no connection to QuickBooks. Thus, you need the GUI components of QB in place.
Is there another way to directly access the data and bypass the massive overhead of the QuickBooks application?
No.
If it's a problem, consider batching your requests, queueing them up, and sending more than one at a time in a batch. This is what the Web Connector (and most other QuickBooks integrated apps) do to avoid this issue. It's very, very rare that an application truly needs real-time connections to QuickBooks (and be careful if you think you do - QuickBooks is not a great candidate for real-time access to data - there's a lot of things that can lock you out of QuickBooks so you have to be careful if you're building an app that assumes you'll always be able to connect to it).
I'm searching for information on database connectivity (Firebird in my case) with IntraWeb Applications.
I especially need to know the difference(s) involved in using the database on the TDataModule with LockDataModule function, or using the database on the UserSessionUnit.
For example i need to have the database totally disconnected if no users are using the server, and at most 30 users will be connected.
I may at worst have to connect to some old paradox Database and i need a structure that could handle that (i know that i'll have to generate a folder based on WebApplication.AppID to handle sessions). At worst...
Thanks in advance for any piece of information or useful links you could provide me ^^
Scenario 1 - You leave "Pool Data Connections" unchecked in the Intraweb Application Wizard
In this scenario the wizard creates a ServerController, a UserSession but not a DataModule. You place your database, session and dataset components on the UserSession.
Whenever a new user connects to your website a new instance of the UserSession is created and a connection to the database is made. When the ServerController.SessionTimeOut expires due to user inactivity the UserSession is destroyed and that particular connection to the database is severed.
For 30 concurrent users this model will probably be fine for you and should guarantee that all database connections will be severed when the website is not in use.
Scenario 2 - You check "Pool Data Connections" in the Intraweb Application Wizard
As well as the ServerController and the UserSession the wizard will create an empty DataModule. You place your database, session and dataset components on the DataModule.
The ServerModule has a TIWDataModulePool component on it which has PoolCount property.
When your application starts it creates PoolCount instances of the DataModule each one of which makes a connection to the database. As your pages require database access they call LockDataModule and UnlockDataModule to temporarily make use of one of the DataModule instances from the pool.
When your application closes the DataModule instances in the pool are destroyed and their connections to the database are closed.
This model is appropriate when having an open database connection per user would exceed the capabilities of your database server. For just 30 users connecting to a FireBird database I don't believe it would be required.
You may want to consider using a component set like kbmMW by http://www.components4programmers.com/ I have used this for years with Desktop apps ans now with IW apps. I deploy my apps as Services and currently having a few issues deploying as an ISAPI. kbmMW is well suited for an app with lots of connections as it offers connection pooling etc... It has many features and benefits. Check out site for yourself.
I use the Enterprise version, though I think the free version may be useful to you.
Cheers!
-Lou
I have an existing complex website built using ASP.NET MVC, including a database backend, data layer, as well as the Web UI layer. Rebuilding this website in another language is not a feasible option.
There are some UI elements on some views (client side) which would benefit from live interactivity, involving both push and pull, so rather than implement some kind of custom long polling or websocket server in asp.net, I am looking to leverage node.js for Windows, and Socket.io.
My problem is that I need two way communication between both applications. Each user should only be able to receive data once they are authorised on the ASP.NET website, so I first need communication for this. Secondly, once certain events occur on the ASP.NET website I want to immediately push this data to the Node server, to be broadcast to specific users or groups of users. Thirdly, I would like any data sent to the node.js server to be pushed to the ASP.NET website for processing, as this is where all our business logic lies. The sole reason for adding Node.js is to have the possibility to push data directly to the client, I do not want to build any business logic into it (or as little as possible).
I would like to know what the fastest method of two-way push communication is between Node.Js and ASP.NET. The only good option I'm aware of so far is to create a special listener on a specific port on the node.js server and connect to that, but I was wondering if there's a more elegant or more efficient method? I also know that you could use a database inbetween but surely this would need to be polled and would be less efficient? Both servers will be running on the same server under a Visual Studio project.
Many thanks for any help you can provide.
I'm not an ASP.NET expert, but I think there are multiple ways you can achieve this:
1) As you said, you could make Node listen on a specific port for data and then react based on the data received (TCP)
2) You can make POST requests to Node.js (HTTP) and also send an auth-key in the process to be extra-secure. Like on 1) Node would react to the data you send.
3) Use something like Redis for pub-sub, send messages from ASP.NET (pub) and get them on the Node.js part (sub). This is even better if you want to scale your app across multiple machines etc.
The only good option I'm aware of so far is to create a special
listener on a specific port on the node.js server and connect to that,
but I was wondering if there's a more elegant or more efficient
method?
You can try to look at redis pub/sub model where ASP.NET MVC application and node.js would communicate through separate channels in order to achieve full-duplex communication. Or you can also try to use CouchDB change nofitications.
I also know that you could use a database inbetween but surely this
would need to be polled and would be less efficient?
Former techniques do not require you to poll for changes, but instead they will notify you when the changes happens or channel message arrives.
I hate to re-invent the wheel so I'm looking for an existing solution to create a simple authentication system for my application. I've experimented for a while with using CardSpace or OpenID inside the application but I can't convince management that these would be working solutions.
Of course, I could just build a simple login dialog where username, domain and (hashed) password is stored inside a database table and I've done such a thing many times already. I hate this solution since I feel it's just a weak option. And I don't want to spend too much time trying to make the whole logon system as secure as possible, especially since I suspect that there should be existing solutions for this.
So, next to OpenID/OpenAuth and CardSpace, are there any other Authentication solutions that can be used from a Delphi/WIN32 application?
Right now, the application will be used by many customers. Most are single-user environments, although it's likely that some of those will start to have two to 5 users once this authentication system is added. But we want to support a customer who needs to allow about 500 different users on the same application. These are spread over about 100 offices but they all connect to the same SQL Server database. (MS Access right now, but we're making it possible for this user to use SQL Server instead.) To make matters even more interesting, the customer uses Citrix to centralize the user systems and the application has straight access to the SQL Server database. It's not an ideal setup but then again, the customer isn't really paying for this. We're just setting up a test environment. A proof-of-concept which the customer will test for us. Flaws will be solved later on. But right now I need quick solutions and one of them is a practical authentication system where I don't have to write a lot of code.
Have you considered using SQL Server authentication and not allowing authentication for those using an Access Database?
If you use the new SQL Server Native Client and SQL Server 2005 you can have passwords expire and change them from your client application. All of the tools to create and manage user accounts are built into SQL Server Management Studio. And if you decide later to support Windows Authentication you just need to modify your connection string.
We have a system where users on the network use Windows Authentication so they don't need to worry about another user name and password. For users that access the system via a VPN and non-domain joined machines they use SQL Authentication.
Here is the MSDN Page that talks about dealing with passwords programmatically in SQL Server 2005
You do need to make sure that SQL Server Native Client is installed, but that is simple compared to the rest of ADO.
I would suggest then
Delphi - since you are using Delphi :)
Open source - since you need to be able to figure out what is wrong if there is a problem, you probably want it cheap.
So, here are some solutions:
http://www.torry.net/pages.php?id=313
CoWindowsAccount v.1.0
SSecurity v.1.2.1.3
http://free-password-manager-plus.software.informer.com/1.6/
It might work for your purposes, but why not ask Windows for the current domain and user name, and use them as unique IDs. Windows has already done the authentication, and it saves the users making up new passwords or anything. I've used this to good effect. I also made it optional to include the machine name in the ID, so that the same user on different computers would also be unique.