python - asio 无法将消息写入服务器两次以上

Question

在对 this page 进行一些调查后，我尝试编写一个小程序将消息写入由 python 脚本开发的本地服务器。到目前为止一切顺利，问题是我只能将消息写入服务器一次。

#include <boost/array.hpp>
#include <boost/asio.hpp>

#include <iostream>
#include <string>

std::string input;
boost::asio::io_service io_service;
boost::asio::ip::tcp::resolver resolver(io_service);
boost::asio::ip::tcp::socket sock(io_service);
boost::array<char, 4096> buffer;

void connect_handler(const boost::system::error_code &ec)
{
    if(!ec){
        boost::asio::write(sock, boost::asio::buffer(input));
    }
}

void resolve_handler(const boost::system::error_code &ec, boost::asio::ip::tcp::resolver::iterator it)
{
    if (!ec){
        sock.async_connect(*it, connect_handler);
    }
}

void write_to_server(std::string const &message)
{
    boost::asio::ip::tcp::resolver::query query("127.0.0.1", "9999");
    input = message;
    resolver.async_resolve(query, resolve_handler);
    io_service.run();
}

int main()
{
    write_to_server("123");
    write_to_server("456");
}

这是python脚本

import SocketServer

class MyTCPHandler(SocketServer.BaseRequestHandler):
    """
    The RequestHandler class for our server.

    It is instantiated once per connection to the server, and must
    override the handle() method to implement communication to the
    client.
    """

    def handle(self):
        # self.request is the TCP socket connected to the client
        self.data = self.request.recv(1024).strip()
        print "{} wrote:".format(self.client_address[0])
        print self.data
        # just send back the same data, but upper-cased
        self.request.sendall(self.data.upper())     

if __name__ == "__main__":
    HOST, PORT = "localhost", 9999

    # Create the server, binding to localhost on port 9999
    server = SocketServer.TCPServer((HOST, PORT), MyTCPHandler)

    # Activate the server; this will keep running until you
    # interrupt the program with Ctrl-C
    server.serve_forever()

Answer 1

您的 io_service 在两次使用之间未被重置。

如果你想在停止后再次使用相同的 io_service，你必须调用 reset 成员函数。

write_to_server("123");
io_service.reset();
write_to_server("456");

---

也就是说，这不是设计这一切的最佳方式，您可能应该使用相同的 io_service 并且永远不要停止它，但是由于 run 成员函数io_service 将是您程序的主循环，您必须在连接回调中一个接一个地发送消息，或者创建某种事件驱动的程序来发送消息基于用户输入(例如在标准输入或套接字上读取等)。但只有在开发更大更复杂的程序时才应考虑这一点。