I have a Linux C++ application which run as a daemon. When user executes this application, it will be running in the background, listening on a port, and waiting for connection from the clients.
Is it possible to port this kind of application to Windows platform using Cygwin or MinGW?
Thanks.
Cygwin aims at POSIX/Linux source level compatibility, so your application is supposed to build and work there with no or only minor modifications.
MinGW does not try to provide such a compatibility layer. It's just the GNU toolchain for Windows, so you would need to replace any uses of POSIX/Linux-specific APIs with Windows equivalents.
It is possible to port almost anything (unless it makes sense only to one OS). The question is, "how hard is it to port application X"? And to help answer that question, we need to see source code.
General purpose tips
It basically boils down to how much compiler/system-dependent code you've spread out over your code base. I see you're using at least two things that are sensitive: daemons and sockets.
Daemons are tricky to port as the equivalent on Windows (a windows service) requires different platform-specific code. This is fixed cost (e.g. does not vary on the size of the rest of the application).
Sockets are more or less tricky to port depending on whether you're using advanced networking features (asynchronous I/O, etc.), which tend to vary more from system to system. It also depends on whether you abstracted socket manipulation code into some re-usable component. Windows supports a very similar sockets interface (the classic BSD socket interface with minor modifications to random parts of the API). Changing one Socket class is easier than changing your code if you didn't write a wrapper class.
Related
I'm currently getting familiar with PLC's, the WAGO 750-8206 PLC in particular. It offers a linux OS and can run CoDeSys programs. There are some I/O modules attached to the controller: 750-530, 750-430 and 750-600. What I would like to know is this:
Is it possible to write a C++ linux application that runs on the PLC and gets/sets the digital inputs and outputs?
Even better: can I write a CoDeSys program that "talks to the I/O's" and handles all the logic and at the same time can be accessed by a C++ linux program? THe idea is this: I would like the CoDeSys program to check for let's say two digital inputs. If both are high, a variable should be set to a defined value. The linux application should be able to read that variable and conduct further processing (such as sending JSon data to a server or similar).
Also, I would need to be able to send commands from the linux application to the CoDeSys program in order to switch digital outputs (or set values on analog outputs etc) when the linux application receives a message that triggers the command.
Any thoughts and comments on this topic are greatly appreciated as I am completely new to this topic. Thanks in advance!
The answer you might want
The actual situation has changed into the opposite of the previous answer.
WAGO's recent Board Support Packages and Documentation actively support you in making changes and extensions to the PLC200 line. Specifically the WAGO 750-8206 and 17 (as of March 2016) other PLCs :
wago.us -> Products -> Components for Automation -> Modular WAGO-I/O-SYSTEM, IP 20 (750/753 Series)
What you have to do is get in touch with them and ask for their latest Board Support Package (BSP) for the PLC200 line.
I quote from the previous answer and mark the changes, my additions are in bold.
Synopsis
Could you hack a PFC200 and get custom binaries executed? Probably Absolutely yes. As long as the program is content to run on the Linux-3.6.11 kernel and glibc-2.16 and is compiled for the "armhf" API, any existing ARM application, provided you also copy the libraries it uses as well, will just run without even compiling it specifically for the PFC200.
Would it be easy or quick? No. Yes, if you have no fear of the Linux Command line. It is as easy as using the Cross Compiler provided by the Board Support Package (BSP) with the provided C-libraries and then run this to transfer your program to the PFC's flash and run it: scp your-program root#PFC200:/usr/bin
ssh root#FC200 /usr/bin/your-programOf course, you can use Eclipse CDT with the Cross Toolchain for the PFC200 and configure Eclipse to do do remote run and debug.
Will this change in the future? Maybe. Remember that PFC200 is fairly new in North America.It has, PFC200 has appeared in September 2014
The public HOWTO Building FORTE for Wago describes how to use the initial BSP to run FORTE, which is the IEC 61499 run-time environment of 4DIAC (link: sf.net/projects/fordiac ), an open source PLC environment allowing to implement industrial control solutions in a vendor neutral way. 4DIAC implements IEC 61499 extending IEC 61131-3 with better support for controller to controller communication and dynamic reconfiguration.
In case you want to access the KBUS (which talks to the I/Os) directly, you have to know that currently only one application can be in charge of KBUS.
So either CODESYS, or FORTE, or your own KBUS application can be in charge of the KBUS.
The BSP from 2015 has many examples and demos how to use all the I/O of the PLC200 (KBUS, CAN, MODBUS, PROFIBUS as well as the Switches and LEDs on the PFC200 directly). Sources for the kernel and with all kernel drivers and the other Open Source components is provided and compiled in the Board Support Package (BSP).
But, the sources for the libraries and tools developed from scratch by WAGO and are not based on GPL/Open Source code are not provided: These include the Application Device Interface(ADI)/Device Abstraction Layer(DAL) libraries which do CANopen, PROFIBUS-Slave and KBus (which is used all PLC I/O modules connected to the main PLC unit)
While CANopen is using the standard Linux Socketcan API to talk to the kernel and you could just write a normal socketcan program using the provided libsocketcan, the KBus API is an WAGO-specific invention and there, you'd have to do some reverse-engineering if you'd not want to use WAGO's DAL for accessing all the electrical I/O of the PLC, but the DAL is documented and examples how to use it are provided in the BSP.
If you use CODESYS however, there is an "codesys_lib_demo-0.1" example library which shows how to provide a library for CODESYS to use.
Outdated Answer
This answer was very specific to circumstances in 2014 and 2015. As of 2016, it contains incorrect information. Still going to leave as-is for now to provide background.
The quick answer you probably don't want
You could very reasonably write code using Codesys that put together a JSON packet and sent it off to a server elsewhere. JSON is just text, and Codesys can manipulate text in a fashion very similar to C. And there are many ethernet protocols available from within Codesys using addon libraries provided by Wago.
Now the long Answers
First some background
Since you seem to be new to Wago and the philosophy of Codesys in general... a short history.
Codesys is used to build and deploy Hard Realtime execution environments, and it is important to understand that utilizing libraries without fully understanding the consequences can destabilize performance of the entire system (bringing Codesys to its knees and throwing watchdog errors in the program). Remember, many PLC's are controlling equipment that could kill someone if it ever crashed.
Wago is fond of using Linux to provide the preemptive RT kernel for the low level task scheduling and then configuring Codesys to utilize much of the standard C-libraries that often accompany linux. Wago has been doing this for quite some time, but they would never allow you to peel back the covers without going through Codesys (which means using IEC 61131 languages, of which C++ is not included), and this was for your own safety (and their product image). If you wanted the power of linux on a Wago, you had to get a special PLC with a completely naked OS, practically no manual or support, and forfeit the entire Codesys runtime.
The new PFC200's have much more RAM and memory available than recent models, allowing for more of the standard linux userland stack (ssh, ftp, http,...) to be included without compromising the Codesys runtime, and they advertise this. BUT... they are still keeping a lid on compilation tools and required header files needed to compile and link to Codesys libraries or access specialized hardware (the Wago KBUS, which interfaces your I/O modules).
The Synapsis
Could you hack a PFC200 and get custom binaries executed? Probably yes.
Would it be easy or quick? No.
Will this change in the future? Maybe. Remember that PFC200 is fairly new in North America.
Things you may not know
Codesys does not necessarily know or care about Wago. You can get Target Platforms for Codesys that do target Intel processors running a linux os. Codesys DOES SUPPORT accessing external libraries (communication in the reverse direction is dangerous), but they often expect a C style interface, and you can only access those libraries by defining C-headers that Codesys will analyze, so you may need to do some magic to get C++ working seemlessly. What you can do is create a segment of shared memory that both C++ and Codesys access, and that is how they pass information (synchronization is another problem).
You can get an Open Wago PLC, running Codesys on Linux. Wago's IPC are made specifically for this purpose. They have more power, memory, and communication capabilities in general; but they do cost more than double your typical Wago PLC.
If you feel like toying with the idea of hacking a Wago, you will need to tear apart the manuals for Codesys (it has its own), the manuals for the Wago IPC's, and already be familiar with linux style inter-process-communication and/or dynamic libraries.
Also, there is an older Wago PLC that had the naked Linux on it 750-8??. It also has a very good manual on how to access the Wago hardware using supplied headers.
You must first understand how Codesys expects to talk to its target operating system. Then you work backwards to make it talk to Wago specific libraries living on that operating system. You must be careful not to hijack Codesys.
Your extra C++ libs should assist Codesys, not take it over. For instance, host a sqlite database on the same device, and use C++ to manage the database and provide a very simple interface that Codesys can utilize. All Codesys would do is call a function and pass some values, but your C++ would actually build an SQL query and issue it to the database (Codesys doesn't need to know why or how this is happening).
I hope at least one paragraph is helpful in some way.
I just have a simple question. I am a student and I am learning. I am not very proficient at C++, but I finally set up a working http reqest app in c++ using winsock and I just wanted to know that after compiling will the http request still be sent from other OSes that don't have WinSock?
WinSock, or at least the parts you probably will have been using for introductory networking stuff, is based off of, and largely compatible with, the BSD socket API, which is available on all current operating systems. If you don't have experience with cross-platform development it's unlikely that your code would compile the first time through on a Linux system, but the underlying techniques would be the same.
For cross-platform networking, you might want to consider something like Qt, which provides an API which will work mostly the same on all OSes without much per-platform stuff. Its networking API is also based off Berkeley sockets.
In general, though, there's just no way of checking that your code works cross-platform without testing it cross-platform. Grab a Linux distribution and try it out; note that some are specifically intended to work from your Windows disk without the need to repartition.
If you use standardized BSD-based socket functions, then your code will typically work on multiple platforms socket(), bind(), connect(), send(), recv(), etc. Caveats include:
error codes. When a WinSock/BSD function fails on Windows, the error code is retreived using WSAGetLastError(), whereas other platforms use errno instead. So you will have to wrap that portion if you are trying to write cross-platform code.
get/setsockopt() may implement different options on different platforms, not all options are standardized across all platforms.
If you use WinSock-specific functions, then your code will only work on Windows. WSASocket(), WSAConnect/Ex(), WSASend/Ex(), WSARecv/Ex(), etc.
All versions of Windows have WinSock. Most platforms, including Windows, support a BSD-based socket API.
After you compile your code, it will only run on the specific platform it was compiled for. You would have to compile the code separately for each platform you want to support.
I'm designing a training program in C++ that will be distributed to a large number of facilities, most of which won't have much in the way of an IT staff. The program connects via a TCP connection to a central database which stores various pieces of data for research and evaluation purposes.
The problem I have is that I would like to make the transmission secure, and the most commonly recommended way to do that seems to be OpenSSL - which seems all well and good, but I've got a problem. As I understand it, OpenSSL must be installed specifically on each of the systems. The facilities won't have the expertise required to compile and install the source on their systems, the computers will be sufficiently varied (all Windows boxes, but of varying make and quality) to rule out distributing a specifically-compiled binary, and continent-wide distribution makes it impossible for my team to personally set it up.
Does anyone have a recommendation for how to solve this problem? Am I simply incorrect in my assumptions, and one can distribute it without installation? If not, is there a more practical alternative?
As long as all your machines are XP+, with two versions of OpenSSL you should be ready, one for 32bits and one for 64bits. Just provide two separate installers and that should be it. There's no need to compile for each machine.
Just remember to include the Visual C++ redistributable package in your installer as well.
If you have to support ancient Windows versions, it gets a bit more complex but not that much.
Actually, OpenSSL seems like a good option based on what you described.
From what I understand of OpenSSL, it is a library written in C (with wrappers around it for other languages), meaning that you can include it in the code base of whatever it is you are writing.
I'm pretty sure that it is not a program that has to be installed, so I think that you shouldn't have to worry about that.
You might also like to experiment with IPSEC- if you are concerned with distribution of binaries etc to client machines, IPSEC could be interesting solution. Since virtually all Windows boxes support it, all you have to do is to configure IPSEC policy on DB server - by making it as "required" this way, all the data between client machines and DB server will be encrypted.
I need to make a connection through wireless or LAN. I have done this on Windows (VS2008 C#, Sockets), but not on Linux (Ubuntu 10.04). I have installed mono, and I can handle many things there, but it's speed is unacceptable for my 600MHz processor, so I decided to move on C++, but I'm new to C++ and I'm not familiar to many of it's headers. Is there any header or library which can do that for me?
How the actual connection is done (if wireless or cable) should be up to the system; if you want to use sockets, I suggest reading of beej guide to network programming , it contains everything (or so) you need to know. It's C mainly, but reusing it for C++ needs no effort.
Did you think about using boost::asio, this way you can share at least the code between linux & windows. The overhead is not that big compared to naked sockets and you have the benefit of better semantics. Many parts of code from boost have flown into standard C++ so the code is of rather high quality.
I wonder what library would ease the development of a cross-platform service/daemon ? (C/C++)
I'm targeting: Windows, Linux and OS X.
Requirements: network operations and serial port communication.
Also it would be nice to have a basic sample service application.
When it comes to Qt you might try qt-service.
A daemon in Linux is really just a process that runs disconnected from a terminal. In Windows, a service is something that can be controlled using the service management API, but once again is basically just a disconnected process. The disconnection aside, daemons & servers don't have much in common, from task to task. There is no requirement, for example, that they be multi-threaded, be asynchronous or perform network I/O. Given that, it's kind of hard to see what a cross-platform library would do.
You should take a look POCO. Depending on what you are doing it could have facilities to do a large amount of the work for you with a lot less work than Boost.
An obligatory mention for ACE though I don't personally care for it much.
Boost probably has most of what you need in terms of threading and networking I/O.
You may also find Qt a good alternative. It also has threading and networking libraries and has a much easier to use & understand event-driven programming model using a run loop. Qt's signal/slot system is very easy to use and ideal for a network daemon/service (Boost also includes a signal/slot system but it is harder to use and does not include an event loop; you have to roll your own using some event library). As a cross-platform library, Qt can handle many of the issues in bridging the Unix (OS X and Linux) vs. Windows mental model for processes, filesystems, etc.
For unit testing, I've been very happy with Google's C++ unit testing library called googletest (though both Boost and Qt also have built-in unit testing systems). It runs on all the platforms you specify. I've done a lot of work with googletest on cross-platform Qt projects and found it quite satisfactory.
I've found a big library in the non-boost version of ASIO. You don't need all boost library but only this little headers-only and very well documented library http://think-async.com/
As examples, a daytime server-client system is implemented in very few lines of code.
Take a look at it.
(remember to look at the non boost-ized version)