Old snippet from back in the day.

senddgram.c

//Jan 4 2009

#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

int send_datagram(char* dstaddr, int dstport, char* buffer) {

        struct hostent* peer;

        if (!(peer = gethostbyname(dstaddr))) {
                printf("Unknown host: %s\r\n", dstaddr);
                return 1;
        }

        int fd;

        if ((fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
                printf("Error creating socket.\r\n");
                return 1;
        }

        struct sockaddr_in* datagram;

        datagram->sin_family = AF_INET;
        datagram->sin_port = htons(dstport);
        memcpy(&datagram->sin_addr, peer->h_addr, peer->h_length);

        if (sendto(fd, &buffer, sizeof buffer, 0, (struct sockaddr*) &datagram, sizeof datagram) == -1) {
                printf("Error sending packet.\r\n");
                return 1;
        }
        
        close(fd);
        return 0;
}