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c++ - 如何使用 Boost::Asio 访问网络服务?

转载 作者:塔克拉玛干 更新时间:2023-11-02 20:32:52 25 4
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我想知道是否有可能使用 boost asio 库访问 Web 服务。

我尝试了以下从 boost asio 文档中获得的代码(在 IOS、C++11 中)。但它抛出以下内容。

try
{
boost::asio::io_service io_service;
std::string address = "http://www.thomas-bayer.com/axis2/services/BLZService/";

// Get a list of endpoints corresponding to the server name.
tcp::resolver resolver(io_service);
tcp::resolver::query query(address,boost::asio::ip::resolver_query_base::numeric_service);


tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);

endpoint_iterator->host_name() = "www.thomas-bayer.com/axis2/services/BLZService/";

std::cout<<"Print Query --"<<std::endl;

// Try each endpoint until we successfully establish a connection.
tcp::socket socket(io_service);

boost::asio::connect(socket, endpoint_iterator);

// Form the request. We specify the "Connection: close" header so that the
// server will close the socket after transmitting the response. This will
// allow us to treat all data up until the EOF as the content.
boost::asio::streambuf request;
std::ostream request_stream(&request);
request_stream << "POST: HTTP/1.0\r\n";
request_stream << "Host: " << address << "\r\n";
request_stream << "Accept: */*\r\n";
request_stream << "Connection: close\r\n\r\n";

// Send the request.
boost::asio::write(socket, request);

// Read the response status line. The response streambuf will automatically
// grow to accommodate the entire line. The growth may be limited by passing
// a maximum size to the streambuf constructor.

boost::asio::streambuf response;
boost::asio::read_until(socket, response, "\r\n");

// Check that response is OK.
std::istream response_stream(&response);
std::string http_version;
response_stream >> http_version;
unsigned int status_code;
response_stream >> status_code;
std::string status_message;
std::getline(response_stream, status_message);

if (!response_stream || http_version.substr(0, 5) != "HTTP/")
{
std::cout << "Invalid response\n";
return;
}
if (status_code != 200)
{
std::cout << "Response returned with status code " << status_code << "\n";
return;
}

// Read the response headers, which are terminated by a blank line.
boost::asio::read_until(socket, response, "\r\n\r\n");

// Process the response headers.
std::string header;
while (std::getline(response_stream, header) && header != "\r")
std::cout << header << "\n";
std::cout << "\n";

// Write whatever content we already have to output.
if (response.size() > 0)
std::cout << &response;

// Read until EOF, writing data to output as we go.
boost::system::error_code error;
while (boost::asio::read(socket, response,
boost::asio::transfer_at_least(1), error))
std::cout << &response;
if (error != boost::asio::error::eof)
throw boost::system::system_error(error);
}
catch (std::exception& e)
{
std::cout << "Exception: " << e.what() << "\n";
}

Exception: connect: Can't assign requested address

或者

Exception: resolve: Host not found (authoritative)

代码有什么问题?还是我做的完全错了?

谢谢

最佳答案

名称解析失败,因为您混淆了请求、URL、协议(protocol)、主机名和 IP 地址。

FQDN 上执行请求.除非您知道,否则您需要提供服务。本例中的服务遵循协议(protocol)¹,`http://通常在端口 80 上提供服务:

std::string const address = "www.thomas-bayer.com";
tcp::resolver::query query(address, "80", boost::asio::ip::resolver_query_base::numeric_service);

请注意,在大多数系统上,您可以等效地使用:

std::string const address = "www.thomas-bayer.com";
tcp::resolver::query query(address, "http");

查看 http://www.thomas-bayer.com 部分去了哪里?

现在 /axis2/services/BLZService/ 是查询路径,就像您在 GET 请求中写的那样:

request_stream << "GET /axis2/services/BLZService/ HTTP/1.1\r\n";

注意事项:

  1. POST 不是 header (所以没有冒号!)它是 HTTP“动词”(GET、POST、DELETE、PUT...)
  2. “主机” header 主机名:

     request_stream << "Host: " << address << "\r\n";

    是正确的 iff address 确实是主机的逻辑名称

  3. 像这样设置主机名:

     endpoint_iterator->host_name() = "www.thomas-bayer.com/axis2/services/BLZService/";

    是我以前从未见过的东西,我不确定它应该实现什么。也许只是错了?

¹ 按照惯例,它可以是其他

修复

#include <boost/asio.hpp>
#include <iostream>
using boost::asio::ip::tcp;

void test() try {
boost::asio::io_service io_service;
std::string const address = "www.thomas-bayer.com";

// Get a list of endpoints corresponding to the server name.
tcp::resolver resolver(io_service);
tcp::resolver::query query(address, "80", boost::asio::ip::resolver_query_base::numeric_service);

tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);

std::cout << "Print Query --" << std::endl;

// Try each endpoint until we successfully establish a connection.
tcp::socket socket(io_service);

boost::asio::connect(socket, endpoint_iterator);

// Form the request. We specify the "Connection: close" header so that the
// server will close the socket after transmitting the response. This will
// allow us to treat all data up until the EOF as the content.
boost::asio::streambuf request;
std::ostream request_stream(&request);
request_stream << "GET /axis2/services/BLZService HTTP/1.0\r\n";
request_stream << "Host: " << address << "\r\n";
request_stream << "Accept: */*\r\n";
request_stream << "Connection: close\r\n\r\n";

// Send the request.
boost::asio::write(socket, request);

// Read the response status line. The response streambuf will automatically
// grow to accommodate the entire line. The growth may be limited by
// passing a maximum size to the streambuf constructor.
boost::asio::streambuf response;
boost::asio::read_until(socket, response, "\r\n");

// Check that response is OK.
std::istream response_stream(&response);
std::string http_version, status_message;
unsigned int status_code;
std::getline(response_stream >> http_version >> status_code, status_message);

if (!response_stream || http_version.substr(0, 5) != "HTTP/") {
std::cout << "Invalid response\n";
return;
}
if (status_code != 200) {
std::cout << "Response returned with status code " << status_code << "\n";
return;
}

// Read the response headers, which are terminated by a blank line.
boost::asio::read_until(socket, response, "\r\n\r\n");

// Process the response headers.
std::string header;
while (std::getline(response_stream, header) && header != "\r")
std::cout << header << "\n";
std::cout << "\n";

// Write whatever content we already have to output.
if (response.size() > 0)
std::cout << &response;

// Read until EOF, writing data to output as we go.
boost::system::error_code error;
while (boost::asio::read(socket, response, boost::asio::transfer_at_least(1), error))
std::cout << &response;
if (error != boost::asio::error::eof)
throw boost::system::system_error(error);
} catch (std::exception &e) {
std::cout << "Exception: " << e.what() << "\n";
}

int main() { test(); }

关于c++ - 如何使用 Boost::Asio 访问网络服务?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/44386919/

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