Hi all,
I am really banging my head on a problem which sounds too easy. I have
seen that my systems (and some others as well), seem to not provide more
than 1024 bytes on a recvfrom() call. With wireshark, I see that the
system itself, at the IP layer, receives more data. I am a bit puzzled,
to phrase it lightly. I did not find any information on such a
limitation.
I have created a strip-down version of a receiver, even built it on top
of the Linux man pages samples. Out of desperation, I even set the
receivebuf size, which I think has no effect on datagram sockets.
Still... I only get 1024 bytes. Code is after my sig.
Does anybody have an idea what is going on OR a good place where to ask
this question?
Thanks,
Rainer
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/socket.h>
#include <netdb.h>
#define BUF_SIZE 2048
int
main(int argc, char *argv[])
{
struct addrinfo hints;
struct addrinfo *result, *rp;
int sfd, s;
struct sockaddr_storage peer_addr;
socklen_t peer_addr_len;
ssize_t nread;
char buf[BUF_SIZE];
if (argc != 2) {
fprintf(stderr, "Usage: %s port\n", argv[0]);
exit(EXIT_FAILURE);
}
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_family = AF_UNSPEC; /* Allow IPv4 or IPv6 */
hints.ai_socktype = SOCK_DGRAM; /* Datagram socket */
hints.ai_flags = AI_PASSIVE; /* For wildcard IP address */
hints.ai_protocol = 0; /* Any protocol */
hints.ai_canonname = NULL;
hints.ai_addr = NULL;
hints.ai_next = NULL;
s = getaddrinfo(NULL, argv[1], &hints, &result);
if (s != 0) {
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
exit(EXIT_FAILURE);
}
/* 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;
int result2;
int bufSize = 2048;
result2 = setsockopt(sfd, SOL_SOCKET, SO_RCVBUF, &bufSize,
sizeof(bufSize));
printf("result of setsockopt: %d\n", result2);
if (bind(sfd, rp->ai_addr, rp->ai_addrlen) == 0)
break; /* Success */
close(sfd);
}
if (rp == NULL) { /* No address succeeded */
fprintf(stderr, "Could not bind\n");
exit(EXIT_FAILURE);
}
freeaddrinfo(result); /* No longer needed */
/* Read datagrams and echo them back to sender */
for (;;) {
peer_addr_len = sizeof(struct sockaddr_storage);
memset(buf, 0, BUF_SIZE);
nread = recvfrom(sfd, buf, BUF_SIZE, 0,
(struct sockaddr *) &peer_addr, &peer_addr_len);
if(nread > 1024)
printf("NREAD > 1024!");
if (nread == -1)
continue; /* Ignore failed request */
char host[NI_MAXHOST], service[NI_MAXSERV];
s = getnameinfo((struct sockaddr *) &peer_addr,
peer_addr_len, host, NI_MAXHOST,
service, NI_MAXSERV, NI_NUMERICSERV);
if (s == 0)
printf("Received %ld bytes from %s:%s, msg:'%s'\n",
(long) nread, host, service, buf);
else
fprintf(stderr, "getnameinfo: %s\n",
gai_strerror(s));
}
}
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