I did my best to search all topics regarding to SCADA and developing your own C++ desktop application to communicate with PLCs, but could not find any recent, or in my opinion, relevant topics that fit what I needed. If I missed them, a link to them would be very much appreciated. If I also happened to post this in the wrong section, or you can think of a better section for me to post this in, I will take it there.
With that said, I thank you in advance for taking the time to read my questions, and appreciate any input you have to offer.
A little bit about what I'm doing
I'm currently in school for electromechanical engineering, and for my final year project I am developing a desktop application in C++ to monitor PLCs we have located within one of our labs.
Within this lab, I have a pre-existing ethernet network connecting all PLCs to single point, which I am tying into with a PC, and will be doing all my work from there.
I will be developing the application in Qt for an easy way to design the GUI, and giving me access to the QNetworkInterface as well as QTcpSocket.
With that said, I wouldn't go as far as saying I'm an experienced programmer, but I have been fooling around with a few languages (i.e.: python, c++, c, php) for quite a few years, and am still learning, considering the learning NEVER stops.
My questions
Is there any reference material I can read, that you can suggest, on the subject to more easily understand what sort of process I need to go through to receive information (i.e.: individual I/Os, status bits, tags, logs, etc...) from the PLCs directly, and not through an OPC server?
If an OPC server is required, I've never dealt with OPC links other than using Rockwell Automations RSLinx to grab tags and display their values within excel (I had created a prototype using that exact method to start, but would like to move away from excel, and if possible, the OPC server (RSLinx) as well). What would you suggest to someone who knows nothing about the subject of OPC servers, or to my knowledge, OPC in general?
Have any of you previously written your own application to do something similar, if not of the same nature to what I'm trying to accomplish?
What advice or suggestions would you give for someone who is attempting this type of project?
PS: As a start for this project, I would initially just want to get the reading of the I/Os (tags or addresses) to view what their current values are (closed or open for inputs, energized or not for outputs). But eventually I would also like to be able to write values to tags on the PLCs I'm monitoring based on the values I've received from them.
PSS: I would like to note again, that I am still a student, and am still learning about this subject in it's entirety. I would just like to ask for your patience, as I may not grasp things completely the first time!
If I've missed any information you feel is pertinent to be able to provide an answer, please let me know! I will do my best to come up with said information in a timely manner!
Thank you!
EDIT #1: Added in another question, and altered my first question slightly
EDIT #2: Fixed up question 2
IMHO a SCADA program should have as a minimum requirement to be able to connect to an OPC server. OPC is used for most commercial PLCs.
Strictly speaking there is no need to have an OPC server/client approach but it gives you flexibility and gives you an abstraction model. If you want to directly connect to PLCs using a protocol then that is of course possible as well. You then need to know more details about the protocols and their various versions.
Yes I worked for a few years in a team that developed a commercial SCADA application.
It is very easy to get lost in details in such a project so try to keep things as simple as possible. By using OPC you will save time instead of fiddling directly with the protocols. You could add the ability to add custom-drivers for other protocols - depending on your timeframe. Try to model up your project before you start coding to a birdsview of the model and avoid getting lost in the details.
I would stay well away from looking to write your own code to connect directly
to an AB PLC - there are products out there that you can use in your application:
http://www.rtaautomation.com/software/ethernetip/client/tagc/ControlWin.html
http://www.automatedsolutions.com/products/dotnet/ascomm/
You would be better to use OPC - you can write you own OPC client if you want and follow examples you find here:
http://www.opcconnect.com/source.php#freesource
According to this http://www.control.com/thread/1026173407 you should be able to get source code of Kepwares OPC Quick Client.
It would probably be easier to just use a library as in this example (RSLogix,C#):
http://www.mesta-automation.com/opc-client-with-c-an-how-to-video/
You might find this of use:
http://www.rockwellautomation.co.kr/applications/gs/ap/GSKR.nsf/files/rslinxsdk_ma_eng.pdf/$file/rslinxsdk_ma_eng.pdf
Some resources:
http://www.opcconnect.com/ ,
http://www.mesta-automation.com/
Answer to question #4 - realize that your lab technically could contain ANY manufacturer's PLCs in the future. If you ever took a Data Communications class, you realize that for N different PLC types, you would have to write N different communication drivers for your PLC client.
This is where standards are helpful. Without the use of a standard protocol, scaling your lab could become more time consuming and less manageable. This is why communications standards exist.
HOWEVER, not all PLCs necessarily support the standard(s) you may decide upon.
The best choice is OPC/UA. Many PLCs have server drivers readily available. That means that your client just needs to understand 1 protocol (OPC/UA), and then it can "easily" be connected to any PLC that has a driver for that standard.
After that, there is OPC. After that, Modbus (TCP and RTU flavors), a relatively simple industry standard that is supported by most PLCs. EtherNet/IP is also a possible choice, although not all PLCs support it in a "server" role (many do support it as a client, but that is not what you need).
have a look at pycomm in github or pylogix at github which are Python written drivers to link to clx plc.
Related
I can't decide which way I should take so instead of trying all options I would like to get expert's or more knowlageable people's ideas since I'm a C++ newbie. (After frustration with php for years I understood C,C++ is the way to go )
Extra info: I'm only linux user for a year :)
--Here is what I want to do: Webapp that people can register and chat and be friends. Like facebookchat but no less ability than it (should be realtime all the way) (For instance: If a friend closes the browser it should be seem unavailable).
--Options I have I guess: Using boost:asio, using BSD directly, using opensource server like nginx,lighttpd with fcgi (I din't like libev, libevent.)
--Here is main questions:
1) Is Nginx+fcgi+CPP spawning a new Cpp programme for each request (Performance would be bad)
2) Would using a ready server+FCGI make it impossible or harder the chat thing i stated above.
3) Would you choose BSD, asio or tweaking a ready server for such thing?(with a short why)
(Scability for development is main concern. I mean if it requires new implementations it should be done in future)(blaa blaa must be done)
What would you do?
I think I'd step back a bit, and consider a few questions. First and foremost, it's not apparent from your question whether you're basically trying to set up a web site (or something on that order) that provides this service, or you want to write software that (or example) others could incorporate into their web sites.
Second, it's not entirely clear whether you're interested primarily in the client side, the server side, or both. Most of what you talk about is on the server side, but the features you talk about providing are mostly on the client side.
Third, is the question of whether you're willing to write a closed system that requires your client to work with your server, or you want to use something like XMPP to provide compatibility with existing software.
To summarize: you seem to be jumping directly into nitty-gritty details of how to do things; before you can figure out how very well, you first have to decide exactly what you're going to do. Until those are answered, many of the "how" questions can't be -- and after they're answered, many of the "how" questions may easily disappear.
I would start playing with Wt (http://www.webtoolkit.eu/wt) which is a framework for Web applications, or Qt (http://qt.nokia.com/products/) which offer good http and https support
How or what do I need to know programming wise in order to interact with the web using c++. For instance i want to wrote a program that automatically sends invites to players on yahoo chess. How would i go about doing this?
You'll need to understand the basics of TCP/IP and HTTP, possibly UDP, and the protocols involved with Yahoo's chess systems or posses a tool to work around them (A brief search leads me to believe there are few if any). You'll probably need a network API, I'd suggest looking at:
QtNetwork Module
Boost.Asio
Where Qt is easy to use, Asio is more powerful, and more 'C++' in nature. Qt has some nice webkit components, and I've used it to build a small web server, which was a lot of fun. You can accomplish quite a lot with it.
This page says they've added a captcha system to prevent certain people from interacting with their systems. I'm not familiar with Yahoo games and what the result of this has on what you'd want to do, however it suggests to me they'd rather you didn't write code to interact with their systems.
For this you need to use network APIs and use server side script like PHP/ASP to communicate with the web and C using message queue.
For some time now I've been tossing around what I think is am awesome idea: I want to write essentially a C++ phone server to handle all of my incoming calls on a land-line. I'll have a white-list (yay never having to worry about telemarketers ever again!), a black-list, and will be able to access my phone using my gaming headset, allowing me to make/answer calls while I'm gaming or whatever. In the future I'd also like to hook it up to a gui and make it have pop-ups and other cool features.
The problem is, I have no idea where to start. I'm familiar enough with C++, but have no idea how to go about doing anything with a phone-line. I can plug a phone-line into my computer, but I have no idea how to get my program to be able to use that connection. There's WinSock2 for being able to use my ethernet connection, is there something similar I'd be able to use to use the phone line? As it's using the same ethernet jack, I wonder if it's even possible to use WinSock2 to use the phone-line?
I saw this post, which wasn't particularly helpful: stackoverflow link , which points out Dual-tone multi-frequency signaling. I stumbled across this site: link, but isn't really going to help me get started.
So I was wondering, is there some sort of library out there that would allow me to tap into a phone-line that's connected to my computer? Is there a standard somewhere out there concerning phone-lines and what the different combinations of tone's mean? Can anyone here help get me started? I realize it's somewhat of a big undertaking, so any push in the right direction would be greatly appreciated. Thanks.
[Update:]
I found this question, which is a step in the right direction, but I'm not sure yet if it helps me (I need to go to bed, and will take a look at it in the morning). I did see mention of a Microsoft Telephony API though, I'll try doing more research on that tomorrow.
If working with MS products is not an absolute necessity, you might also consider taking a shot at Asterisk. This is an open-source PBX (in software) that allows development on Linux, Windows (emulated) and Mac. At the company where I work, we use it for implementing small-scale exchanges, about a 100 lines or so. It also interfaces well with VoIP and allows a whole host of protocols. I have developed scripts and programs in C++ that work on voice packets in real-time, and so far, my experience has been good. As for your stated use-case of blocking telemarketers etc., this would be a very good fit. Check out further details here.
After doing more research, having one link lead to another link, and coming up with new search terms, I stumbled across this site that looks like it could kick me off using the Windows Telephony API in C++: link. This link includes open source c++ samples showing how to do the basics of what this question asks, I'll just have to test to see if they actually still work.
This is only the beginning of my research, so I'll keep you posted on any other findings. If anyone else is knowledgeable in this area, please still feel free to drop me information on what I want to accomplish.
I got an assignment at work to create a system which will be able to direct sound to different output channels of our sound card. We are using M-Audio ProFire 610, which has 8 channel output and connects through FireWire. We are also using a Mac Mini as our host server and I'm gonna be working in Xcode.
This is the diagram of what I am building:
diagram http://img121.imageshack.us/img121/7865/diagramy.png
At first I thought that Java will be enough for this project, however later on I discovered that Java is not able to push sound to other than default output channels of the sound card so I decided to switch to C++. The problem is that I am a web developer and I don't have any experience in this language whatsoever - that is why I am looking for help from more experienced developers.
I found a Core Audio Primer for ios4 but not sure how much of it I can use for my project. I find it a bit confusing, too.
What steps should I take to complete this assignment? What frameworks should I use? Any code examples? I am looking for any help, hints, tips - well anything that will help me complete this project.
If you're just looking for audio pass-through, you might want to look at something that's already been built, like Jack which creates a software audio device that looks and works just like a real one (you can set it as default output for your app) and then allows you to route each channel anywhere you want (including to other applications).
If you want/need to make your own, definitely go with C++, for which there are many many tutorials (I learned from cplusplus.com). CoreAudio is the low-level C/C++ interface as Justin mentioned, but it's really hard to learn and use. A much simpler API is provided by PortAudio, for which I've worked a bit on the Mac implementation. Look at the tutorials there, make something similar for default input and output, and then to do the channel mapping use PaMacCore_SetupChannelMap, which is described here. You'll need to call it twice, once for the input stream and once for the output stream. Join the mailing list for PortAudio if you need more advice! Good luck!
the primary APIs are at CoreAudio/AudioHardware.h
most of the samples/supporting code provided by apple is in C++. however, the APIs are totally C (don't know if that helps you or not).
you'll want to access the Hardware Abstraction Layer (aka HAL), more details in this doc:
http://developer.apple.com/documentation/MusicAudio/Conceptual/CoreAudioOverview/CoreAudioOverview.pdf
for (a rather significant amount of) additional samples/usage, see $DEVELOPER_DIR/Extras/CoreAudio/
I need to start my new challenge, write my own RDP client for Linux (full protocol implementation based on 7.1). Most of you will suggest to search on the web for free RDP client....but in my case I have to write from scratch the application.
Is there anybody with RDP experience in C/C++ under Linux? I am not looking for technical information. At this stage I only need to evaluate how long it would take to write the application. I do not have any experiences with RDP. Roughly how long would it take for one person full time? There are many "variables" to consider....but just an estimation would be enough.
Thank you.
Luke
I have some experience because my company did some work with the RDP protocol. These are some select things you'll face should you go through it:
You'll have to work out different the compression algorithms. Mostly run-length encoding.
Encryption. The older versions of RDP used RC4 and RC5 if I recall correctly.
Authentication. NTLM and CredSSP are popular methods.
It would probably take you a month just to get something working assuming you'd write your client non-stop.
Also as Duck has pointed out in the comments there are many little things. Just for example: how will you handle ROP3 drawing? Will you implement a few codes or all of them? This is a little problem but will probably take you some time.
If your goal is to have a graphical remote access protocol, you'd be better off with VNC which is many times easier. After you've seen what it takes to implement such a protocol, you'd see what the typical pitfalls are.