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?
Related
My question should be very simple to answer for anyone not being a self-taught newbie like me...
On this page is a cheatsheet concerning a function to be used in GIS/DB environnement : http://www.bostongis.com/pgsql2shp_shp2pgsql_quickguide.bqg
I would like to create a script allowing users to just have to click on it to launch the process, given the proper datas. But I don't understand how to use this. It obviously doesn't work in a Python console, nor directly in the windows console. How is it supposed to work ? What language is this ?
Thanks
shp2pgsql is indeed a command line tool. It comes with your PostgreSQL/PostGIS installation (usually) and, if not accessible via PATH-variable, can (usually) be run from within the /bin-folder in your PostgreSQL-Installation. You can also always 'make' the programm from source in any location yourself, if needed.
EDIT:
One way to set up a script (independent of whether you use it within qgis own python environment or not) would be to use Pythons subprocess (or os.system) module (check related question here) to write to shell and execute shp2pgsql.
A slightly more sophisitcated solution to (batch) insert (multiple) shapefiles via script could be to implement ogr2ogr via gdal/ogr module within python (check this blog). That, however, would require a working installation of the gdal core library, and the respective Python bindings (at least to use outside of QGIS Python environment, where it is pre-installed AFAIK), which can be tiresome at times. Once installed correctly, it offers a powerful (I dare say almighty) toolset for geodata management and manipulation via Python, though.
Apart from that, the blog link I provided also states the implementation of a batch insert script/tool (which operates ogr2ogr) in qgis 2.8 toolbox...maybe that can help you, either with your work directly or (via sourcecode) to point you in the direction of creating your own tool.
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...
--
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
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.
Would like to ask for advice.
there is a need for binary to have a mechanism for self update. Lets imagine binary rolls on host A and updates-server is server B.
Lobster method is to fork bash script with wget/ftp/ncftp/etc getter wich will download and replace. But ehm...there is no such tools on A and they will not be installed.
In short I can't use any external software tools(external to running binary).I can just hardcode mechanism in running binary.
As binary image runs it can load binary(and md5 file) simply via tcp sockets in tmp file,then do md5 compare and if everything ok then replace binary and restart itself. Its easy to do, but I have some strange feeling...dunno.
Mb someone can share and advice?:)Thank you in advance.
Conditions: binary is written in pure c. freebsd is binary rolling side and update-serve is centos. So java/python/c++/any is available at server side but not on free. Y, tobe honest its is possbile install some tools on client side and openfirewall for ftp, but want to avoid and hardcode :)
ADDED: must be noted that the enviroment between A and B is secured..eghm...as we think, in any way security and access problem and spoofing/sniffing out of our world there :) its just local update implementation mechanism for some binary which nowdays we update from center within expect scripts via ssh.
You will have to reimplement a whole host of functionality if you want to do so. My easiest suggestion would be to link to libcurl, hardcode the download path into your executable and write the image of your executable back to $ARGV[0]. However, you should definitely rethink your distribution concept, most distributions do some form of package management, and using it is the easiest alternative for all parties involved.
First of all check if you can modify a binary when a process is executing it, some system does not allow it.
You say you can not use external tool so probbly you can not create another "updater program" which will do the chenge instead of your binary.
Probalby you can download such program (from where you want to downlaod your update), execute it (exec, replaces current process with the new one)
that executed process will download and upded your main one, and then exec to it.
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.