java - How to find specific devices(phone) in a network using nsd? -

i need create group of specific devices in network such in shareit app(the group share). new nsd , tried latest sample code nsdchat google. app has 4 buttons:

1. register
2. discover
3. connect
4. send

i first tap on "register" in device , tap "discover" in device b. doesn't work. after searching found 1 answer stating following change in nsdhelper

 public void initializediscoverylistener() {     mdiscoverylistener = new nsdmanager.discoverylistener() {         @override         public void ondiscoverystarted(string regtype) {             log.d(tag, "service discovery started");         }         @override         public void onservicefound(nsdserviceinfo service) {             log.d(tag, "service discovery success" + service);             if (!service.getservicetype().equals(service_type)) {                 log.d(tag, "unknown service type: " + service.getservicetype());             } else if (service.getservicename().equals(mservicename)) {                 log.d(tag, "same machine: " + mservicename);             } else if (service.getservicename().contains(mservicename)){             //here change, instead of using class variable creates              new resolvelistener.                  mnsdmanager.resolveservice(service, new nsdmanager.resolvelistener(){                      @override                     public void onresolvefailed(nsdserviceinfo serviceinfo, int errorcode) {                         log.e(tag, "resolve failed" + errorcode);                      }                      @override                     public void onserviceresolved(nsdserviceinfo serviceinfo) {                         log.e(tag, "resolve succeeded. " + serviceinfo);                         if (serviceinfo.getservicename().equals(mservicename)) {                             log.d(tag, "same ip.");                             return;                         }                         mservice = serviceinfo;                     }                 });             }         } 

following log of device (only) when tap register , device b tap discover

09-10 21:24:28.440 28618-28618/lemonlabs.test d/nsdchat: creating chat activity   09-10 21:24:28.520 28618-28620/lemonlabs.test d/dalvikvm: gc_concurrent freed 549k, 16% free 8911k/10556k, paused 5ms+7ms, total 74ms   09-10 21:24:28.530 28618-28618/lemonlabs.test d/nsdchat: starting.   09-10 21:24:28.530 28618-3757/lemonlabs.test d/chatconnection: serversocket created, awaiting connection   09-10 21:24:28.530 28618-28618/lemonlabs.test d/nsdchat: resuming.   09-10 21:24:28.540 28618-3758/lemonlabs.test d/nsdhelper: service discovery started   09-10 21:24:28.560 28618-28618/lemonlabs.test w/khrn_client: init_window num_buffers 3 min undequeued buffers 1   09-10 21:24:28.570 28618-28618/lemonlabs.test w/khrn_client: init_window window 0x508a3be8, 480x800 hinttransform 0x0 do_pre 1   09-10 21:24:50.742 28618-3758/lemonlabs.test d/nsdhelper: service registered: nsdchat   09-10 21:24:50.992 28618-3758/lemonlabs.test d/nsdhelper: service discovery successname: nsdchattype: _http._tcp.host: nullport: 0txtrecord: null   09-10 21:24:50.992 28618-3758/lemonlabs.test d/nsdhelper: same machine: nsdchat   09-10 21:24:51.002 28618-3758/lemonlabs.test d/nsdhelper: service discovery successname: nsdchattype: _http._tcp.host: nullport: 0txtrecord: null   09-10 21:24:51.002 28618-3758/lemonlabs.test d/nsdhelper: same machine: nsdchat   

following when press button:

09-10 21:26:04.464 28618-28618/lemonlabs.test d/nsdchat: pausing. 09-10 21:26:04.464 28618-3758/lemonlabs.test i/nsdhelper: discovery stopped: _http._tcp. 09-10 21:26:04.534 28618-28618/lemonlabs.test w/iinputconnectionwrapper: showstatusicon on inactive inputconnection 09-10 21:26:04.604 28618-28618/lemonlabs.test d/nsdchat: being stopped. 09-10 21:26:04.614 28618-3758/lemonlabs.test d/nsdhelper: service unregistered: nsdchat 09-10 21:26:04.614 28618-3757/lemonlabs.test e/chatconnection: error creating serversocket:                                                                 java.net.socketexception: socket closed                                                                    @ libcore.io.posix.accept(native method)                                                                    @ libcore.io.blockguardos.accept(blockguardos.java:55)                                                                    @ java.net.plainsocketimpl.accept(plainsocketimpl.java:98)                                                                    @ java.net.serversocket.implaccept(serversocket.java:202)                                                                    @ java.net.serversocket.accept(serversocket.java:127)                                                                    @ lemonlabs.test.chatconnection$chatserver$serverthread.run(chatconnection.java:113)                                                                    @ java.lang.thread.run(thread.java:856) 09-10 21:26:04.614 28618-3757/lemonlabs.test w/system.err: java.net.socketexception: socket closed 09-10 21:26:04.614 28618-3757/lemonlabs.test w/system.err:     @ libcore.io.posix.accept(native method) 09-10 21:26:04.614 28618-3757/lemonlabs.test w/system.err:     @ libcore.io.blockguardos.accept(blockguardos.java:55) 09-10 21:26:04.614 28618-3757/lemonlabs.test w/system.err:     @ java.net.plainsocketimpl.accept(plainsocketimpl.java:98) 09-10 21:26:04.614 28618-3757/lemonlabs.test w/system.err:     @ java.net.serversocket.implaccept(serversocket.java:202) 09-10 21:26:04.614 28618-3757/lemonlabs.test w/system.err:     @ java.net.serversocket.accept(serversocket.java:127) 09-10 21:26:04.614 28618-3757/lemonlabs.test w/system.err:     @ lemonlabs.test.chatconnection$chatserver$serverthread.run(chatconnection.java:113) 09-10 21:26:04.614 28618-3757/lemonlabs.test w/system.err:     @ java.lang.thread.run(thread.java:856) 09-10 21:26:04.614 28618-28618/lemonlabs.test d/nsdchat: being destroyed. 

i need device search other devices(providing service) on network , connect of them (without using ip).