@Nullable
    public InetSocketAddress getPeer() {
        return nextPeer();
    }
@Test
    public void getPeer_all() throws Exception{
        SeedPeers seedPeers = new SeedPeers(MAINNET);
        for (int i = 0; i < MAINNET.getAddrSeeds().length; ++i) {
            assertThat("Failed on index: "+i, seedPeers.getPeer(), notNullValue());
        }
        assertThat(seedPeers.getPeer(), equalTo(null));
    }