Browse LDAP servers in the domain - macos

Question

I am following this guide.
I used the following code to display LDAP servers in the domain:
#include <dns_sd.h>
#include <stdio.h>
#include <pthread.h>
void ResolveCallBack(DNSServiceRef sdRef,
DNSServiceFlags flags,
uint32_t interfaceIndex,
DNSServiceErrorType errorCode,
const char *fullname,
const char *hosttarget,
uint16_t port, /* In network byte order */
uint16_t txtLen,
const unsigned char *txtRecord,
void *context) {
}
void BrowserCallBack(DNSServiceRef inServiceRef,
DNSServiceFlags inFlags,
uint32_t inIFI,
DNSServiceErrorType inError,
const char* inName,
const char* inType,
const char* inDomain,
void* inContext) {
DNSServiceErrorType err = DNSServiceResolve(&inServiceRef,
0, // Indicate it's a shared connection.
inIFI,
inName,
inType,
inDomain,
ResolveCallBack,
NULL);
printf("DNSServiceResolve err = %x, name = %s, type=%s, domain=%s\n",
err, inName, inType, inDomain);
}
int main() {
DNSServiceRef ServiceRef;
DNSServiceErrorType err = DNSServiceBrowse(&ServiceRef, // Receives reference to Bonjour browser object.
kDNSServiceFlagsDefault, // Indicate it's a shared connection.
kDNSServiceInterfaceIndexAny, // Browse on all network interfaces.
"_ldap._tcp", // Browse for service types.
NULL, // Browse on the default domain (e.g. local.).
BrowserCallBack, // Callback function when Bonjour events occur.
NULL); // Callback context.
printf("err = 0x%x\n", err);
int sockfd = DNSServiceRefSockFD(ServiceRef);
printf("sockfd = %d\n", sockfd);
pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, 0);
pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, 0);
struct timeval timeout;
timeout.tv_sec = 1;
timeout.tv_usec = 0;
fd_set descriptors;
FD_ZERO(&descriptors);
FD_SET(sockfd, &descriptors);
int r = select(sockfd + 1, &descriptors, NULL, NULL, &timeout);
printf("r = %d\n", r);
fflush(stdout);
if (r > 0) {
if (FD_ISSET(sockfd, &descriptors)) {
// This function will call the appropiate callback to process the
// event, in this case the BrowseReply static method.
err = DNSServiceProcessResult(ServiceRef);
if (err != kDNSServiceErr_NoError) {
printf("Error on process an event in event loop, e = 0x%x\n", err);
}
}
} else if (r == -1) {
printf("The select() call failed");
}
return 0;
}
However, this didn't give me any LDAP server.
Any Help on this?
Thanks in advance
N.B:
This command returns results:
$nslookup -type=any _ldap._tcp
So there is LDAP servers in the domain.
When I tried "_http._tcp" as the registration type this returns
results.
Operating system is Mac OS X 10.9.