I'm implementing a RESTful web API in an embedded stack which provides a webserver without the REST feature. To be precise, the embedded stack is RTCS which runs on top of the MQX RT operating system, the microcontroller is a Kinetis K60 from Freescale. I'm able to distinguish GET/POST/DELETE/PUT requests and to get the url with the parameters (let's say /this/firstValue/that/secondValue/...).
I use strtok to separate the different elements of the url and take decisions. But my code is just ugly because it's full of strcmp functions and if statements. I also need to check bounds for firstValue and secondValue (which I could do in set/get functions, but 2 functions for each parameter will be repetitve). Moreover I'd like to be able to add parameters without messing around with the decision tree.
I have two questions:
How would you make the code nice and dry?
Do you think a REST webservice is appropriate to control my microcontroller over the network? Do you have examples of such things? I'm using a REST webservice because it provides authentication (no secrecy however because I can't setup SSL sockets yet) and I think it's an elegant solution.
I evaluated some other solutions:
SNMP (snmpset/snmpget): it worked but setting up the MIBs was a real pain, and since it's SNMPv2 there is still no secrecy.
telnet server (I have no SSH solution yet): I don't see any advantage/drawback aside that REST will probably be easier to control from the outside, I'm testing it with curl :)
SOAP Remote Procedure Call (I just don't like it)
Any other idea ? I need something simple and scalable since there could be multiple targets to control. I have limited resources :s. I would need secrecy at some point, and I expect to have it when CyaSSL (an embedded ssl implemetation) is ported to MQX. They said it's happening next month so secrecy won't be an issue anymore but if you have other ideas...
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Emilien
REST is an architectual pattern, So i guess you mean your server provides HTTP.
A resource is 'any data that can be named'. e.g. an LED on your embedded device could be a URI of '/leds/led3' You could change the data it holds (its state, rgb led? etc) with the standard PUT request, and GET should return its current state.
As for coding it, a generic tree structure maybe wise if memory permits to make path finding as simple as possible. With the data and function pointers (emulating objects) at the leafs
Related
I am writing a game hack and want to run cheat engine while the game is running, the anti hack currently detects both the user mode and kernel mode components and terminates the game. I wrote a device driver to hook ZwQuerySystemInformation to hide the process. I would also like to hide the device driver since it is currently still detected.i know i could do this with DKOM but id prefer to use a SSDT hook, does anyone know what api i should hook to filter the list of services/drivers?
You can follow this article from the beginning to the start and use its supplied code and customize it to fit your own needs: http://www.codeproject.com/Articles/46670/Service-Hiding
Word of advice, if you don't know what you are doing, its best to not play with such stuff.
On a side note, they tend to over complicate their architecture and compilation process so expect some hiccups as its not going to be straightforward solution. But, this should address and solves your question and needs.
EDIT:
You would need to hook the services API that is responsible for showing you what services are running currently on your computer. An example for this is "services.exe" this is where all the data structure(s) you would need to modifiy/alter to properly hide your driver. In specific the SERVICE_RECORD structure and the following members needs to be modified as well: Prev, Next and ServiceName. Once you have found such structure inside services.exe its back to basic algorithm 101. Which is to drop the required driver that you want to hide from those doubly-linked list. The following image is courtesy of the article mentioned before.
This is the basic or general rule behind hiding the service.
I'm looking for the simplest possible (cross-platform, but not necessarily cross-browser) code to send data from a local web page to a C (not C++) application running locally. Basically, I have an HTML page with a form and I want to send the data from that form to another process in the simplest way possible. (I know that I can read local data from a webpage relatively easily, especially now with HTML5, but writing outside of the javascript sandbox is a mystery.)
I know that browsers make this very hard to do for security concerns, and I don't want to open up my machine to attacks, but maybe I can run a very simple server inside the C application to receive the submitted data... Either way, I cannot run any standard webserver, so I need to have a C library/app that does it for me.
I've looked into .hta files (seem to only work for Windows) and some C web servers (all I've found are *nix specific). A similar question is how to transfer of data from webpage to a server c program , except that user allows the use of Java and other webserver platforms (I must use C).
UPDATE: Promising libraries: https://stackoverflow.com/questions/175507/c-c-web-server-library
Have you considered FastCGI? I have a fast CGI library written in C that might be helpful. It still needs a lot of work and I'm not sure if I would want to use in a production environment.
If you find any bugs or make any enhancements, please share them so that it can help others.
https://github.com/manvscode/shrewd-cgi
You could write a very simple web server in C, serve the page from it (avoids security issues), and post the form to it.
If you're bound to c, you'll have to go low-level and deal with all the nifty details around the sockets library. (There's a reason why people abstract that in high-level languages). Check out some example code for RPC in C with server and client here. If you can afford to bind to C, e.g. using Tcl, i would implement the server in a tcl script and bind your C functions as a Tcl command. That way you pass the content directly to your c method while avoiding to write all the sockets code low-level.
Send the desired data from web to specific port of your system (for example port X). Then run your application (e.g. APP) in background using following command:
nc -l X | ./APP
And of course you need nc package.
We have an existing C library (DLL / .so) that processes some data. There's a call to initialise it, then a call to give it the parameters it needs to process, and then a few calls to retrieve the different output parameters you are interested in. The initialise is then called to reset the library for the next session. We have an app built around this to easily input the data and view the results.
Now we want to take this library and make it available as a web service. We are looking for the simplest (read quickest) way to do this. As I see it, we need:
A web services framework (Apache Axis2/C looks good for existing C code)
Some way to start a process for each incoming query (not sure if Axis2 can do something like this).
So my question is : Is Axis2/C the simplest way, or is there another simple solution?
If you have an external executable you can call, how about using something like Apache with FastCGI?
I want to create an application in C that allows two users to share a file. I'll call the person sending the file the server and the receiver the client. There are a few requirements:
The users need no identification, no "login". You could say they are unknown for my application.
The server selects a file for transfer and gets returned a simple ~10 character ID string/hash that the client can use to retrieve the file.
The same application is used for both serving and receiving.
My application must not need dedicated software running on a remote server, unless it's freely available (e.g. bittorrent trackers).
Now this sounds a lot like bittorrent and I am seriously thinking of doing this through bittorrent. I'm not sure how I would do this. Are there any good libraries for torrent creation / seeding / downloading?
Please answer this question by either:
Posing a viable alternative for bittorrent / other ideas.
Posting good libraries / snippets / implementations of the bittorrent protocol in C.
This does indeed sound like something best done with BitTorrent. Have you had a look at libbt? It's not very well documented but does include a sample client, which is btget.c in /src/.
I have now found this library: rasterbar libtorrent. It's in C++ but I don't mind (I don't know either that well anyway).
Sharing here for future reference if other people are looking for the same thing as me.
And an other solution, send the file through an IRC server (like Freenode). I came up with this solution after I had trouble with opening ports with bittorrent.
I am afraid that several terminologies in my question are wrong. Please bear with me and correct me wherever I am wrong.
I have to write a library/program that will provide set of function to operate a card reader attached at Serial Port. Like to eject card that was inserted in it, user will simply have to call in his code, for example,
cardEject(); // or
track2Data( response); // to read data of track 2 of magnetic stripe.
cardEject() and other functions will themselves take care of opening serial port, writing data to it, checking the acknowledgement, checking error code, resending command in case of failure, etc. I am pretty clear about communicating with devices on serial port.
My question is, after writing all these functions and testing them, how should I provide them to the user.
Should I give him a header file (.h) and an object file (.o)? So that he can link to the object while compiling his actual program.
Should I provide a static library (.a)?
Which one is a better idea?
Is it a good idea that each function open serial port and then close it? Or a initCardReader() opens it, sets its properties and closeCardReader() should close it? All other functions can only be called after initCardReader()?
Now a silly but real question :-) what is the terminology used for such programs? Is it a driver or library or device interface? What is the correct label for such projects?
Thanks for your time.
Edit
Thanks to all of you for guiding me. Really appreciated.
This API has to become part of a larger project. In fact, I will be working on that project too. But there is a strong possibility that this API will be used in other projects with or without me. I think, considering the possible use in other projects, library makes more sense. Kindly correct me if I am wrong.
I'll go with the answer from Anders K. you are writing a API for your card reader.
My two cents about the more general questions:
Your question about open/close connection, there are two aspects that you have to keep in mind. Lets assume you proceed the way in which you leave it up to the user to open and close the connection. What if he forgets to close it after he finished, what when multiple processes access the card-reader? In those scenarios you may want to free the port to the other processes after each write/read. In the end it depends on the operations that will be done, the process using your API will usually always call your read method multiple times you might want to leave it open or you could implement a read multiple records in your API again avoiding the possibility that a connection gets left open.
I would make a library if it is mainly used in other projects. It also puts you into the position of changing the lib at one place for everyone to implement. Again depending on where you will implement it, there are numerous scenarios when adding your code is the better option.
I think you should do it as simple as possible, a static library and a header file should be a good start.
One way is to treat the card reader in the same way any other resource like a file, meaning you open/init the card reader and return some handle that identifies the card reader. Then subsequently use that in all functions when accessing the card reader.
My two cents:
I think how you provide the output depends on the user. Is this person working closely with you in the same company / project, or is this going to an external source?
If its going external definitely make it a library...it may be easier to create a library in the other case as well, since it would mean less things for this other user to worry about.
Is your code going to be integrated into a larger project? If so, you should just build your code into a subfolder in this project and provide him with the required functions that are needed. I think this portion is more subjective than anything.
Regarding opening/closing the ports, again it depends how it will work. If you are simply providing the API for other programmers to use (and don't know how it will work), I would say abstract it into an initCardReader/closeCardReader function call. That way, if the user wants to do multiple transactions he doesn't need to worry about wasting processing time with each call he makes...he can simply open/close at his discretion.
And it sounds to me like you are writing API calls for a card-reader device driver ;)
You can put this set of functions in the shared lib (like: libCardReader.so) and give away with the Header file to the programmer to reference and use it in his/her code. The following link provide very good intro about building the SO file (http://www.network-theory.co.uk/docs/gccintro/)