Enabling JSON communication with HTML GUI

[Cyril Albrecht]

Hello there,

For my Bachelor thesis I need to enable communication (JSON) between a GUI coded in HTML/JS and a program in C++. For this I tried to use civetweb to create a server and send some dummy data from C++ to the GUI. The idea is that the user sets some parameters on the GUI, and then the C++ part computes everything and sends back the result. As I don't know so much about internet connection, I have trouble connecting both ends of my project.

On the C++ part, I could create a server which shows the correct webpage. I just don't know how exactly to connect it afterwards. I guess I would need one of the handle to send data (post or put) and another one to receive data (get), but not sure how to use those.

Here is what I got for now:

        std::vector<std::string> options = {

        "listening_ports", "8080",

        "document_root", "..\\res\\html",

        "enable_directory_listing", "yes",

        "static_file_max_age", "0"

    };

    CivetServer *server = new CivetServer(options);

    CivetHandler *handler = new CivetHandler();

    server->addHandler("/json", handler);

    ShellExecuteA(NULL, NULL, "http://localhost:8080/index.html", NULL, NULL, SW_SHOW); // open browser

    std::stringstream  responseStream;
    responseStream << "Content-Type: application/json\r\n"
                   << "{"
                   << "\"result\": "
                   << "\"dummy\""
                   << "}";


    char buffer[1000] = "";
    mg_connection *conn;
    conn = mg_connect_client("localhost", 8080, 0, buffer, 1000);
    handler->handlePost(server, conn);
    
    std::stringstream str;
    str << "HTTP/1.0 200 OK\r\n"
        << responseStream.str()
        << "\r\n";
    mg_printf(conn, "%s", str.str().c_str());

mg_printf gives back some positive value the first seconds, then switches to -2. Is this the timeout of the server ?

And on the GUI side I got:
  var task = window.setInterval("update()", 250);
  function update() {
    $.getJSON('/json', function(data) {
      refresh(data);
    });
  }

But for some reason, I cannot access to 'http://localhost:8080/index.html/json', where I should be able to see the dummy JSON output.

Could any of you help me with this project, or show a good working example for something similar ?

[bel]

Did you already have a look at this example:

https://github.com/civetweb/civetweb/tree/master/examples/rest

It's not yet complete ... I have to clean the html/js demo script before I add it to the repository.

Bbut the server side will already send you a JSON response.

--
Sourceforge
https://sourceforge.net/projects/civetweb/
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[Cyril Albrecht]

Hi bel, thanks for the quick anser.

After discussion with my professor I got a working implementation for Linux. After removing some parts which were not compatible with Windows, I could make it work properly on my computer.