UDP_Multicast.cpp

This is a simple example on how to do UDP multicast.

Output if any local network is available:

Your.local.ip.addr:47776 Welcome to our multicast group!
We got another message.

#include <simple_socket/UDPSocket.h>
 
#include <array>
#include <iostream>
 
static const char multicast_group[] = "239.255.0.1";
static const unsigned short multicast_port = 47777;
static const char send_msg[] = "Welcome to our multicast group!";
static const int send_len = sizeof(send_msg) - 1;
 
int main()
{
    try {
 
    NET::UDPSocket recv_socket;
    // Allow multiple multicast receivers on this port (all get a copy)
    recv_socket.setReuseAddress(true);
    // Listen on the multicast port on any IPv4 address
    recv_socket.bind(multicast_port);
    // Join the multicast group so packets addressed to the group can be delivered to this socket
    recv_socket.joinGroup(multicast_group);
 
    NET::UDPSocket send_socket;
    // TTL 0 keeps packets self-contained on the local host
    send_socket.setMulticastTTL(0);
    // Send to group
    send_socket.sendTo(send_msg, send_len, multicast_group, multicast_port);
 
    std::array<char, 256> buffer{};
    std::string source;
    unsigned short source_port = 0;
 
    // UDP preserves datagram boundaries
    // one receiveFrom() corresponds to one datagram
    int received = recv_socket.timedReceiveFrom(buffer.data(), buffer.size(), source, source_port, 1000);
    if (received == 0)
    {
        std::cerr << "Timed out waiting for multicast datagram." << std::endl;
        return 1;
    }
 
    std::cout << "Received from " << source << ":" << source_port << ": ";
    std::cout.write(buffer.data(), received);
    std::cout << std::endl;
 
    // Not required before destruction, but shown because leaving
    // multicast groups explicitly can be useful
    recv_socket.leaveGroup(multicast_group);
 
    }
    catch (const NET::SocketException& e)
    {
        std::cerr << e.what() << std::endl;
        return 1;
    }
 
    return 0;
}