iPhone: Bonjour NSNetService IP address and port - iphone

Question

Excuse my iPhone/Objective-C newbie status please!
I've found my HTTP server using NSNetServiceBrowser, but now I just want the IP address and port of the service found.
I've got something like the following in my delegate method:
NSNetService* server = [serverBrowser.servers objectAtIndex:0];
NSString *name = nil;
NSData *address = nil;
struct sockaddr_in *socketAddress = nil;
NSString *ipString = nil;
int port;
uint i;
for (i = 0; i < [[server addresses] count]; i++)
{
name = [server name];
address = [[server addresses] objectAtIndex:i];
socketAddress = (struct sockaddr_in *)
[address bytes];
ipString = [NSString stringWithFormat: #"%s",
inet_ntoa (socketAddress->sin_addr)];
port = socketAddress->sin_port;
NSLog(#"Server found is %s %d",ipString,port);
}
but the for loop is never entered, even though the delegate is called. Any ideas? Thanks!

Answer 1

I realize this is an old thread, but I've just run across this as well. There are a few problems with the code above:
It's not IPv6 savvy. At a
minimum, it should detect and
discard IPv6 addresses if the rest
of your app can only handle v4
addresses, but ideally you should be
prepared to pass both address
families upstream.
The port assignment will
generate incorrect values for Intel
processors. You need to use htons
to fix that.
As Andrew noted above, the
iteration should use the enhanced
for loop.
(EDIT: Added this) As noted on another related thread, the use of inet_ntoa is discouraged in favor of inet_ntop.
Putting all of this together, you get:
char addressBuffer[INET6_ADDRSTRLEN];
for (NSData *data in self.addresses)
{
memset(addressBuffer, 0, INET6_ADDRSTRLEN);
typedef union {
struct sockaddr sa;
struct sockaddr_in ipv4;
struct sockaddr_in6 ipv6;
} ip_socket_address;
ip_socket_address *socketAddress = (ip_socket_address *)[data bytes];
if (socketAddress && (socketAddress->sa.sa_family == AF_INET || socketAddress->sa.sa_family == AF_INET6))
{
const char *addressStr = inet_ntop(
socketAddress->sa.sa_family,
(socketAddress->sa.sa_family == AF_INET ? (void *)&(socketAddress->ipv4.sin_addr) : (void *)&(socketAddress->ipv6.sin6_addr)),
addressBuffer,
sizeof(addressBuffer));
int port = ntohs(socketAddress->sa.sa_family == AF_INET ? socketAddress->ipv4.sin_port : socketAddress->ipv6.sin6_port);
if (addressStr && port)
{
NSLog(#"Found service at %s:%d", addressStr, port);
}
}
}

Answer 2

The NSNetService you get back in the callback isn't ready to be used. You have to call the following method to get addresses for it:
- (void)resolveWithTimeout:(NSTimeInterval)timeout;
Implement the NSNetService delegate method to find out when it resolves:
- (void)netServiceDidResolveAddress:(NSNetService *)sender;
At that point, there should be at least one address in the service.
Also, take care to read the documentation and the header file carefully! There is some complexity to the issue here that I've glossed over.

Answer 3

Remix of the accepted answer in a category:
NSNetService+Util.h
#import <Foundation/Foundation.h>
#interface NSNetService (Util)
- (NSArray*) addressesAndPorts;
#end
#interface AddressAndPort : NSObject
#property (nonatomic, assign) int port;
#property (nonatomic, strong) NSString *address;
#end
NSNetService+Util.m
#import "NSNetService+Util.h"
#include <arpa/inet.h>
#implementation NSNetService (Util)
- (NSArray*) addressesAndPorts {
// this came from http://stackoverflow.com/a/4976808/8047
NSMutableArray *retVal = [NSMutableArray array];
char addressBuffer[INET6_ADDRSTRLEN];
for (NSData *data in self.addresses)
{
memset(addressBuffer, 0, INET6_ADDRSTRLEN);
typedef union {
struct sockaddr sa;
struct sockaddr_in ipv4;
struct sockaddr_in6 ipv6;
} ip_socket_address;
ip_socket_address *socketAddress = (ip_socket_address *)[data bytes];
if (socketAddress && (socketAddress->sa.sa_family == AF_INET || socketAddress->sa.sa_family == AF_INET6))
{
const char *addressStr = inet_ntop(
socketAddress->sa.sa_family,
(socketAddress->sa.sa_family == AF_INET ? (void *)&(socketAddress->ipv4.sin_addr) : (void *)&(socketAddress->ipv6.sin6_addr)),
addressBuffer,
sizeof(addressBuffer));
int port = ntohs(socketAddress->sa.sa_family == AF_INET ? socketAddress->ipv4.sin_port : socketAddress->ipv6.sin6_port);
if (addressStr && port)
{
AddressAndPort *aAndP = [[AddressAndPort alloc] init];
aAndP.address = [NSString stringWithCString:addressStr encoding:kCFStringEncodingUTF8];
aAndP.port = port;
[retVal addObject:aAndP];
}
}
}
return retVal;
}
#end
#implementation AddressAndPort
#end
[Yes, I have no fear of creating lots of NSObject instances...]