sendto() returning -1

gr1980 · 09-10-2010, 09:55 PM

Hello,

I am trying to write a program that sends a UDP packet over the network. When I am using the sendto function it is returning with -1 and errno "Invalid argument". I am using the cast to make sure arg 5 is being passed in as a pointer to a sockaddr struct.

I have looked at lots of examples and my code seems to follow what the examples have so I am not sure what is wring here. I am a newbie so any pointers would be great!

STATUS send_request(const packet_t * pkt)
{

int fd = -1; /* socket filedescriptor */
int result = 0; /* sendto status */
struct sockaddr_in sa; /* structure for handling internet addressing */

/* create UDP socket PF_PACKET for post 2.0 kernel */
fd = socket(PF_PACKET, SOCK_DGRAM, IPPROTO_UDP);
if (-1 == fd)
{
/* error case */
printf ("%s:%d socket failed %s", __FUNCTION__, __LINE__, strerror(errno) );
return FAILED;
}

/* setup sockaddr_in struct */
memset((char *) &sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = htons(SEND_PORT);
/* if (0 == inet_aton(SVR_IP, &sa.sin_addr))
{
// error case
printf ("%s:%d inet_aton failed", __FUNCTION__, __LINE__ );
if (-1 == (close(fd)))
{
printf ("%s:%d close failed %s", __FUNCTION__, __LINE__, strerror(errno) );
}
return FAILED;
}
*/

/* send packet */
printf ("%s:%d sendto fd:%d sizeof(packet_t):%d sizeof(pkt):%d", __FUNCTION__, __LINE__,fd, sizeof(packet_t), sizeof(pkt));

result = sendto(fd, pkt, sizeof(packet_t), 0, (struct sockaddr *)&sa, sizeof(sa));
if(-1 == result)
{
/* error case */
printf ("%s:%d sendto failed %d : %s", __FUNCTION__, __LINE__,result, strerror(errno) );
if (-1 == (close(fd)))
{
printf ("%s:%d close failed %s", __FUNCTION__, __LINE__, strerror(errno) );
}
return FAILED;
}
else if (sizeof(packet_t) == result)
{
/* success case */
printf ("%s:%d sendto successful", __FUNCTION__, __LINE__ );
if (-1 == (close(fd)))
{
printf ("%s:%d close failed %s", __FUNCTION__, __LINE__, strerror(errno) );
return FAILED;
}
}
else
{
/* catch all */
printf ("%s:%d sendto %d : %s", __FUNCTION__, __LINE__,result, strerror(errno) );
if (-1 == (close(fd)))
{
printf ("%s:%d close failed %s", __FUNCTION__, __LINE__, strerror(errno) );
}
return FAILED;
}

return SUCCESS;
}

14moose · 09-11-2010, 01:32 AM

Hi -

As far as I can tell, the only reason you'd be getting an error in "sendto()" is because you failed to assign an IP address. Here's your code, slightly reformatted, and using code blocks:

Code:

STATUS 
send_request(const char * data, int len)
{

  int fd = -1; /* socket filedescriptor */
  int result = 0; /* sendto status */
  struct sockaddr_in sa; /* structure for handling internet addressing */

  /* create UDP socket PF_PACKET for post 2.0 kernel */
  fd = socket(PF_PACKET, SOCK_DGRAM, IPPROTO_UDP);
  if (-1 == fd)
  {
    printf ("%s:%d socket failed %s", __FUNCTION__, __LINE__, strerror(errno) );
    return FAILED;
  }

  /* setup sockaddr_in struct */
  memset((char *) &sa, 0, sizeof(sa));
  sa.sin_family = AF_INET;
  sa.sin_port = htons(SEND_PORT);
  /* ??? sa.sin_addr.s_addr ??? */

  /* send packet */
  printf ("%s:%d sendto fd:%d sizeof(packet_t):%d sizeof(pkt):%d",
    __FUNCTION__, __LINE__,fd, sizeof(packet_t), sizeof(pkt));
  result = sendto(fd, data, len, 0, (struct sockaddr *)&sa, sizeof(sa));
  if(-1 == result)
  {
    ...

gr1980 · 09-11-2010, 11:13 AM

Thank you for your response. I tried adding the IP but still see the same problem. Here are the code change:

Code:

if (0 == inet_aton("255.255.255.255", &sa.sin_addr))
{
  // error case 
  printf (logbuf, sizeof(logbuf), "%s:%d inet_aton failed", __FUNCTION__, __LINE__ );
  if (-1 == (close(fd)))
  {
    printf ("%s:%d close failed %s", __FUNCTION__, __LINE__, strerror(errno) );
  }
  return FAILED;
}