public String getUniqueId() {
    StringBuilder sb = new StringBuilder();
    addFixedToString(sb, false);

    // add version if not current
    short version = memberData.getVersionOrdinal();
    if (version != KnownVersion.CURRENT.ordinal()) {
      sb.append("(version:").append(Versioning.getVersion(version)).append(')');
    }

    return sb.toString();
  }
Set the membership port. This is done in loner systems using client/server connection
information to help form a unique ID
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/MemberIdentifierImpl.java