Do you know of any HTTP client library in C (with SSL support) that also allows direct communication with the remote server?
I have a client-server application where the client uses HTTP to start a session in the server and then tells the server to switch the connection from HTTP to a different protocol. All communication is encapsulated in SSL. It is written in Perl and works well, but I'm looking into implementing the client in C.
I know libcurl gives you access to the underlaying socket but it's not enough because of the SSL requirement.
Notice that libcurl doesn't do the SSL part by itself, it uses OpenSSL. So, if you can get the socket handle from libcurl after the first HTTP interactions, AND the session key it uses (some spelunking required) you can go on directly with OpenSSL from that point.
I think that you must be looking for this otherwise you must have to write it yourself, like this
Sounds like you want Web Sockets. Don't know if there's a C library available though. I would assume there is, if you dig.
Related
I am trying to incorporate some SSL/TLS into some Windows Sockets. I can't find any good examples so right now I am looking into the WinHTTP API.
I am wondering if this can be used like traditional socket send() and recv() functionality? I found an example of some code from Windows here:
https://github.com/Microsoft/Windows-classic-samples/blob/master/Samples/WinhttpWebsocket/cpp/WinhttpWebsocket.cpp
I have compiled it and tested using nc and I am getting the HTTP Headers printed to the command prompt. I don't need any of those headers as I want to create my own protocol and send my own data. Is it possible to not use those headers and not use any kind of GET/POST keywords and just treat this as normal socket operations?
Or should I be looking somewhere else? I don't want to use OpenSSL or any 3rd party libraries.
WinHTTP was developed as a light-weight HTTP library to replace WinINet in service applications. It is basically WinINet without FTP/Gopher support and no user preferences.
I doubt WinHTTP allows you to perform connections that are not based on the HTTP protocol, you need to go to a lower layer like SChannel for example. SChannel supports SSL and TLS.
The Windows SDK used to have a SSPI example.
I m working with libcurl. It's very good (as client) and I used to open a socket to a server and then send my http packets.
I'm wondering if it's possible to develop http server with the libcurl. the http server will listen on a given port then when it receive a http packet then the http server return a need to a digest authentication.
I made some research in stackoverflow and in the curl website but without result.
Is it possible to do that with libcurl ? and how to do it?
To repeat what others have said: no, libcurl is not for servers. It is even said in the curl FAQ:
5.17 Can I write a server with libcurl?
No. libcurl offers no functions or building blocks to build any kind
of internet protocol server. libcurl is only a client-side library.
For server libraries, you need to continue your search elsewhere but
there exist many good open source ones out there for most protocols
you could possibly want a server for. And there are really good
stand-alone ones that have been tested and proven for many years.
There's no need for you to reinvent them!
You need some HTTP server library (since libcurl is only an HTTP client librart) I would suggest to use libonion but there are several other HTTP server frameworks (libmicrohttpd, POCO & Wt in C++, ....).
HTTP is a complex protocol, even if coding a server for a tiny subset (like plain GET requests, without all the useful features like conditional requests, encoding & compression, etc...) of it is reasonably feasible. Hence I recommend using a full-fledged HTTP server library, and that cannot be a tiny library.
I want to implement a Unix daemon (let's call it myUnixd), and want the user to be able to interact with this daemon via the command line, for example:
myUnixd --help # will display help information
myUnixd --show # will show some data (the's deamon should be doing the work)
So my question is: How can I communicate with the daemon? I was thinking about Unix domain sockets. Can someone tell me the right way to do this?
Thanks.
Use Berkeley sockets. Specifically, you can create a "UNIX domain socket" (otherwise known as a "local domain socket," which will create what looks like a text file. Write to the text file to send text to the daemon, read from it to receive text from the daemon. You can implement this with a few function calls.
If you want something more advanced, you can also use DBus, which offers a more sophisticated interface, but which is more complicated to learn.
use tcp socket if you want to use telnet to communicate with your daemon.
One could also use Remote Procedure Call (RPC) for such client-server communication. There are different types of messages (protocols) that can be used together with it, one of them is JSON.
The JSON-RPC protocol is very well accepted for such tasks. You can find different tools and libraries to embed in your software. A quick search on google gives this C library. The advantage of such libraries is that from a JSON specification file, where you define all your remote function calls, it creates client and/or server stubs that you can just use in your code out of the box.
As a listener one can use sockets, as the other responses state, or just an embedded HTTP server like microhttpd (and libcurl for the client). There are plenty of examples out there to just reuse. HTTP allows you also to run your client behind a proxy.
So, i am assuming that i will need to use sockets(i am a newbie to C).
The program will be for Windows(in pure C). And i shall be using these examples
http://cs.baylor.edu/~donahoo/practical/CSockets/winsock.html
My question is, instead of the client program connecting via TCP, i want the server to accept connections via a web browser i.e via HTTP.
So if the server program is running you type http://yourip:port/?gettemps and the server responds, but how do i do it?
As you might have guessed, this program will be for monitoring temps, remotely, via a web browser. But not for the CPU, for the GPU using AMD's ADL library(so yeah, only AMD cards).
The simplest option that is supported by most web servers is CGI - Common Gateway Interface.
Microsoft, of cource, has their own way of running web apps - ISAPI.
HTTP is quite a big standard, you might want to use some library such as libcurl to handle the details for you.
If you decide to code it yourself, HTTP is running over TCP so you first need to open a TCP socket at the standard HTTP port 80. Then simply listen on the socket and parse the incoming HTTP data - a great summary is given here: http://www.jmarshall.com/easy/http/.
Web browsers sends http get request to the server via tcp. If you are writing a web server from scratch than, you will need to parse data from web browser. http get request are string like for example GET /images/logo.png HTTP/1.1. So tokenize that string as it comes through tcp and get the command.
As you received your commands to the server call appropriate functions to handle your request.
Here is an great example of simple http server. You might want to make server multi-threaded as you may have multiple simultaneous users.
If you have already set up your web server to run the app on the appropriate port you can use getenv("QUERY_STRING") to access the web equivalent of command line parameters.
It would be better to call your program directly rather than just using the server to access a single default program as your example does, thus you could use http://yourip:port/yourprogram?cmd=gettemps. In this example getenv("QUERY_STRING") would return 'cmd=gettemps'.
I need to send an HTTP request to a server using HTTPS on Linux using plain sockets. Is there a way to do this?
Code is appreciated.
Thanks
You can encrypt the traffic with the OpenSSL library. Here is an example HTTP client: http://www.w3.org/Library/src/HTTP.c
You need an implementation of TLS (Transport Layer Security, formerly known as Secure Sockets Layer, specified in RFC 5246), whether it be OpenSSL, GnuTLS, Ajisai, yaSSL, NSS, or your own implementation (not recommended).
I think you'll need to use an SSL library, such as OpenSSL (which should be available on nearly every Linux system, or trivially available if not installed by default). AFAIK, there is no way to do SSL with only a absic Berkeley-style sockets implementation.