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

int main (int argc, char *argv[]){

  int sock_cli, longitud, n;
  struct sockaddr_in dir_serv;
 
  sock_cli = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
  if (sock_cli < 0){
    printf("Error en la funcion socket() \n");
    exit(1);
  }
  bzero(&dir_serv, sizeof(dir_serv));
  dir_serv.sin_family = AF_INET;
  dir_serv.sin_port=htons(4000);
  dir_serv.sin_addr.s_addr=htonl(INADDR_ANY);
 
  longitud = sizeof (dir_serv);
 
  n = sendto(sock_cli, "prueba raw", 256, 0, (struct sockaddr *) &dir_serv, sizeof(dir_serv));
  if (n == -1){
    printf("Error en sendto() \n");
    exit(1);
  }
  printf("Valor de n: %d \n", n);
 
  close(sock_cli);

  exit(0);


}

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

int main (int argc, char *argv[]){

  int sock_serv, sock_cli, rbind, n;
  socklen_t longitud;
  struct sockaddr_in dir_serv, cliaddr;
  char buff[256];
 
  sock_serv = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
  if (sock_serv < 0){
    printf("Error en la funcion socket() \n");
    exit(1);
  }
 
  bzero(&dir_serv, sizeof(dir_serv));
  dir_serv.sin_family = AF_INET;
  dir_serv.sin_port=htons(4000);
  dir_serv.sin_addr.s_addr=htonl(INADDR_ANY);
 
  longitud = sizeof(dir_serv);
 
  rbind = bind(sock_serv, (struct sockaddr *) &dir_serv, longitud);
  if (rbind == -1){
    printf("Error en la funcion bind() \n");
    exit(1);
  }
  printf("Voy a ejecutar recvfrom() \n");
  n = recvfrom(sock_serv, buff, 256,0,(struct sockaddr *) &cliaddr, &longitud);
  if (n > 0){
    printf("He recibido algo\n");
  }
  printf("Valor de n: %d\n", n);
  close (sock_serv);

exit(1);
}