// Source: http://shirleyanengineer.blogspot.com/2019/11/socket-socket-programming-in-linux-os.html
// Client side implementation of UDP client-server model

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#define PORT     8080
#define MAXLINE 1024

int main() {
    int sockfd, len, n;
    char buffer[MAXLINE];
    char *hello = "Hello from client";
    struct sockaddr_in     servaddr;
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE); }
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(PORT);
    servaddr.sin_addr.s_addr = INADDR_ANY;
    sendto(sockfd, (const char *)hello, strlen(hello), MSG_CONFIRM, 
                   (const struct sockaddr *) &servaddr, sizeof(servaddr));
    printf("Hello message sent.\n");
    n = recvfrom(sockfd, (char *)buffer, MAXLINE, MSG_WAITALL, 
                         (struct sockaddr *) &servaddr, &len);
    buffer[n] = '\0';
    printf("Server : %s\n", buffer);
    close(sockfd);
    return 0; }