ServiceDiscovery-ios

Intro

It's a simple service discovery protocol (like Zeroconf or WS-Discovery) and framework implemented in ObjectiveC. Services are available to publish their :

• int port (required)
• NSString *type (required)
• NSString *title (optional)
• NSData *payload (optional)

Usage

Publish service info

// const
#define MULTICAST_GROUP @"239.255.255.240"
#define MULTICAST_PORT 4470
#define RESPONSE_PORT (MULTICAST_PORT + 1)

#define SERVICE_TYPE @"MyServiceType1"
#define SERVICE_PORT 1204
#define SERVICE_TITLE @"Hello world"

// publish
publisher = [[ASServicePublisher alloc] initWithMulticastGroup:MULTICAST_GROUP
                                                       andPort:MULTICAST_PORT
                                                   andDelegate:self];

publisher.delegateQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
ASServiceInfo *serviceInfo = [[ASServiceInfo alloc] initWithPort:SERVICE_PORT
                                                         andType:SERVICE_TYPE
                                                        andTitle:SERVICE_TITLE
                                                      andPayload:somePayload];
[publisher registerService:serviceInfo];

Discover services

locator = [[ASServiceLocator alloc] initWithMulticastGroup:group
                                          andMulticastPort:port
                                           andResponsePort:(port + 1)
                                               andDelegate:self];
locator.mode = ASMODE_UDP;
locator.responseTimeoutMillis = 3000; // 3s
locator.delegateQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

...

- (void) didDiscoverService:(ASServiceInfo*)serviceInfo onHost:(NSString*)host {
    NSLog(@"Discovered service with title \"%@\" on %@:%i", serviceInfo.title, host, serviceInfo.port);
}

How it works

1. Publisher listens for UDP milticast requests from Locator.
2. Locator starts listening for response (UDP or TCP, depends on locator mode) and sends ServiceRequest with required fields:

• string type // service type to discover
• Mode mode // TCP or UDP response mode
• int port // either TCP or UDP port for response

3. Publisher receives request, accepts or rejects it (in listener boolean onServiceRequestReceived() or comparing requested and actual service type) and sends ServiceResponse over TCP directly to requester host and port in request (if TCP mode reponse was in request) or UDP multicast response (same UDP group but port in request).
4. Locator receives response and notifies service is found.

Testing

See Project/ for more information. Average discovery time in my home network is about 60 ms.

How to build

Just use CocoaPod:

1. clone ASServiceDiscovery-ios repo:

git clone https://github.com/4ntoine/ServiceDiscovery-ios

2. add to your project 'Podfile':

pod 'ASServiceDiscovery', :path => '(path to cloned repo 'ASServiceDiscovery.podspec' file)'

3. install pod:

pod install

Implementations

See according Java implementation: https://github.com/4ntoine/ServiceDiscovery-java

License

Free for non-commercial usage, contact for commercial usage.

Author

Anton Smirnov

dev [at] antonsmirnov [dot] name

2015