如何使用 boost 库获取谷歌海拔 api？答案

【问题标题】：How to get google elevation api with boost library?如何使用 boost 库获取谷歌海拔 api？
【发布时间】：2021-04-10 01:56:46
【问题描述】：

*环境 C++ 11 提升 1.73

我关注了https://www.boost.org/doc/libs/1_70_0/libs/beast/doc/html/beast/quick_start/http_client.html的例子。

从自己的Http Server获取数据就成功了（我是说本地127.0.0.1）

但是我无法通过这个例子从谷歌海拔 api 获取数据。

我的“get”函数是。

json HttpClient::GET(std::string host, std::string port, std::string target)
{
    njson result = njson::object();
    result["state"] = "F";

    try{
        // 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(host, 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, target, HTTP_VERSION };
        req.set(http::field::host, host);
        req.set(http::field::user_agent, BOOST_BEAST_VERSION_STRING);

        // 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);

        // Write the message to standard out
        std::string sstr = boost::beast::buffers_to_string(res.body().data());
        
        result = njson::parse(sstr);
    
        // 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
    }
    catch (std::exception const& e)
    {
        std::cerr << "Error: " << e.what() << std::endl;
    }
    return result;
}

这是我的主要内容

// Performs an HTTP GET and prints the response
int main(int argc, char** argv)
{
    auto const host = "https://maps.googleapis.com";
    auto const port = "443";
    auto const target = "/maps/api/elevation/json?locations=39.7391536,-104.9847034&key=MY_KEY";

    json res = HttpClient::GET(host,port, target);
    std::cout << "***********************" << std::endl;
    std::cout << res.dump() << std::endl;
    return 0;
}

但结果是。 Resolve: no such host is known

当我编写该代码时，它会执行 catch 语句。

auto const results = resolver.resolve(host, port);

我认为我的一个参数是错误的。但我没有任何想法。我该怎么办？

【问题讨论】：

标签： c++ boost httpclient resolver

【解决方案1】：

删除主机名中的“https://”。它工作得很好。但是...我现在有一个“错误：流结束”消息。

【讨论】：