我真的愿意为我的C ++应用程序学习boost :: asio。 所以我开始使用＆＃34;简单＆＃34;在我的笔记本电脑上编译和运行的客户端应用程序。这个想法非常简单。客户端启动与服务器的连接，并每2秒询问一次答案。我有可能触发服务器＆＃39;状态（假设发出警报信号）。作为反应，当客户端尝试连接到服务器时，后者将通知它我必须准备好接收一些数据（具有一些双重和整数值的列表）。客户端询问列表，服务器通过连接发送所需列表。
问题：列表未完全传输。列表的一大块将被发送并被正确接收，但之后我不再收到任何数据。
由于我将应用程序拆分为类，因此代码为：
client.h
#include <iostream>
#include <string>
#include <sstream>
#include <fstream>
#include <ostream>
#include <chrono>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/array.hpp>
#include <boost/regex.hpp>
#include <boost/lexical_cast.hpp>
#include <boost/asio/io_service.hpp>
#include <boost/asio/write.hpp>
#include <boost/asio/buffer.hpp>
#include <boost/asio/ip/tcp.hpp>
#ifndef __CLIENT_CLASS__
#define __CLIENT_CLASS__
//#define DEBUG
class Client
{
boost::asio::io_service io_service_;
boost::asio::ip::tcp::resolver resolver_{ io_service_ };
boost::asio::ip::tcp::socket socket_{ io_service_ };
boost::asio::streambuf request_;
boost::asio::streambuf response_;
const std::string host_server_;
const std::string port_;
const uint uiId_;
const long double dLon_;
const long double dLat_;
const double dHeight_;
const std::string useragent_ = "HTMLGET 1.0";
enum State { STANDBY = 0x01,
ALARM = 0x02,
WPL_REC = 0x04 };
State state_ = STANDBY;
std::chrono::milliseconds server_response_delay_ = std::chrono::milliseconds( 2000 ); // SERVER_RESPONSE_DELAY
uint uiError_ = 0;
bool bAlarmFlag_;
unsigned int uiRequestCounter_;
std::chrono::high_resolution_clock::time_point begin_time_;
public:
explicit Client( const std::string &address, const std::string &port, uint id,
long double start_longitude, long double start_latitude,
double start_height );
virtual ~Client();
void run( void );
std::chrono::milliseconds getServerResponseDelay( void ) const;
void setServerResponseDelay( std::chrono::milliseconds milliseconds );
private:
void buildQuery( void );
void handleResolve( const boost::system::error_code &ec, boost::asio::ip::tcp::resolver::iterator it );
void handleConnect( const boost::system::error_code &ec );
void handleWriteRequest( const boost::system::error_code &ec );
void handleReadStatusLine( const boost::system::error_code &ec );
void handleMessage( const boost::system::error_code &error_msg );
void readContent( const boost::system::error_code &error_msg );
void build_wpl_query( void );
std::string build_ok_answer( void );
std::string build_alarm_answer( void );
std::string build_wpl_answer( void );
};
#endif
我的 client.cpp 。我在问题所在的位置放了一行评论。
#include "client.h"
Client::Client( const std::string &address, const std::string &port, uint id,
long double start_longitude, long double start_latitude,
double start_height ) : host_server_( address ), port_( port ),
uiId_(id), dLon_( start_longitude ), dLat_( start_latitude ), dHeight_( start_height )
{
std::cout << "Constructor of the class \"Client\" called" << std::endl;
bAlarmFlag_ = false;
uiRequestCounter_ = 1;
begin_time_ = std::chrono::high_resolution_clock::now();
}
Client::~Client()
{
std::cout << "Destructor of the class \"Client\" called" << std::endl;
}
void Client::run( void )
{
if( std::chrono::duration_cast<std::chrono::milliseconds>( std::chrono::high_resolution_clock::now() - begin_time_ ) > server_response_delay_ )
{
begin_time_ = std::chrono::high_resolution_clock::now();
boost::asio::ip::tcp::resolver::query local_query( host_server_, port_ );
resolver_.async_resolve( local_query, boost::bind( &Client::handleResolve, this, boost::asio::placeholders::error, boost::asio::placeholders::iterator ) );
size_t service_status = io_service_.run();
std::cout << "IO Service status: " << service_status << std::endl << std::endl;
io_service_.reset();
}
}
void Client::handleResolve( const boost::system::error_code &error_msg, boost::asio::ip::tcp::resolver::iterator it )
{
if( !error_msg ) {
boost::asio::async_connect( socket_, it, boost::bind( &Client::handleConnect, this, boost::asio::placeholders::error ) );
} else {
std::cout << "Handle Resolv Error: " << error_msg.message() << std::endl;
}
}
void Client::handleConnect( const boost::system::error_code &error_msg )
{
if( !error_msg ) {
std::cout << "-------------------------------------------------------------------------------";
std::cout << std::endl << "Request Nr: " << (int)uiRequestCounter_ << std::endl;
std::cout << "Socket created" << std::endl;
if( !bAlarmFlag_ )
buildQuery();
if( bAlarmFlag_ ) {
build_wpl_query();
bAlarmFlag_ = false;
}
boost::asio::async_write( socket_, request_, boost::bind( &Client::handleWriteRequest, this, boost::asio::placeholders::error ) );
++uiRequestCounter_;
} else {
std::cout << "Handle Connect Error: " << error_msg.message() << std::endl;
}
}
void Client::handleWriteRequest( const boost::system::error_code &error_msg )
{
std::cout << "Waiting answer from Server..." << std::endl;
if( !error_msg ) {
boost::asio::async_read_until( socket_, response_, "\r\n", boost::bind( &Client::handleReadStatusLine, this, boost::asio::placeholders::error ) );
} else {
std::cout << "Handle Write Request Error: " << error_msg.message() << std::endl;
}
}
void Client::handleReadStatusLine( const boost::system::error_code &error_msg )
{
std::string header_string;
unsigned int status_code;
std::string server_status;
if( !error_msg ) {
std::istream response_stream( &response_ );
response_stream >> header_string;
response_stream >> status_code;
response_stream >> server_status;
std::cout << std::endl << header_string << " " << status_code << " " << server_status << std::endl;
if( header_string.substr(0, 8) != "HTTP/1.1" ) {
std::cout << "Not a valid message from Server" << std::endl;
return;
}
if( status_code != 200 ) {
std::cout << "Code 200 not available from Server" << std::endl;
return;
}
if( server_status != "OK" ) {
std::cout << "Not a OK message from Server" << std::endl;
return;
}
if( ( header_string.substr(0, 8) == "HTTP/1.1" ) && ( status_code == 200 ) && ( server_status == "OK" ) ) {
std::cout << "Server OK, start retrieving data" << std::endl;
boost::asio::async_read_until( socket_, response_, "\r\n\r\n", boost::bind( &Client::handleMessage, this, boost::asio::placeholders::error ) );
} else {
std::cout << "Not a valid packet from Server" << std::endl;
}
} else {
std::cout << "Handle Read Status Line Error: " << error_msg.message() << std::endl;
}
}
void Client::handleMessage( const boost::system::error_code &error_msg )
{
if( !error_msg ) {
std::istream response_stream( &response_ );
std::string header_string;
while( std::getline( response_stream, header_string ) && header_string != "\r\n" ) {
// http://stackoverflow.com/a/30083146
/* if( static_cast<int>( header_string.find( "Content-Length:" ) ) != -1 ) {
std::string car = boost::regex_replace( header_string, boost::regex( "[^0-9]*([0-9]+).*" ), std::string( "\\1" ) );
std::cout << "Content-Length: " << std::stoi( car ) << std::endl;
}*/
if( header_string.find( build_ok_answer() ) != std::string::npos ) {
bAlarmFlag_ = false;
std::cout << "I received a \033[1;32mALIVE-Signal\033[0m from the Server." << std::endl;
} else if( header_string.find( build_alarm_answer() ) != std::string::npos ) {
bAlarmFlag_ = true;
std::cout << "I received a \033[1;31mALARM-Signal\033[0m from Server!" << std::endl;
} else if( header_string.find( build_wpl_answer() ) != std::string::npos ) {
std::cout << std::endl << "List \033[1;34mData\033[0m received." << std::endl;
/* HERE I READ A BLOCK OF THE LIST BUT NOT THE WHOLE LIST!!!! */
std::cout << &response_;
}
}
boost::asio::async_read( socket_, response_, boost::asio::transfer_at_least(1),
boost::bind(&Client::readContent, this, boost::asio::placeholders::error ) );
} else {
std::cout << "Handle Message Error: " << error_msg.message() << std::endl;
}
}
void Client::readContent( const boost::system::error_code &error_msg )
{
if( !error_msg ) {
/* Read until the EOF */
boost::asio::async_read( socket_, response_, boost::asio::transfer_at_least(1),
boost::bind( &Client::readContent, this, boost::asio::placeholders::error ) );
} else if ( error_msg != boost::asio::error::eof ) {
std::cout << "Read Content Error: " << error_msg.message() << std::endl;
}
}
void Client::buildQuery( void )
{
std::ostream ssRequest( &request_ );
ssRequest << "GET /api/rest/v1/register?";
ssRequest << "id=" << uiId_ << '&' << "delay=" << ( static_cast<int>(server_response_delay_.count()) ) << '&' << "lon=" << dLon_ << '&';
ssRequest << "lat=" << dLat_ << '&' << "height=" << dHeight_ << '&' << "state=" << state_ << '&' << "error=" << uiError_;
ssRequest << " HTTP/1.0\r\nHost: " << host_server_ << "\r\nUser-Agent: " << useragent_ << "\r\n\r\n";
}
std::string Client::build_ok_answer( void )
{
std::ostringstream ssAnswerOk;
ssAnswerOk << "{\"Text\":\"OK\",\"Id\":" << uiId_ << "}";
return ssAnswerOk.str();
}
std::string Client::build_alarm_answer( void )
{
std::ostringstream ssAnswerAlarm;
ssAnswerAlarm << "{\"Text\":\"ALARM\",\"Id\":" << uiId_ << "}";
return ssAnswerAlarm.str();
}
std::string Client::build_wpl_answer( void )
{
std::ostringstream ssAnswerWpl;
ssAnswerWpl << "QGC WPL 120";
return ssAnswerWpl.str();
}
std::chrono::milliseconds Client::getServerResponseDelay( void ) const
{
return server_response_delay_;
}
void Client::build_wpl_query( void )
{
std::ostream ssRequestWpl( &request_ );
ssRequestWpl << "GET /File/data" << uiId_ << ".txt";
ssRequestWpl << " HTTP/1.0\r\nHost: " << host_server_ << "\r\nUser-Agent: " << useragent_ << "\r\n\r\n";
}
现在......我受到了激励website上的例子的启发。如果我启动程序，它会开始每隔2秒向服务器询问一次。 我收到了正确答案：
Constructor of the class "Client" called
-----------------------------------
Request Nr: 1 Socket created Waiting answer from Server...
HTTP/1.1 200 OK
Server OK, start retrieving data
I received a ALIVE-Signal from the Server.
IO Service status: 6
------------------------------------
Request Nr: 2 Socket created Waiting answer from Server...
HTTP/1.1 200 OK
Server OK, start retrieving data
I received a ALIVE-Signal from the Server.
IO Service status: 6
------------------------------------
Request Nr: 3 Socket created Waiting answer from Server...
HTTP/1.1 200 OK
Server OK, start retrieving data
I received a ALIVE-Signal from the Server.
IO Service status: 6
------------------------------------
但是，就我开始请求列表而言，我收到以下内容：
Request Nr: 6
Socket created
Waiting answer from Server...
HTTP/1.1 200 OK
Server OK, start retrieving data
List Data received.
0 1 3 22 1 1000 1 3 51.9896769729347099 8.62269043922424316 35 1 0
1 0 3 16 1 1000 3 1 51.9908133374338917 8.6260378360748291 0 1 0
2 0 3 16 1 5000 3 1 51.9903706872495235 8.62733602523803711 -30 1 1
3 0 3 16 1 1000 3 1 51.9906
IO Service status: 7
这不是真正的整个列表。 该列表还有几行：
0 1 3 22 1 1000 1 3 231.9896769729347099 83.62269043922424316 35 1 0
1 0 3 16 1 1000 3 1 221.9908133374338917 82.6260378360748291 0 1 0
2 0 3 16 1 5000 3 1 121.9903706872495235 84.62733602523803711 -30 1 1
3 0 3 16 1 1000 3 1 45.99066872495235564
82.62733602523803711 -30 1 1 2 0 3 16 1 5000 3 1 124.9903706872495235 24.62733602324442711 -30 1 1 3 0 3 16 1 1000 3 1 22.99066872495235564 22.62235353533535351 -30 1 1
在我看来，连接（也许我错了）突然被打破了。然后它从头开始，它接收剩余的行。 但我需要立刻收到整个清单。 有什么问题？
编辑：非常感谢rhashimoto。我帮助了解了很多事情以及可以改进的内容。 他的回答并没有解决问题。因为，如果我这样做：
void Client::run( void )
{
if( std::chrono::duration_cast<std::chrono::milliseconds>( std::chrono::high_resolution_clock::now() - begin_time_ ) > server_response_delay_ )
{
begin_time_ = std::chrono::high_resolution_clock::now();
boost::asio::ip::tcp::resolver::query local_query( host_server_, port_ );
resolver_.async_resolve( local_query, boost::bind( &Client::handleResolve, this, boost::asio::placeholders::error, boost::asio::placeholders::iterator ) );
size_t service_status = io_service_.run();
if( flag_ ) {
list << &response_;
std::cout << list.str();
}
std::cout << "IO Service status: " << service_status << std::endl << std::endl;
io_service_.reset();
}
}
（当我请求列表时， flag 只设置一次），然后我收到列表的第二部分但不是第一部分。
有什么想法吗？
如果我在没有标志变量的情况下放置该行，那么连接就会停留在该点并且不会显示任何内容。
答案 0 :(得分：2)
您的async_read*处理程序缺少bytes_transferred参数。他们应该有signature：
void handler(
const boost::system::error_code& error, // Result of operation.
std::size_t bytes_transferred // Number of bytes copied into the
// buffers. If an error occurred,
// this will be the number of
// bytes successfully transferred
// prior to the error.
);
请注意，您还需要在绑定它们的任何位置添加占位符参数。
但是，对于你的问题，这不是问题所在。问题是您在阅读之前打印出响应正文。请注意这一行：/* HERE I READ A BLOCK OF THE LIST BUT NOT THE WHOLE LIST!!!! */
std::cout << &response_;
在此行之前执行：
boost::asio::async_read( socket_, response_, boost::asio::transfer_at_least(1),
boost::bind(&Client::readContent, this, boost::asio::placeholders::error ) );
好的，现在你可能想知道在阅读它之前是否可以打印任何身体。答案是您使用async_read_until来读取HTTP状态行和所有标头。文档说明：
成功执行async_read_until操作后，streambuf可以 包含分隔符之外的其他数据。申请将 通常将该数据留在streambuf中以供后续使用 要检查的async_read_until操作。
因此，您要打印出您未使用std::istream消费的其他数据。这恰好是您列表的第一部分。然后你继续阅读其余内容，但是你不打印出来，所以它只是放在streambuf（你在下一个请求中看到它）。
在
读取完成后，尝试将std::cout行移至Client::run()，。：
void Client::run( void )
{
if( std::chrono::duration_cast<std::chrono::milliseconds>( std::chrono::high_resolution_clock::now() - begin_time_ ) > server_response_delay_ )
{
begin_time_ = std::chrono::high_resolution_clock::now();
boost::asio::ip::tcp::resolver::query local_query( host_server_, port_ );
resolver_.async_resolve( local_query, boost::bind( &Client::handleResolve, this, boost::asio::placeholders::error, boost::asio::placeholders::iterator ) );
size_t service_status = io_service_.run();
// ******************************
// ***** MOVE PRINT TO HERE *****
// ******************************
std::cout << &response_;
std::cout << "IO Service status: " << service_status << std::endl << std::endl;
io_service_.reset();
}
}
或者您可以放在Client::readContent()的顶部（如果可以将其打印出来）。