java - Securing the Realm Object Server with Let’s Encrypt

Question

I do instructions of Securing the Realm Object Server with Let’s Encrypt step by step and thanks for good article of Nikola Irinchev that's work so good. When i want to use realms:// instead of realm:// and read docs of Realm Java 3.4.0 for using SSL/TLS:

SyncConfiguration syncConfiguration = new SyncConfiguration.Builder(user, "realms://host/~/myapp")
            .serverCertificate("root_ca.pem")
            .build();

that's not correct because serverCertificate() function not available and i suggest correct is:

SyncConfiguration syncConfiguration = new SyncConfiguration.Builder(user, "realms://host/~/myapp")
            .trustedRootCA("root_ca.pem")
            .build();

but after user login, realm not synced and Realm file was created in ROS can't be opened. My question is what pem file i should use in android app?

I use fullchain.pem and depart it to cert.pem and chain.pem and use all of them but my problem not resolved. Please guide me.