Thread: UDP talker problem executing

Hello everyone,
I am trying to program an UDP talker using sockets.
My program compiles with no problems but when I try to execute it with any volume number, I am getting always the error : sendto : message too long
and I really don't know why !!
Here is the code of my UDP talker:

Code:

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

#define BUFSIZE 100000

int main(int argc, char **argv) {
  int sfd, s, val, volume;
  struct addrinfo hints;
  struct addrinfo *result, *rp;
  struct sockaddr *sa;
  socklen_t salen;
  char buf[BUFSIZE];
  ssize_t nsend;

  if (argc != 4) {
    printf("Usage: %s service_adress server_port volume\n", argv[0]);
    exit(EXIT_FAILURE);
  }

  volume = atoi(argv[3]);
  if (volume == 0 || volume > BUFSIZE) {
    fprintf(stderr, "give a volume less then %d bytes\n", BUFSIZE);
    exit(EXIT_FAILURE);
  }

  /* buffer initializing */
  memset(buf, 'a', volume);

  memset(&hints, 0, sizeof(struct addrinfo));
  hints.ai_family = AF_UNSPEC;          /* IPv4 ou IPv6 */
  hints.ai_socktype = SOCK_DGRAM;       /* Datagram socket */
  hints.ai_flags = 0;
  hints.ai_protocol = 0;                /* Any protocol */

  s = getaddrinfo(argv[1], argv[2], &hints, &result);
  if (s != 0) {
    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
    exit(EXIT_FAILURE);
  }

  for (rp = result; rp != NULL; rp = rp->ai_next) {
    /* open socket */
    sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
    if (sfd >= 0)
      break;
  }
  if (rp == NULL) {     /* no valid adress */
    fprintf(stderr, "Unable to open a socket to %s\n", argv[1]);
    perror("socket");
    exit(EXIT_FAILURE);
  }

  /*
   * Construction of the remote address structure
   */
  sa=malloc(rp->ai_addrlen);
  memcpy(sa, rp->ai_addr, rp->ai_addrlen);
  salen=rp->ai_addrlen;

  freeaddrinfo(result); /* Not needed anymore */

  /* Allow broadcast (IPv4 only) */
  val = 1;
  if (setsockopt(sfd, SOL_SOCKET, SO_BROADCAST, &val, sizeof(val)) < 0) {
    perror("setsockopt");
    exit(EXIT_FAILURE);
  }

  /* send data */
  nsend = sendto(sfd, &buf, BUFSIZE, 0, (struct sockaddr *)&sa, salen);
  if (nsend < 0)
    perror("sendto");

  exit(EXIT_SUCCESS);
}

yes that is right thank you ! I reduced the BUFSIZE to 10.000 bytes only , it is quite enough for me.

However, I am having a new error message sendto: Address family not supported by protocol

Actually in my UDP listener, I am forcing to have an IPv6 address, does this cause the problem ?

Can anyone help me solve the error sendto: Address family not supported by protocol please ?

Originally Posted by stahta01

Code:

struct sockaddr *sa;

Code:

(struct sockaddr *)&sa

Why are you casting sa?
Why are you casting an address of a pointer?

Tim S.

That is right !! that was the origin of the error thanks !!