views:

61

answers:

2

I am always getting no bytes sent, with an errno of 22 (Invalid Argument) with this code. The destination_host is set elsewhere and known to be valid, so I really don't see what is going on. MAXMSGSIZE is 1000. No errors, or warnings. I am compiling with -Wall -Werror -pedantic

char *data_rec;
u_int data_len;

int sockfd;
uint16_t *ns;
struct sockaddr_in address;
struct sockaddr *addr;

char *ip;

int i;
int errno;
int bytes_sent;

data_len = MAXMSGSIZE;
data_rec = malloc(sizeof(char)*MAXMSGSIZE);
ns = malloc(MAXMSGSIZE*sizeof(uint16_t));
ip = malloc(MAXMSGSIZE*sizeof(char));

data_rec = "some random test stuff";

sockfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(sockfd<0) {
    printf("socket() failed\n");
}

inet_ntop(AF_INET,destination_host->h_addr,ip,MAXMSGSIZE);
memset(&address, 0, sizeof(address));
address.sin_family = AF_INET;
address.sin_port = htons(theirPort);
address.sin_addr.s_addr = (unsigned long)ip;

addr = (struct sockaddr*)&address;
bind(sockfd,addr,sizeof(address));
/*Convert the message to uint16_t*/
for(i=0; i<MAXMSGSIZE; i++) {
    ns[i] = htons(data_rec[i]);
}


/* send the message */
bytes_sent = sendto(sockfd, ns, data_len, MSG_DONTWAIT, addr, sizeof(addr));
if(bytes_sent == -1) {
    printf("Error sending: %i\n",errno);
}
+5  A: 

You're giving the wrong size for the address. addr is really a struct sockaddr_in, not a struct sockaddr.

Change the last parameter of sendto to sizeof(address)

nos
Odd how this worked. An example I was following used the size of the sockaddr_in struct and worked fine.
dc
+4  A: 

inet_ntop probably isn't what you want - it converts from network (i.e. wire) format into presentation format (i.e. "1.2.3.4"). Try:

address.sin_addr.s_addr = *((unsigned long *)destination_host->h_addr);
SimonJ
In fairness, nos's answer is more likely to fix the error you're seeing, but my answer explains your next problem: why the receiver isn't seeing anything :)
SimonJ
Thanks. I would accept this answer as well if I could :P
dc