使用boost::asio实现客户端的异步通讯访问pop3服务器。
#include <iostream>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
using namespace std;
using boost::asio::ip::tcp;
#define MAIL_SERVER "pop3.m.com" // 邮件服务器域名
// pop3命令
#define CMD_USER "user myuser\n"
#define CMD_PASS "pass mypass\n"
#define CMD_QUIT "quit\n"
// 接收缓存
#define RECV_BUFFER_SIZE 1024
// 异步socket事件处理类
class async_socket_handler
{
private:
tcp::socket &m_sock; // boost tcp socket
string m_status; // 执行状态
char m_buffer_1[RECV_BUFFER_SIZE]; // 消息接收缓存
public:
async_socket_handler(tcp::socket &sock) : m_sock(sock), m_status("closed")
{
return;
}
// 当连接完成后，执行该方法
void on_connected(const boost::system::error_code& error)
{
if ( error == 0 ) {
// 连接成功，打印消息，
cout<<"info: connection has been established"<<endl;
m_status = "connected";
// 接收服务器欢迎消息，消息收到后，触发on_message_arrival消息执行
m_sock.async_read_some(boost::asio::buffer(m_buffer_1, RECV_BUFFER_SIZE),
boost::bind(&async_socket_handler::on_message_arrival,
this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
} else {
cout<<"error: failed to connect remote: "<<error<<endl;
}
} // end of on_connected
// 命令消息发送异步事件处理方法，当命令发送完成后，将执行该方法。
void on_message_sent(const boost::system::error_code& error, size_t size)
{
if ( error == 0 ) {
cout<<"info: "<<m_status<<", "<<size<<" bytes sent"<<endl;
// 命令消息发送成功后，立即准备收消息，消息收到后，触发on_message_arrival消息执行
m_sock.async_read_some(boost::asio::buffer(m_buffer_1, RECV_BUFFER_SIZE),
boost::bind(&async_socket_handler::on_message_arrival,
this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
} else {
cout<<"error: "<<m_status<<" failed: "<<error<<endl;
}
}
// 收到远程返回的消息后, 此事件方法将被调用。
void on_message_arrival(const boost::system::error_code& error, size_t size)
{
if ( error ) {
cout<<"error: receive message failed, "<<error<<endl;
return ;
}
// 参数size表示收到的字节数，收到的消息位于m_buffer_1
m_buffer_1[size] = ‘\0‘;
cout<<m_buffer_1<<endl;
// 收消息成功，根据不同的状态分别处理
if ( m_status == string("connected")) {
// 连接后，收到服务器欢迎消息，发送用户登录命令
m_status = string("username_sent");
cout<<"begin send user name"<<endl;
m_sock.async_write_some(boost::asio::buffer(CMD_USER, strlen(CMD_USER)),
boost::bind(&async_socket_handler::on_message_sent,
this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
} else if (m_status == string("username_sent")) {
// 收到服务器用户名确认消息，接着发送口令命令
m_status = "password_sent";
cout<<"begin send password"<<endl;
m_sock.async_write_some(boost::asio::buffer(CMD_PASS, strlen(CMD_PASS)),
boost::bind(&async_socket_handler::on_message_sent,
this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
} else if (m_status == string("password_sent")) {
// 发送quit命令
m_status = "quit_sent";
cout<<"begin send quit"<<endl;
m_sock.async_write_some(boost::asio::buffer(CMD_QUIT, strlen(CMD_QUIT)),
boost::bind(&async_socket_handler::on_message_sent,
this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
return ;
}
};
int main()
{
boost::asio::io_service ioservice;
tcp::socket socket(ioservice);
tcp::endpoint endpoint;
boost::system::error_code errcode;
tcp::resolver resolver(ioservice);
tcp::resolver::iterator iter_endpoint, iter_null;
tcp::resolver::query query(MAIL_SERVER, "pop3");
async_socket_handler handler(socket); // 处理socket异步事件回调
// 域名解析
iter_endpoint = resolver.resolve(query, errcode);
endpoint = iter_endpoint->endpoint();
try {
// 首先执行异步连接，此后的操作在async_socket_handler中
// 根据不同的命令状态一次完成。
socket.async_connect(endpoint,
boost::bind(&async_socket_handler::on_connected,
&handler,
boost::asio::placeholders::error));
ioservice.run(); // 启动异步io过程
cout<<"io service running finished"<<endl;
socket.close(); // 通讯过程完成后，关闭socket
} catch (const boost::system::system_error& e) {
cout<<"connect error: "<<e.what()<<endl;
}
return 0;
} // end of main
原文：http://my.oschina.net/luckysym/blog/469317