#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string>
#include <thread>
#include <signal.h>
#include <cstring>

#include <iostream>
#include <sstream>

const char HELLO_GROUP[] = "225.0.0.37";
const int HELLO_PORT = 12345;

static volatile bool keepRunning = true;

void usage(const char* progname)
{
    printf("Usage:\n    %s [<mcast_group> <port> [TTL]]\nNote: TTL = 0-255\n", progname);
    printf("Example:\n    %s %s %d 1\n", progname, HELLO_GROUP, HELLO_PORT);
}

void sigIntHandler(int)
{
    printf("Got SIGINT (Ctrl+C). Quitting...\n");
    keepRunning = false;
}

void sigTermHandler(int)
{
    printf("Got SIGTERM. Cleaning up. Quitting...\n");
    keepRunning = false;
}

void sigHupHandler(int)
{
    printf("Got SIGHUP. Ignoring.\n");
}

std::ostream& operator<< (std::ostream& ostr, const std::chrono::time_point<std::chrono::system_clock>& tp)
{
    std::time_t ttp = std::chrono::system_clock::to_time_t(tp);

    ostr << std::ctime(&ttp);

    return ostr;
}

int main(int argc, const char* argv[])
{
    // Handle Ctrl+C and quit gracefully
    signal(SIGINT, sigIntHandler);

    // Handle SIGTERM (15) and quit gracefully
    signal(SIGTERM, sigTermHandler);

    // Handle SIGHUP: Ignore
    signal(SIGHUP, sigHupHandler);

    if (argc != 3 && argc != 4)
    {
        usage(argv[0]);

        exit(0);
    }

    const char* mcastGroup = argv[1];
    int portNum = std::atoi(argv[2]);
    unsigned char ttl = static_cast<unsigned char>(std::atoi(argv[3]));

    struct sockaddr_in addr;
    int fd;
    //struct ip_mreq mreq;
    const char helloMsg[] = "Hello, World!";
    const char byeMsg[] = "Goodbye!";

    // Create a UDP socket
    if ((fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("socket");
        exit(1);
    }

    // Set up destination address
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = inet_addr(mcastGroup);
    addr.sin_port = htons(portNum);

    // Set up multicast TTL
    if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)) < 0)
    {
        perror("Could not set multicast TTL");
        exit(1);
    }

    // Keep sending until get a signal to terminate
    while (keepRunning)
    {
        std::ostringstream osstr;
        osstr << helloMsg << ": " << std::chrono::system_clock::now();

        if (sendto(fd, osstr.str().c_str(), osstr.str().size(), 0, (struct sockaddr*)&addr, sizeof(addr)) < 0)
        {
            perror("sendto helloMsg");
            exit(1);
        }

        std::this_thread::sleep_for(std::chrono::seconds(1));
    }

    // Say goodbye
    std::ostringstream osstr;
    osstr << byeMsg << ": " << std::chrono::system_clock::now();
    if (sendto(fd, osstr.str().c_str(), osstr.str().size(), 0, (struct sockaddr*)&addr, sizeof(addr)) < 0)
    {
        perror("sendto byeMsg");
        exit(1);
    }

    return 0;
}

In file included from t.cpp:3:
Line 19: error: stddef.h: No such file or directory
Line 17: error: thread: No such file or directory
Line 41: error: expected unqualified-id before '::' token
compilation terminated due to -Wfatal-errors.