It\'s not the problem to look in all domains, but I can\'t find the right way to look for any service on the network.
To my knowledge, there's not a function that will search for all available services. The reason is probably because an application publishing a service can define its own service type.
If you are only looking for services of common types (HTTP, printer, etc) you can easily create a loop to call -[instanceOfNSNetServiceBrowser searchForServicesOfType:inDomain:] with all the types you want, in all the domains you previously discovered.
The developer docs guide section on setting up a NSNetService can also be of aid.