使用BOOST实现简单的HTTP网页下载

bool httpGet(/*out*/string& result, const string& host, uint16_t port, const string& url,boost::asio::io_service &_io)
{
try
{
string domain = host;
boost::asio::ip::tcp::resolver resolver(_io);
boost::asio::ip::tcp::resolver_query query(domain, IntToStr(port));
boost::asio::ip::tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
boost::asio::ip::tcp::resolver::iterator end;

//Try each endpoint until we successfully establish a connection.
boost::asio::ip::tcp::socket socket(_io);
boost::system::error_code error = boost::asio::error::host_not_found;
while (error && endpoint_iterator != end)
{
socket.close();
socket.connect(*endpoint_iterator++, error);
}
if (error)
throw boost::system::system_error(error);

//// 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 " << url
<< " HTTP/1.0\r\n";
request_stream << "Host: " << socket.remote_endpoint().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.
boost::asio::streambuf response(4096);
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::cerr << "[Get Address ]: Invalid response\n";
return false;
}
if (status_code != 200)
{
std::cerr << "[Get Address ]: Response returned with status code " << status_code << "\n";
return false;
}

// 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"){
}

// Read until EOF, writing data to output as we go.
while (boost::asio::read(socket, response,
boost::asio::transfer_at_least(1), error)) {
;
}

string temp;
while(!response_stream.eof()){
std::getline(response_stream, temp);
result.append(temp);
}

if (error != boost::asio::error::eof)
throw boost::system::system_error(error);

return true;
}catch(std::excetion& e){std::cerr << e.what();}

return false;
}