cdm/src/main/java/ucar/nc2/dataset/DatasetUrl.java
static private ServiceType checkIfDap4(String location) throws IOException {
    // Strip off any trailing DAP4 prefix
    if (location.endsWith(".dap"))
      location = location.substring(0, location.length() - ".dap".length());
    else if (location.endsWith(".dmr"))
      location = location.substring(0, location.length() - ".dmr".length());
    else if (location.endsWith(".dmr.xml"))
      location = location.substring(0, location.length() - ".dmr.xml".length());
    else if (location.endsWith(".dsr"))
      location = location.substring(0, location.length() - ".dsr".length());
    try (HTTPMethod method = HTTPFactory.Get(location + ".dmr.xml")) {
      int status = method.execute();
      if (status == 200) {
        Header h = method.getResponseHeader("Content-Type");
        if ((h != null) && (h.getValue() != null)) {
          String v = h.getValue();
          if (v.startsWith("application/vnd.opendap.org"))
            return ServiceType.DAP4;
        }
      }
      if (status == HttpStatus.SC_UNAUTHORIZED || status == HttpStatus.SC_FORBIDDEN)
        throw new IOException("Unauthorized to open dataset " + location);

      // not dods
      return null;
    }
  }
static private ServiceType checkIfDap4(String location) throws IOException {
    // Strip off any trailing DAP4 prefix
    if (location.endsWith(".dap"))
      location = location.substring(0, location.length() - ".dap".length());
    else if (location.endsWith(".dmr"))
      location = location.substring(0, location.length() - ".dmr".length());
    else if (location.endsWith(".dmr.xml"))
      location = location.substring(0, location.length() - ".dmr.xml".length());
    else if (location.endsWith(".dsr"))
      location = location.substring(0, location.length() - ".dsr".length());
    try (HTTPMethod method = HTTPFactory.Get(location + ".dmr.xml")) {
      int status = method.execute();
      if (status == 200) {
        Header h = method.getResponseHeader("Content-Type");
        if ((h != null) && (h.getValue() != null)) {
          String v = h.getValue();
          if (v.startsWith("application/vnd.opendap.org"))
            return ServiceType.DAP4;
        }
      }
      if (status == HttpStatus.SC_UNAUTHORIZED || status == HttpStatus.SC_FORBIDDEN)
        throw new IOException("Unauthorized to open dataset " + location);

      // not dods
      return null;
    }
  }
check for dmr