public boolean isVm0Primary() throws Exception {
    int port = client1.invoke(InterestListEndpointDUnitTest::getPrimaryPort);
    return port == PORT1;
  }
put on non interest list ep and verify updates
geode-core/src/distributedTest/java/org/apache/geode/internal/cache/tier/sockets/InterestListEndpointDUnitTest.java