sendto() : Bad file descriptor in UDP - IPv6

Question

static void app(const char *address, int port, char *name)
{
  int sock;
  struct addrinfo server;

  sock = init_connection(address,port,&server);
  char buffer[BUF_SIZE];

  write_server(sock, &server, name); /*error is here*/

  /* ..... */   
}

The connection function

static int init_connection(const char *address, int port, struct addrinfo *server)
{
  int sockfd;

  struct addrinfo hints;

  hints.ai_family = AF_UNSPEC; /*ipv4 or ipv6 */
  hints.ai_socktype = SOCK_DGRAM; /* UDP mode */
  hints.ai_flags = 0;
  hints.ai_protocol = IPPROTO_UDP;

  char port_s[BUF_SIZE];
  sprintf(port_s,"%d",port); /* port in char* */

  if((getaddrinfo(address, port_s, &hints, &result)) != 0)
{
    perror("getaddrinfo()");
    exit(EXIT_FAILURE);
}

for (rp = result; rp != NULL; rp = rp->ai_next)
{
    //Creating the socket
    if((sockfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol)) == -1)
    {
        continue;
    }
    else
    {
        break;
    }
}

  return sockfd;
}

sendto() : The problem is in this function

static void write_server(int sockfd,struct addrinfo *client, char *buffer) /* write to server */
{
    if(sendto(sockfd, buffer, strlen(buffer), 0, client->ai_addr, sizeof (struct addrinfo)) < 0)
      {
        perror("sendto()");
        exit(EXIT_FAILURE);
      }
}

main :

int main(int argc, char **argv)
{
  if(argc != 3)
  {
    printf("Usage : %s addr_serv port_number\n", argv[0]);
    return EXIT_FAILURE;
  }

  char name[20]="name";
  int port=atoi(argv[2]); 
  app(argv[1], port, name);

  return EXIT_SUCCESS;   
}

I have a problem with the write_server function. I become sendto() : Invalid argument Does anybody have an idea of the problem ?

Thank you !

score 1 · Answer 1 · answered Apr 27 '12 at 15:28

You have not assigned a value to sockfd in init_connection. You need to call socket at least once. Check the man page of getaddrinfo for more information:

       /* getaddrinfo() returns a list of address structures.
          Try each address until we successfully bind(2).
          If socket(2) (or bind(2)) fails, we (close the socket
          and) try the next address. */

       for (rp = result; rp != NULL; rp = rp->ai_next) {
           sfd = socket(rp->ai_family, rp->ai_socktype,
                   rp->ai_protocol);
           if (sfd == -1)
               continue;

           if (bind(sfd, rp->ai_addr, rp->ai_addrlen) == 0)
               break;                  /* Success */

           close(sfd);
       }

score -1 · Answer 2 · answered Apr 27 '12 at 16:17

-1

Your sockfd is never initialised and is not valid. You are not establishing the connection anywhere. The sockfd is returned when you establish the connection.

answered Apr 27 '12 at 16:17

Drona

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sendto() : Bad file descriptor in UDP - IPv6

2 Answers2