add very simple Webclient class. needed for LAS-22, LAS-23, JSON-54 etc.

webclient.cc

@@ -0,0 +1,73 @@
+#include "webclient.hh"
+
+#include <string>
+#include <stdexcept>
+#include <boost/beast/core.hpp>
+#include <boost/beast/http.hpp>
+#include <boost/beast/version.hpp>
+#include <boost/asio/connect.hpp>
+#include <boost/asio/ip/tcp.hpp>
+
+namespace pEp
+{
+
+namespace beast = boost::beast;     // from <boost/beast.hpp>
+namespace http = beast::http;       // from <boost/beast/http.hpp>
+namespace net = boost::asio;        // from <boost/asio.hpp>
+using tcp = net::ip::tcp;           // from <boost/asio/ip/tcp.hpp>
+
+
+HttpError::HttpError(unsigned error_code, const std::string& error_message)
+: runtime_error("HTTP Error: " + std::to_string(error_code) + " " + error_message)
+{}
+
+
+// based on https://www.boost.org/doc/libs/1_75_0/libs/beast/doc/html/beast/quick_start/http_client.html
+std::string Webclient::get(const std::string& url)
+{
+    // The io_context is required for all I/O
+    net::io_context ioc;
+    
+    // These objects perform our I/O
+    tcp::resolver resolver(ioc);
+    beast::tcp_stream stream(ioc);
+    
+    // Look up the domain name
+    auto const results = resolver.resolve(m_server_name, std::to_string(m_port));
+    
+    // Make the connection on the IP address we get from a lookup
+    stream.connect(results);
+    
+    // Set up an HTTP GET request message
+    http::request<http::string_body> req{http::verb::get, url, 11};
+    req.set(http::field::host, m_server_name);
+    req.set(http::field::user_agent, "pEp::Webclient 0.1");
+    
+    // Send the HTTP request to the remote host
+    http::write(stream, req);
+    
+    // This buffer is used for reading and must be persisted
+    beast::flat_buffer buffer;
+    
+    // Declare a container to hold the response
+    http::response<http::dynamic_body> res;
+    
+    // Receive the HTTP response
+    http::read(stream, buffer, res);
+    
+    // Gracefully close the socket
+    beast::error_code ec;
+    stream.socket().shutdown(tcp::socket::shutdown_both, ec);
+    
+    // not_connected happens sometimes
+    // so don't bother reporting it.
+    //
+    if(ec && ec != beast::errc::not_connected)
+        throw beast::system_error{ec};
+    
+    // If we get here then the connection is closed gracefully
+    return boost::beast::buffers_to_string(res.body().data());
+}
+
+
+} // end of namespace pEp

webclient.hh

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <string>
+#include <stdexcept>
+
+namespace pEp
+{
+    class HttpError : public std::runtime_error
+    {
+    public:
+        HttpError(unsigned error_code, const std::string& error_message);
+    };
+
+
+    class Webclient
+    {
+    public:
+        Webclient(const std::string& server_name, unsigned port=80)
+        : m_server_name{server_name}
+        , m_port{port}
+        {}
+        
+        std::string get(const std::string& url);
+    
+    private:
+        const std::string& m_server_name;
+        const unsigned m_port;
+    };
+
+} // end of namespace pEp