question: protected void awaitAccept ( ) throws IOException { final Selector serverSelector = Selector . open ( ) ; try { final SelectionKey serverKey = server . register ( serverSelector , SelectionKey . OP_ACCEPT ) ; try { serverSelector . select ( ) ; final Set < SelectionKey > keys = serverSelector . selectedKeys ( ) ; final Iterator < SelectionKey > iter = keys . iterator ( ) ; while ( iter . hasNext ( ) ) { final SelectionKey key = ( SelectionKey ) iter . next ( ) ; iter . remove ( ) ; if ( key != serverKey ) throw new AssertionError ( ) ; break ; } } finally { serverKey . cancel ( ) ; } } finally { serverSelector . close ( ) ; } }
target:  Blocking wait for a client connection.