I'm attempting to port a Linux application to Windows. The application isn't too complex, using all fairly standard code, with few external dependencies. The main dependencies are libelf (which compiles fine under mingw), pthreads (there appears to be a win32 version available), and sockets. The main problem is with sockets...Windows provides WinSock, but this is not 100% compatible with BSD (Berkeley) sockets as used by all *nixes. What I'm wondering is, has anybody written a wrapper on windows that exposes a BSD socket API, but calls Winsock on the backend, to ease porting?
I would recommend using cygwin.dll . It's built for bringing over *nixes to windows including sockets, file IO, etc.
For the most part, you'll just have to make sure that WSAStartup() and WSACleanup() are called at start and end, otherwise, basic BSD sockets will translate pretty well. You could create some static global variable that gets checked for each call to the socket calls, and call WSAStartup() and WSACleanup() accordingly. As for poll() ... well, it translates quite easily to select().
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I am trying to understand how code, regardless of the language, works. Specifically thinking about software that runs on Windows.
Is my understanding correct that every built in function of a particular language maps to an exposed function in the Windows API when writing software for the Windows platform?
I guess my question can be even more generally, can a language do anything outside of what the OS provides? If so, how? What is an example of this?
There is a theoretical and a practical answer to this.
Practical: yes.
The WinAPI is the API everything uses to do things on Windows. It’s stable and compatible between versions so you can write whatever you want with it and it will work on practically any version of Windows given you don’t use any APIs that aren’t present in an old version. There isn’t any other interface to talk to the operating system properly.
Any language or platform that wants to work on top of this will call WinAPI. C libraries, Python, etc all are written so that they work on top of it (often other languages use C or C++ libraries which use WinAPI).
Theoretical: no.
Windows itself includes a Native API which is the actual OS interface and WinAPI is built on top of this. It is not really used if it’s not necessary since it’s not really documented. It’s used in a couple of Windows components that need to run before the other parts of the system are running and you can build applications linking to this API. But since it’s undocumented it’s not really reasonable and may change whenever.
There is also the syscall level. Several Windows components provide the lower level services for operations done on the WinAPI level. You can write, for example, an assembly program and use the syscalls directly if you want to. Mostly you don’t want to so this is more of a theoretical rather than practical answer to different platforms communicating with the OS. These also may change based on the OS.
WinAPI is basically only one subsystem that runs on the NT kernel. For example, Windows Subsystem for Linux is another one which implements its own syscalls which are then translated to Windows ones. There has also been a POSIX subsystem previously.
So all in all it depends on which level you look at it, but the practical answer is yes. Everything practically runs on WinAPI.
Yes. Even if an application exits immediately, it uses a windows call.
So it is not only theoretical. In theory, as in practice, every Windows application uses the API, because there is nothing else to use.
Even if you try to rewrite each functionality you are about to use, you would eventually have to install a driver, and this also mean you would use the API.
I am trying to port code using boost.asio onto the esp32 (esp-idf) which in turn uses lwip, mbedtls and FreeRTOS using preemptive multitasking.
The esp-idf exposes a Linux/Posix-like interface and most stuff compiles out of the box. Lwip exposes a standard BSD socket interface including select() and blocking and non-blocking sockets etc, but it does not have poll().
So in principle I would think that everything should be there to make boost.asio happy. What I find is that boost.asio (e.g. socket_ops.ipp) contains code variants for many OSes, and it is clear to me that esp32 is not a supported platform.
My question is: What is currently the best alignment of the BOOST_ASIO_* #defines when targeting the esp32?
(I am currently drilling into this and I am modifying both boost.asio and the esp-idf to fit together, but I already made unnecessary changes, thus asking this question.)
There are a few programs like Proxifier that can force an exe to use a proxy. There are a few others, too. But the sites all look a bit shady. I don't even trust Proxifier tbh... So I'd like to know how these programs work. How do they do it? Is there a WinAPI function that can be used to do that? Or do you have to actually inject code into the processes?
I was only able to find functions to change the global proxy of windows. But some programs don't care what the global proxy says, they always try to connect directly, even if it's not possible...
Proxifier is based on LSP (layered service provider), but personally I never liked this technology because of often stability issues. However, besides LSP there are other possible approaches suitable to achieve the same functionality, you can find a short coverage of network filtering methods (including LSP) here: https://www.ntkernel.com/ndis-hooking-drivers-and-legacy-windows-systems/, however the document is a little bit out-of-date, I have written it in times of early Windows XP dawn and it does not cover WFP (Windows Filtering Platform), which replaced TDI, and NDIS Lightweight Filter, which replaced NDIS Intermediate and NDIS-hooking drivers. Both technologies were introduced by Windows Vista along with NDIS 6.0.
I think Wininet.dll is the canonical method for accessing HTTP from user mode programs on Windows. (The documentation for Windows Networking and Internet support is here. I didn't want to go through all of the doc, but I'm pretty sure Wininet.dll is the right one)
One method for doing a per process proxy, is to write a DLL that acts like Wininet.dll (and sits on top of the Windows' Wininet.dll). Your Wininet would have some sort of mechanism (registry, config file, etc.) to determine whether a particular process is to be proxied or not. If process isn't proxied then all calls go through to original Wininet, but if process is proxied then your Wininet does the redirection.
Another, somewhat similar, injection point is at the winsock layer (ws2_32.dll). (Back in the Windows 3.1, Win95 era, it was fairly common to replace winsock.dll (ws2_32 predecessor) by vendors of TCP/IP stacks.) Here's a case where the same concept is used to capture traffic at winsock layer. The article at the link has a nice diagram that illustrates the concept as well as implementation details of replacing ws2_32.dll.
The modern way to do this is to use Windows Filtering Platform.
https://en.wikipedia.org/wiki/Windows_Filtering_Platform
https://learn.microsoft.com/en-us/windows/win32/fwp/windows-filtering-platform-start-page
Windows Filtering Platform (WFP) is a set of API and system services
that provide a platform for creating network filtering applications.
The WFP API allows developers to write code that interacts with the
packet processing that takes place at several layers in the networking
stack of the operating system. Network data can be filtered and also
modified before it reaches its destination.
I want to use parallel port (LPT) to receive and send data, i have done that before in various language in different OS, like VB in windows, C in linux.
But now, i want to use a language (and a library for LPT access i guess) which is cross platform. So that i can write code in linux and can compile that on my father's windows without changing the code.
The java comm api would be a great choice but official api doesn't support windows and rxtx is 2 years old.
So which language and library will be easier and efficient, i mean, easy to bundle, easy to install etc... and i need linux and windows compatibly.
Parallel port i/o has no standard portable interface. On MSDOS, Windows, and Linux, significantly different paradigms and APIs are used.
The best you can do is write an application which uses an abstract API and then provide that API on each of the target platforms. There are probably already libraries available which does the lower part, but I don't know of any offhand.
on windows, is there any other option when programming network communication then using Winsock? There are many socket libraries for c++, are they all just winsock based?
You can consider using boost::asio. Boost is really great and well designed. Many parts of it have come already into C++0x. You will need to statically link to a lib or dll (it is not a header only template library)
Winsock are the sockets for Windows taken over from BSD (with actually exactly the same API excepting for closesocket vs close and the initialization/termination of the subsystem). Not the Win API itself has a more modern API the WSAxxx functions. C++ is socket unaware until now that means in order to do networking you MUST use the OS API, thus Winsock. There is no other low level API.
If you are trying to monitor traffic why don't you use WinPCAP?
There are other ways to program network communication, which don't use Winsock: for example, using the network file system (shared files), or using named pipes.
Software can also bypass Winsock (which is a Windows user-mode DLL) even for TCP/IP traffic, and instead interface directly with the kernel-mode drivers.