@Test void ipv6_notMappedIpv4() {
    String ipv6 = "::ffef:43.0.192.2";
    Endpoint endpoint = Endpoint.newBuilder().ip(ipv6).build();

    assertThat(endpoint.ipv4())
      .isNull();
    assertThat(endpoint.ipv4Bytes())
      .isNull();
    assertThat(endpoint.ipv6())
      .isNull();
    assertThat(endpoint.ipv6Bytes())
      .isNull();
  }
Many getPort operations return -1 by default. Leniently coerse to null.
zipkin/src/test/java/zipkin2/EndpointTest.java