Fatal error on running finishFromCode in Java 3.0.6

Trying to run method finishOAuth of DropboxConnector class (startOAuth has no problems when running. 

public DropboxConnector() {
    DbxAppInfo appInfo = new DbxAppInfo(DropboxHelper.APP_KEY, DropboxHelper.APP_SECRET);
    this.config = new DbxRequestConfig("text-edit/0.1");
    this.webAuth = new DbxWebAuth(config, appInfo);
}

public String startOAuth(){
    DbxWebAuth.Request authRequest = DbxWebAuth.newRequestBuilder().build();
    return webAuth.authorize(authRequest);
}

public String finishOAuth(String code) throws DbxException {
    DbxAuthFinish authFinish = webAuth.finishFromCode(code);
    return authFinish.getAccessToken();
}

getting Fatal Error on calling finishFromCode(code). Debug shows code is the same I get from dropbox auth page.

Here is the stack:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.andrew.mywardrobe, PID: 7916
android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1303)
at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:86)
at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:74)
at java.net.InetAddress.getAllByName(InetAddress.java:752)
at com.android.okhttp.internal.Network$1.resolveInetAddresses(Network.java:29)
at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:187)
at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:156)
at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:98)
at com.android.okhttp.internal.http.HttpEngine.createNextConnection(HttpEngine.java:345)
at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:328)
at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:246)
at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:457)
at com.android.okhttp.internal.huc.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:126)
at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getOutputStream(HttpURLConnectionImpl.java:257)
at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.getOutputStream(DelegatingHttpsURLConnection.java:218)
at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.getOutputStream(HttpsURLConnectionImpl.java)
at com.dropbox.core.http.StandardHttpRequestor.getOutputStream(StandardHttpRequestor.java:123)
at com.dropbox.core.http.StandardHttpRequestor.access$000(StandardHttpRequestor.java:28)
at com.dropbox.core.http.StandardHttpRequestor$Uploader.<init>(StandardHttpRequestor.java:133)
at com.dropbox.core.http.StandardHttpRequestor.startPost(StandardHttpRequestor.java:72)
at com.dropbox.core.http.StandardHttpRequestor.startPost(StandardHttpRequestor.java:28)
at com.dropbox.core.DbxRequestUtil.startPostRaw(DbxRequestUtil.java:237)
at com.dropbox.core.DbxRequestUtil.startPostNoAuth(DbxRequestUtil.java:216)
at com.dropbox.core.DbxRequestUtil$2.run(DbxRequestUtil.java:453)
at com.dropbox.core.DbxRequestUtil.runAndRetry(DbxRequestUtil.java:498)
at com.dropbox.core.DbxRequestUtil.doPostNoAuth(DbxRequestUtil.java:450)
at com.dropbox.core.DbxWebAuth.finish(DbxWebAuth.java:401)
at com.dropbox.core.DbxWebAuth.finish(DbxWebAuth.java:383)
at com.dropbox.core.DbxWebAuth.finishFromCode(DbxWebAuth.java:295)
at com.example.andrew.mywardrobe.dropbox.DropboxConnector.finishOAuth(DropboxConnector.java:39)
 

dropbox-core-sdk-3.0.6.jar is added to dependencies.