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boost asio 學習(七) 網絡基礎 連接器和接收器(TCP示例)

本文轉載自   查看原文   2016-06-27 13:03   1653    asio/ boost/ c++代碼練習

http://www.gamedev.net/blog/950/entry-2249317-a-guide-to-getting-
started-with-boostasio?pg=8

7. Networking basics: connectors and acceptors (TCP)
我們來學習boost的TCP網絡編程。之前的篇章已經介紹了網絡系統框架。我們只需要學習網絡API函數即可

我們首先學習如何同步的連接主機。我們的代碼作為客戶端運行，使用tcp::socket對象.tcp::socket對象針對不同協議有不同的socket類型.我們需要確認使用正確的對象。當我們連接一個遠端主機
，我們需要獲得遠端的地址。為了達到這個目標，我們使用tcp::resolver。

#include <boost/asio.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/thread.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/bind.hpp>
#include <boost/lexical_cast.hpp>
#include <iostream>
#include <string>

boost::mutex global_stream_lock;

void WorkerThread( boost::shared_ptr< boost::asio::io_service > io_service )
{
	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Thread Start" << std::endl;
	global_stream_lock.unlock();

	while( true )
	{
		try
		{
			boost::system::error_code ec;
			io_service->run( ec );
			if( ec )
			{
				global_stream_lock.lock();
				std::cout << "[" << boost::this_thread::get_id()
					<< "] Error: " << ec << std::endl;
				global_stream_lock.unlock();
			}
			break;
		}
		catch( std::exception & ex )
		{
			global_stream_lock.lock();
			std::cout << "[" << boost::this_thread::get_id()
				<< "] Exception: " << ex.what() << std::endl;
			global_stream_lock.unlock();
		}
	}

	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Thread Finish" << std::endl;
	global_stream_lock.unlock();
}

int main( int argc, char * argv[] )
{
	boost::shared_ptr< boost::asio::io_service > io_service(
		new boost::asio::io_service
		);
	boost::shared_ptr< boost::asio::io_service::work > work(
		new boost::asio::io_service::work( *io_service )
		);
	boost::shared_ptr< boost::asio::io_service::strand > strand(
		new boost::asio::io_service::strand( *io_service )
		);

	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Press [return] to exit." << std::endl;
	global_stream_lock.unlock();

	boost::thread_group worker_threads;
	for( int x = 0; x < 2; ++x )
	{
		worker_threads.create_thread( boost::bind( &WorkerThread, io_service ) );
	}

	boost::asio::ip::tcp::socket sock( *io_service );

	try
	{
		boost::asio::ip::tcp::resolver resolver( *io_service );
		boost::asio::ip::tcp::resolver::query query( 
			"www.google.com", 
			boost::lexical_cast< std::string >( 80 )
			);
		boost::asio::ip::tcp::resolver::iterator iterator = resolver.resolve( query );
		boost::asio::ip::tcp::endpoint endpoint = *iterator;

		global_stream_lock.lock();
		std::cout << "Connecting to: " << endpoint << std::endl;
		global_stream_lock.unlock();

		sock.connect( endpoint );
	}
	catch( std::exception & ex )
	{
		global_stream_lock.lock();
		std::cout << "[" << boost::this_thread::get_id()
			<< "] Exception: " << ex.what() << std::endl;
		global_stream_lock.unlock();
	}

	std::cin.get();

	boost::system::error_code ec;
	sock.shutdown( boost::asio::ip::tcp::socket::shutdown_both, ec );
	sock.close( ec );

	io_service->stop();

	worker_threads.join_all();

	return 0;
}

　　

這個例子簡單的開啟了一個連接。程序將返回它實際嘗試連接的端口和IP。如果我們開啟一個命令提示窗口運行 "netstat -n",我們會看見這個程序的TCP連接
例子中我們使用query對象去重用這段代碼。代碼更適用於數字而不是字符串，所以我們使用函數將端口從數字轉化為字符串.

有時候我們可能需要異步的去連接一個遠程主機.例如GUI程序通過一個按鈕開啟連接，但是我們不希望GUI界面在連接完成之前就凍結住。boost::asio提供了一個異步連接方式。
使用bind shared_ptr。

#include <boost/asio.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/thread.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/bind.hpp>
#include <boost/lexical_cast.hpp>
#include <iostream>
#include <string>

boost::mutex global_stream_lock;

void WorkerThread( boost::shared_ptr< boost::asio::io_service > io_service )
{
	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Thread Start" << std::endl;
	global_stream_lock.unlock();

	while( true )
	{
		try
		{
			boost::system::error_code ec;
			io_service->run( ec );
			if( ec )
			{
				global_stream_lock.lock();
				std::cout << "[" << boost::this_thread::get_id()
					<< "] Error: " << ec << std::endl;
				global_stream_lock.unlock();
			}
			break;
		}
		catch( std::exception & ex )
		{
			global_stream_lock.lock();
			std::cout << "[" << boost::this_thread::get_id()
				<< "] Exception: " << ex.what() << std::endl;
			global_stream_lock.unlock();
		}
	}

	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Thread Finish" << std::endl;
	global_stream_lock.unlock();
}

void OnConnect( const boost::system::error_code & ec, boost::shared_ptr< boost::asio::ip::tcp::socket > sock )
{
	if( ec )
	{
		global_stream_lock.lock();
		std::cout << "[" << boost::this_thread::get_id()
			<< "] Error: " << ec << std::endl;
		global_stream_lock.unlock();
	}
	else
	{
		global_stream_lock.lock();
		std::cout << "[" << boost::this_thread::get_id()
			<< "] Connected!" << std::endl;
		global_stream_lock.unlock();
	}
}

int main( int argc, char * argv[] )
{
	boost::shared_ptr< boost::asio::io_service > io_service(
		new boost::asio::io_service
		);
	boost::shared_ptr< boost::asio::io_service::work > work(
		new boost::asio::io_service::work( *io_service )
		);
	boost::shared_ptr< boost::asio::io_service::strand > strand(
		new boost::asio::io_service::strand( *io_service )
		);

	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Press [return] to exit." << std::endl;
	global_stream_lock.unlock();

	boost::thread_group worker_threads;
	for( int x = 0; x < 2; ++x )
	{
		worker_threads.create_thread( boost::bind( &WorkerThread, io_service ) );
	}

	boost::shared_ptr< boost::asio::ip::tcp::socket > sock(
		new boost::asio::ip::tcp::socket( *io_service )
		);

	try
	{
		boost::asio::ip::tcp::resolver resolver( *io_service );
		boost::asio::ip::tcp::resolver::query query( 
			"www.google.com", 
			boost::lexical_cast< std::string >( 80 )
			);
		boost::asio::ip::tcp::resolver::iterator iterator = resolver.resolve( query );
		boost::asio::ip::tcp::endpoint endpoint = *iterator;

		global_stream_lock.lock();
		std::cout << "Connecting to: " << endpoint << std::endl;
		global_stream_lock.unlock();

		sock->async_connect( endpoint, boost::bind( OnConnect, _1, sock ) );
	}
	catch( std::exception & ex )
	{
		global_stream_lock.lock();
		std::cout << "[" << boost::this_thread::get_id()
			<< "] Exception: " << ex.what() << std::endl;
		global_stream_lock.unlock();
	}

	std::cin.get();

	boost::system::error_code ec;
	sock->shutdown( boost::asio::ip::tcp::socket::shutdown_both, ec );
	sock->close( ec );

	io_service->stop();

	worker_threads.join_all();

	return 0;
}

　　

如果想傳遞boost::asio對象，我們一般使用shared_ptr智能指針.因為大多數對象是不能拷貝的non-copyable,並且我們確定對象在等待調用期間依然有效。
我們使用bind設置我們的自定義處理程序。
最后一個例子我們異步連接遠端地址

#include <boost/asio.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/thread.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/bind.hpp>
#include <boost/lexical_cast.hpp>
#include <iostream>
#include <string>

boost::mutex global_stream_lock;

void WorkerThread( boost::shared_ptr< boost::asio::io_service > io_service )
{
	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Thread Start" << std::endl;
	global_stream_lock.unlock();

	while( true )
	{
		try
		{
			boost::system::error_code ec;
			io_service->run( ec );
			if( ec )
			{
				global_stream_lock.lock();
				std::cout << "[" << boost::this_thread::get_id()
					<< "] Error: " << ec << std::endl;
				global_stream_lock.unlock();
			}
			break;
		}
		catch( std::exception & ex )
		{
			global_stream_lock.lock();
			std::cout << "[" << boost::this_thread::get_id()
				<< "] Exception: " << ex.what() << std::endl;
			global_stream_lock.unlock();
		}
	}

	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Thread Finish" << std::endl;
	global_stream_lock.unlock();
}

void OnAccept( const boost::system::error_code & ec, boost::shared_ptr< boost::asio::ip::tcp::socket > sock )
{
	if( ec )
	{
		global_stream_lock.lock();
		std::cout << "[" << boost::this_thread::get_id()
			<< "] Error: " << ec << std::endl;
		global_stream_lock.unlock();
	}
	else
	{
		global_stream_lock.lock();
		std::cout << "[" << boost::this_thread::get_id()
			<< "] Accepted!" << std::endl;
		global_stream_lock.unlock();
	}
}

int main( int argc, char * argv[] )
{
	boost::shared_ptr< boost::asio::io_service > io_service(
		new boost::asio::io_service
		);
	boost::shared_ptr< boost::asio::io_service::work > work(
		new boost::asio::io_service::work( *io_service )
		);
	boost::shared_ptr< boost::asio::io_service::strand > strand(
		new boost::asio::io_service::strand( *io_service )
		);

	global_stream_lock.lock();
	std::cout << "[" << boost::this_thread::get_id()
		<< "] Press [return] to exit." << std::endl;
	global_stream_lock.unlock();

	boost::thread_group worker_threads;
	for( int x = 0; x < 2; ++x )
	{
		worker_threads.create_thread( boost::bind( &WorkerThread, io_service ) );
	}

	boost::shared_ptr< boost::asio::ip::tcp::acceptor > acceptor(
		new boost::asio::ip::tcp::acceptor( *io_service )
		);
	boost::shared_ptr< boost::asio::ip::tcp::socket > sock(
		new boost::asio::ip::tcp::socket( *io_service )
		);

	try
	{
		boost::asio::ip::tcp::resolver resolver( *io_service );
		boost::asio::ip::tcp::resolver::query query( 
			"127.0.0.1", 
			boost::lexical_cast< std::string >( 7777 )
			);
		boost::asio::ip::tcp::endpoint endpoint = *resolver.resolve( query );
		acceptor->open( endpoint.protocol() );
		acceptor->set_option( boost::asio::ip::tcp::acceptor::reuse_address( false ) );
		acceptor->bind( endpoint );
		acceptor->listen( boost::asio::socket_base::max_connections );
		acceptor->async_accept( *sock, boost::bind( OnAccept, _1, sock ) );

		global_stream_lock.lock();
		std::cout << "Listening on: " << endpoint << std::endl;
		global_stream_lock.unlock();
	}
	catch( std::exception & ex )
	{
		global_stream_lock.lock();
		std::cout << "[" << boost::this_thread::get_id()
			<< "] Exception: " << ex.what() << std::endl;
		global_stream_lock.unlock();
	}

	std::cin.get();

	boost::system::error_code ec;
	acceptor->close( ec );

	sock->shutdown( boost::asio::ip::tcp::socket::shutdown_both, ec );
	sock->close( ec );

	io_service->stop();

	worker_threads.join_all();

	return 0;
}

　　

這個例子與上一個例子很類似。事實上僅僅有一點點改變。之前提到過，asio庫是一個很優秀的庫。我們學習他的一些組件，就能理解它的其他組件。
在端口7777上運行上面這段代碼，我們可以從命令行窗口運行命令"telnet localhost 7777"，開啟一個到服務器的連接來激發代碼中的 OnAccept函數

然而服務器將不能再接收更多的連接，這是因為我們僅僅只呼叫了async_accept一次並且只有一個socket 對象。稍后我們將處理服務器的設計策略。我們僅僅只是需要開啟核心API。
例子中，我們使用錯誤變量來確認沒有異常發生。
討論完基本的連接和接收。下章節將討論socket的讀寫


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