说明

直接使用asio库来发送，这样比较简单

show me the code

#pragma once
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>

// 3rd party includes.
#include <asio.hpp>
#include <string>

using asio::ip::udp;


class c_multisock
{
public:
	c_multisock():v_socket(v_service)
	{}
	void read()
	{
		asio::ip::udp::endpoint sender;
		std::vector<char> buffer;
		std::size_t bytes_readable = 0;

		asio::socket_base::bytes_readable num_of_bytes_readable(true);
		v_socket.io_control(num_of_bytes_readable);
		// Get the value from the command.
		bytes_readable = num_of_bytes_readable.get();
		// If there is no data available, then sleep.
		if (!bytes_readable)
		{
			return;
		}
		// Resize the buffer to store all available data.
		buffer.resize(bytes_readable);
		// Read available data.
		v_socket.receive_from(
			asio::buffer(buffer, bytes_readable),
			sender);

		// Extract data from the buffer.
		std::string message(buffer.begin(), buffer.end());

		// Output data.
		std::cout << "Received message: ";
		std::cout << message << std::endl;
	}






	void write(uint8_t *data, size_t len)
	{
		//char buffer[256];
		//sprintf(buffer, msearchmsgfmt, "upnp:rootdevice");
		/*socket.async_send_to(
			boost::asio::buffer(buffer, strlen(buffer)), endpoint_,
			boost::bind(handle_send_to, this,
				boost::asio::placeholders::error));*/

		v_socket.send_to(asio::buffer(data, len), v_destination);
	}
	int asio_init(const char * ip,uint16_t port, bool receiver)
	{
		asio::ip::address address =
			asio::ip::address::from_string(ip); //"239.255.255.250"
	
		//udp::socket socket(v_service);
		v_socket.open(asio::ip::udp::v4());

		// Allow other processes to reuse the address, permitting other processes on
		// the same machine to use the multicast address.
		v_socket.set_option(udp::socket::reuse_address(true));

		// Guarantee the loopback is enabled so that multiple processes on the same
		// machine can receive data that originates from the same socket.
		v_socket.set_option(asio::ip::multicast::enable_loopback(true));
		v_receiver = receiver;
		v_socket.bind(
			udp::endpoint(asio::ip::address_v4::any(),
				receiver ? port /* same as multicast port */
				: 16200/* any */));
		v_destination = udp::endpoint(address, port);

		// Join group.
		v_socket.set_option(asio::ip::multicast::join_group(address));

		// Start read or write loops based on command line options.
		//if (receiver) read(socket);
		//else          write(socket, destination);
		return 0;
	}
private:
	bool v_receiver;
	udp::endpoint v_destination;
	asio::io_context v_service;
	udp::socket v_socket;
};