Q: I want to use Bonjour to advertise my services but I only want to do so on a specific set of networking interfaces. Is this possible?A: Yes. However, you will NOT be able to use the NSNetServices and CFNetServices APIs to do this. You will need to use the DNSServiceDiscovery socket-based API. You can register your service by issuing a call to DNSServiceRegister(), paying close attention to the third parameter specifying an interface index. Determining which interface index maps to a specific interface name can be done by calling if_nametoindex(). See below for an example: Listing 1: Example function that registers a service on a single interface.
static int doBonjourRegisterOnSingleInterface(
char * interface_name, // e.g., "en0", "en1", etc.
DNSServiceRef * ssr,
DNSServiceRegisterReply callBack
)
{
int err = 0;
DNSServiceFlags flags = kDNSServiceFlagsDefault;
uint32_t int_index = 0;
const char *name = "Clarus";
const char *regtype = "_http._tcp";
const char *domain = NULL; // default domain
const char *host = NULL; // default host
uint16_t port = 9999;
uint16_t txtLen = 5;
const char txtRecord[] = "\x04Moof";
// Resolve the index of the specified interface.
int_index = if_nametoindex(interface_name);
if(int_index != 0) {
err = DNSServiceRegister(
ssr,
flags,
int_index,
name, /* may be NULL */
regType,
domain, /* may be NULL */
host, /* may be NULL */
htons(port),
txtLen,
txtRecord,
callback, /* may be NULL */
NULL /* may be NULL */
);
} else {
// Desired interface name could not be resolved.
err = -1;
}
return err;
}
Note: Be mindful of the formats and types for the data parameters passed into DNSServiceRegister(), e.g., "the TXT record string must be in DNS TXT record format of [length byte] [data] [length byte] [data] ...", otherwise you will receive an invalid parameter (-65540) error. See Q&A 1306. Document Revision History| Date | Notes |
|---|
| 2007-02-12 | First Version |
Posted: 2007-02-12
|
