I am developing OPC Client in windows C#. I have developed the code and reading
OPC Items on Sampling as well as event based (OnDataChange). When I am
working with local machine then my code works fine with both Sampling as well
as OnDataChange, but when I am trying to read data from Remote OPC Server
then Sampling works fine but I am not able fetch data on event based process.
I am able to connect to the OPC Server but when i am adding subscription to
it then i am getting error.
HRESULT : 0x80040202.
group1.DataChanged += new DataChangeEventHandler(this.DataChangeHandler);
group1.AdviseIOPCDataCallback();//exception HRESULT : 0x80040202.
OPC server connected & then register the group also but i got the exception when reading data.
The issue usually is that when you use Advise(), the server will make a DCOM connection back to the client (standard DCOM connection points). The client needs to be set up properly to allow this to happen (i.e. the right security settings to allow the server to execute code on the client).
You should read this page: http://www.softwaretoolbox.com/xpsp2/, it covers a lot of recommendations on how to set up DCOM properly for OPC usage. There are a lot of security concerns here. The Software Toolbox site has a lot of great information (and videos too). If you are still having trouble getting it to work, I recommend investing in an OPC tunneling product that will allow you to do remote OPC without having to jump through all the DCOM loops.
You don't have to be using OPCDA.NET to have the same issue. You can use any OPC client and get it working first with your remote server, then focus on figuring out how to get it all hooked up in OPCDA.NET. I recommend OPC Quick Client (comes with Software Toolbox TOP Server demo).
The problem you are actually having is with the callback. In other words, it isn't the advise call that is failing you, it is the callback from the OPC server (which advise triggers). This error is usually caused by user authentication problems (i.e. the user accounts do not match on both computers). Check out the OPC server's user account on the remote computer. If it doesn't exist on your local computer, you found the problem!
There is an automated application to help you figure out your problem. I recommend you download OPC Expert (Google it). It is a free application, does not require installation, and does not change Windows Registry. It has saved me many times. Also, the vendor (OPCTI) is extremely helpful, so check them out.
That problem is because when you connect to the server, you might use the first connect function, which is server.connect();
Instead, try:
server.connect(new Opc.ConnectData(new System.Net.NetworkCredential()));
This works for me. Hope it helps:)
Related
I'm facing a task which is to extract historical data from an OPC system, and then store these data into a standalone database for our BI team.
Although I'm a experienced developer, but I never use OPC UA before. I found the latest library provided by OPC Foundation here:
https://github.com/OPCFoundation/UA-.NETStandardLibrary
There is a sample console client app in this repo. However, I didn't find any clue for HDA (Historical Data Access). So, could anyone help out?
Also, I'm actually the only IT background person in my company. The manager told me that there is another guy who is maintaining the OPC system using some 3rd party application, so that I assume that it is not necessary to implement anything about the OPC server. In other words, I suppose I just need to implement an OPC client connecting to some URLs which can be found in that OPC application. Does my assumption correct?
To sum up, there are two questions:
How to implement an OPC UA Client to extract historical data with OPC UA-.NETStandardLibrary
Given that the current OPC system is running on top of a 3rd party application, does that mean I don't need to code anything about the "Server"?
Any help will be appreciated.
Unless you actually need to support .NET Standard, you should rather be looking at a different GitHub project: https://github.com/OPCFoundation/UA-.NET . Under SampleApplications/Samples/HistoryClient you should find what you need.
And yes, if the OPC UA server is in place, configured and running, your development task should be just to write an OPC UA client. You need to "know" about what data the server presents to you through OPC (or browse for it from the code), but you need not to know about the internal implementation of the server (its code).
I would appreciate if someone could help.
I have written a Client/Server Sockets application. The client is Windows Forms C# app and the server is a C# console app which runs locally. The client application has a login form containing the field with generated port.
When user logins he is connecting to the server using that port and the server continues listening incoming connections.
Everything works fine when I test my application simply running several instances of Visual Studio project on one PC. Now, I would like to test it on several PCs and I am very confused here.
I would be grateful if someone could explain in simle words how to run my app on two machines.
How do both users connect to the same server? Where should it be located? Should the server have one IP and different ports per one users group?
Also, my application uses SQL Server Database which is installed locally on one PC. So the application uses connection string with that PC Name. In case of two PCs is it possible to connect the second computer to DB on first PC?
I am sorry if this sounds silly :)
Thanks a lot
So if I am correct you are wondering the following three things?
Q1. How do I test my software in a multiple machine environment.
A: This is perhaps not really a Stackoverflow question but what I would do in this case is to have a small setup in Hyper-V with several machines with different operating systems that all have a shared folder that I can deploy my code to. Of course for more extended testing you would need to get more machines and copy the executables to that machine for testing for the first stage and perhaps write a setup software for the second stage of testing, but that depends on the how much testing you actually do.
Q2. How to I allow several users to connect to my service?
A: I think that Anthony Horne has a great answer to this in the comments - Tell your service to listen on port X and when a client tries to connect open a new communication instance on port Y and ask the client to call back to that port. This is as far as I know industry standard for solving this type of problem.
Q3. My application uses a SQL Server Database can I allow clients to connect to it remotely.
A: Yes you can. Please see this Stackoverflow question.
We are planning on implementing our new software application as shown below.
Does this architecture look fit for purpose?
Items to Note:
There are many PC's
The pc has a WCF client as it needs to upload data to the
database periodically.
The PC has a server because the end user on the terminal server needs
to be able to interrogate the pc for information
The terminal server is the GUI for users so they can remotely connect
to a specific PC to interrogate the pc for information
We are using basicHttpBinding below
What else have we considered?
We have tried WCF NetPeerTcpBinding (i.e P2P) but it does not support
request-reply operations.
We have tried WCF Duplex but with the requirements listed above in the items to note section we would end up with a client and server at both ends anyway.
Well I apologize but I basically disagree with your architecture.
WCF is not designed or suited for anything other than a request-response communication.
Its full duplex ability will not enable your server side to issue communication to a specific client unless that client already issued a connection to the server.
That means that in order to achieve a prestigious online full duplex communication with all your clients - all your clients must maintain an open port to the server.
Having a dual client and server per PC in order to achieve an online full duplex is a step forward as it will solve the issue of keeping a port open per client however it has downsides in terms of security as it means that the specific PC is open to receive multiple connection requests. Another issue can occur with deadly reentrancies if you not careful. So, basically you will be saving 'ports' in exchange for architecture
maintainability and fitness to your solution.
So if you are targeting a deployment of around 200-300 PC's your architecture will hold but if you are targeting a larger deployment of thousands of PC's - it will not hold.
I am just learning c#, and am programming a Windows client that collects temperature data from the computer and needs to send it to a remote linux mySQL Database.
I was going to program it directly in the c# client, but I want to learn more ways to do this and gain experience. And programming it directly would be less secure and most likely require an extra connector.
Can any of you advise me of other ways, or ways you would do this?
Any way to program a C# program that acts as a web-service on my linux mySQL Server? Where should I look/search to learn more about this. Is it called something special? Or maybe its not done in C#?
Should I program a php script that accepts HTTP SEND/GET requests from my C# Desktop client?
Any other way?
What way is most 'professional' in the real world? Trying to learn on my own! :D
FORMAT:
Windows Desktop: client programmed in C# That retrieves temp data and needs to send to server
Linux Server: Runs Apache and mySQL Server with a database already setup. Closed to outside Connections
My advice is to set up a web service to communicate with your windows client. Directly connecting to mysql server is ok if they both resident in a same lan, but if not, for example your windows client is running on some laptop travelling everywhere or even the mysql server permits local incoming connection only, your should set up a web service. Also the http connection can usually go through firewalls while connections over other ports are blocked.
php is a good way to do this. Since you are learning c#, you may want to use c# to do the server side programming as well, so why not give a try of mono?
Directly exposing a MySQL Server to the internet is strongly dicouraged, Additionally this gives you a rather coarse-grained set of access rights, that might not be enough for your application, so running some sort of server app is the right way to go.
With mono you can run a lot of .Net (and thus C#) based code on a Linux server just fine. Rule of thumb is: If it doesn't have a Winforms GUI and no P/Invoke it will work just fine. Ofcourse this needs mono on the server, which is not given on most commercial hosts.
Running the server in PHP makes it a lot more portable, but has a performance overhead. Additionally it doesn't allow for some of your busines logic objects to be implemented in a DLL assembly and used on both sides.
As for the protocol: Chose your poison. Rule of thumb again is, that predefined protocols such as SOAP tend to need a bit more work (and more learning in the first go), but on the long term tend to be more robust.
For your special use-case I'd personally go with a quick PHP based solution where the protocol is just a simple GET with a few parameters, one being the temperature(s) and the others authenticating the client.
If the temperature sensor generates events, then I would 'push' the data from the Windows box to the Linux box - this will save the latter checking often and finding no updates. However if you are just taking temperature samples, I would 'pull' the data from the Linux machine. Either way, if you want to use HTTP you will need a web service on either side.
Alternatively, you could just connect to your MySQL database remotely from C#, and write the data directly (no web service would then be required). That might be the quickest way to get this working.
The 'which is professional' question is subjective - all three options above are fine. Just make the code clear and concise :)
I am writing you because of a new problem I need to solve, and I have now been banging my head against a wall for too long now.
Basically, I need to create an application that can take care of the following:
A user starts an app, which sends a broadcast to the subnet, and recieves a response of all servers there with their IP (and some additional info). The user can then select what server he wants to connect to.
Making it work is simple enough, with identifying the subnet, and broadcasting with UDP, and then having a different server application recieving it and sending back a response . The problem lies with these restrictions, that I need to take into consideration:
There will most likely also be clients on the server machines in the network, meaning that we can assume that the application is present on all machines. Every machine needs to have the listener running, and every machine can launch the GUI for selecting a server.
I am only allowed to add one exception to the firewall - an exception that handles both sending out the broadcasts, recieving broadcasts, sending answers and recieving answers.
I should also only be adding one Windows Service
on a server machine, the listener should run as a windows service, so the user won't notice it. Nor will the user notice, that the response is sent back to the client.
On the client machine, the user can start an application, which will notify the application to emmit the broadcast, and will get all the server responses, so the user can choose one to connect to.
Besides from the application that the user launches in order to select a server, there should be no interaction with the user whatsoever. Not even a popup, requesting the user to allow traffic trough the firewall - it should all be automatically
It needs to work on and in between Win XP, Win Vista and Win 7.
I don't know if I am putting too many constrains on myself, but I really hope that I can make the application with these requirements.
I have a few ideas - I just need to figure out how to do it:
Should i make everything into one application, that I add to the firewall exception list, so it will take care of the traffic on both the server and the client machines?
Should I add a custom exception to the firewall, allowing UDP traffic on a specific port, and then have all traffic flow trough that?
Is there a third and better option for managing that?
It is OK to have the service running on both client and server machines. But can it take care of everything for me - like it handling both the broadcast send/recieve and answer send/recieve? And is there any way to extract the information about servers on the network from a service?
I know it is a lot, but I really hope that you will be able to help me out.
let me know if I wasn't clear enough, or if you need further explanations.
I am coding in C# .Net, and I can utilize all I want from the .Net framework. As soon as I have this functionality implemented
All the best
/Sagi
The kind of peer-to-peer networking problems become simple to the point of being trivial if you designate one machine as the master server. It should have a well-known name that all sub-servers can connect to so they can publish (and withdraw) their availability. A client can then send a query request to the same server and get a list of known servers in return.
This can also solve your firewall problem, the master server could be listening on port 80.
Look into the System.Net.PeerToPeer namespace for a p2p solution supported by the framework.
Maybe a UPnP server and client may be a solution to your problem?