DRAFT[edit]

Open DMR Terminal Protocol is a new interface of BrandMeister DMR Server. This link provides light access for IP-based terminals. It's designed to cover many specific requirements such as:

• Good NAT traversial
• Decoded CCL-layer messages of DMR transportation
• Capabilities of push-technology (at least Google Cloud Messaging) to save battery power and traffic

This is incomplete version of specification!

The protocol is based on out Rewind Protocol and very close to our [Simple Application Protocol].

See https://github.com/BrandMeister/DigestPlay/tree/ODMRTP as a example how to connect and send audio.

Rewind Protocol[edit]

Rewind is our under-layer protocol required for communication with BrandMeister DMR Server. It is based on UDP. Byte-order is LE.

Note: protocol uses two sequence counters. One for routine messages and another one for real-time data (from REWIND_TYPE_DMR_DATA_BASE to REWIND_TYPE_DMR_AUDIO_FRAME). For real-time data you also should set flag REWIND_FLAG_REAL_TIME_1.

Protocol definition header is now available here

Messages of Protocol[edit]

Link establishment[edit]

REWIND_TYPE_KEEP_ALIVE[edit]

Keep-alive messages should be sent by client every 5 seconds. struct RewindVersionData should follow after Rewind header.

• number - DMR ID of terminal
• service - should be set to REWIND_SERVICE_OPEN_TERMINAL
• version - UTF-8 encoded message contains application name and version

Server respond to this message with the same type but without content (just header).

REWIND_TYPE_CLOSE[edit]

Simple message to close connection, has no parameters and confirmations.

REWIND_TYPE_CHALLENGE[edit]

There is no special login message, new connection should be established by REWIND_TYPE_KEEP_ALIVE. REWIND_TYPE_CHALLENGE will be send by BrandMeister Server when it detects new connection. The parameter of this message is salt value (please check example bellow).

REWIND_TYPE_AUTHENTICATION[edit]

This message is result of processing message REWIND_TYPE_CHALLENGE by client. The parameter is value of calculation SHA256 hash function (please check example bellow). A result of successful authentication procedure will be empty message REWIND_TYPE_KEEP_ALIVE.

Operational support[edit]

REWIND_TYPE_REPORT[edit]

Some kind of debugging extension. This message will be send by BrandMeister Server. Parameter of message is UTF-8 encoded text (please check example bellow).

Call control and subscription management[edit]

REWIND_TYPE_BUSY_NOTICE[edit]

Use this message to drop incoming call from the server. Message has no content.

REWIND_TYPE_SUBSCRIPTION[edit]

To simplify the process of administration and reduce amount of administrative work an application could make subscription to DMR data by itself immediately after authentication procedure. struct RewindSubscriptionData should follow after Rewind header.

• type - set to 7 for group voice call
• number - ID of talking group

On success BrandMeister Server will respond with REWIND_TYPE_SUBSCRIPTION without content.

You can make several subscriptions for connection. Subscription procedure is optional, all routing stuff can be done by LUA on the server side.

REWIND_TYPE_CANCELLING[edit]

This message cancels subscriptions created by REWIND_TYPE_SUBSCRIPTION.

This message has two options:

• To cancel all active subscriptions - the message has no content.
• To cancel particular subscription - use the same syntax as REWIND_TYPE_SUBSCRIPTION

On success BrandMeister Server will respond with REWIND_TYPE_CANCELLING without content.

Push-channel management[edit]

REWIND_TYPE_TERMINAL_IDLE[edit]

This message switches connection mode to stand-by mode if connection is already configured to support FCM push messages. After this message will send all following messages via push channel unless terminal send REWIND_TYPE_KEEP_ALIVE and authenticate. Message has no contents. BM answers with REWIND_TYPE_TERMINAL_IDLE with no contents as well.

REWIND_TYPE_TERMINAL_ATTACH[edit]

This message should be sent by application when it wants to register FCM push channel. Message should pass the data in following format:
[length of URL, WORD LE][URL of TokenService, ASCII][zerro, BYTE][length of token, WORD LE][device token, ASCII][zerro, BYTE]

Please read details about TakenService at Open DMR Terminal Protocol/Push Service

On success BrandMeister Server will respond with REWIND_TYPE_TERMINAL_ATTACH without content.

REWIND_TYPE_TERMINAL_DETACH[edit]

This message should be sent by application when it wants to de-register FCM push channel. Message has no contents. BM answers with REWIND_TYPE_TERMINAL_DETACH with no contents as well.

REWIND_TYPE_TERMINAL_WAKEUP[edit]

This message will be sent by server (mostly via push) when BrandMeister Core restarts. Application should reconnect to the server and re-subscribe all required subscriptions. Message has no contents.

Call transmission[edit]

REWIND_TYPE_DMR_DATA_BASE[edit]

This is a base number for group of messages:

• REWIND_TYPE_DMR_DATA_BASE + 1 is Voice Header (Full LC).
  This is normal structure of DMR Voice Header, 12 bytes in length (ETSI TS 102 361-1). You can skip calculation of CRC.
• REWIND_TYPE_DMR_DATA_BASE + 2 is transmission terminator. No content required or sent.

Both messages may be sent several times at once (2-3 times with same sequence number) to be sure on successful delivery.

REWIND_TYPE_DMR_AUDIO_FRAME[edit]

This message should contain triple AMBE frames of mode 33. Each of 9 bytes, 27 bytes total.

REWIND_TYPE_DMR_EMBEDDED_DATA[edit]

This message contains value of LC (10 bytes), which can be transferred via embedded signalling during voice call. Suitable to transfer Talker Alias and in-call GPS.

Additional Services[edit]

REWIND_TYPE_MESSAGE_TEXT[edit]

Message responds to message delivery (please check struct RewindTextMessageData).

• sourceID
• destinationID
• option - indicates type of message destination, private (0b00000000) or group (0b10000000)
• length - length of message in bytes
• data - message text, UTF-16LE

REWIND_TYPE_MESSAGE_STATUS[edit]

Message indicates the status of message delivery (please check struct RewindTextMessageStatus). Should be used only in case of private message!

• sourceID - should have the value of destinationID passed in RewindTextMessageData
• destinationID - should have the value of sourceID passed in RewindTextMessageData
• status - delivery status, the value of this field correspond to status octet of normal header of DMR Data Call Report (0b00001000 = success)

REWIND_TYPE_LOCATION_REPORT[edit]

This message should be sent by terminal to server and should indicate current terminal position (please check struct RewindLocationReport).

• format - should be LOCATION_FORMAT_NMEA
• length - length of NMEA string data in bytes (LE)
• data - NMEA ASCII string terminated by 0

REWIND_TYPE_LOCATION_REQUEST[edit]

This message should be sent by server to terminal to initiate one short or periodical reports (please check struct RewindLocationRequest).

• type field means type of request (LOCATION_REQUEST_SHOT, LOCATION_REQUEST_TIMED_START, LOCATION_REQUEST_TIMED_STOP)
• interval field should be used to pass report interval for LOCATION_REQUEST_TIMED_START message

Header File[edit]

#ifndef REWIND_H
#define REWIND_H

#include <stdint.h>
#include <netinet/in.h>

#ifdef __cplusplus
extern "C"
{
#endif

#pragma pack(push, 1)

#define REWIND_KEEP_ALIVE_INTERVAL   5

#define REWIND_SIGN_LENGTH           8
#define REWIND_PROTOCOL_SIGN         "REWIND01"

#define REWIND_CLASS_REWIND_CONTROL  0x0000
#define REWIND_CLASS_SYSTEM_CONSOLE  0x0100
#define REWIND_CLASS_SERVER_NOTICE   0x0200
#define REWIND_CLASS_DEVICE_DATA     0x0800
#define REWIND_CLASS_APPLICATION     0x0900
#define REWIND_CLASS_TERMINAL        0x0a00

#define REWIND_CLASS_KAIROS_DATA       (REWIND_CLASS_DEVICE_DATA + 0x00)
#define REWIND_CLASS_HYTERA_DATA       (REWIND_CLASS_DEVICE_DATA + 0x10)

#define REWIND_TYPE_KEEP_ALIVE         (REWIND_CLASS_REWIND_CONTROL + 0)
#define REWIND_TYPE_CLOSE              (REWIND_CLASS_REWIND_CONTROL + 1)
#define REWIND_TYPE_CHALLENGE          (REWIND_CLASS_REWIND_CONTROL + 2)
#define REWIND_TYPE_AUTHENTICATION     (REWIND_CLASS_REWIND_CONTROL + 3)

#define REWIND_TYPE_REDIRECTION        (REWIND_CLASS_REWIND_CONTROL + 8)

#define REWIND_TYPE_REPORT             (REWIND_CLASS_SYSTEM_CONSOLE + 0)

#define REWIND_TYPE_BUSY_NOTICE        (REWIND_CLASS_SERVER_NOTICE + 0)
#define REWIND_TYPE_ADDRESS_NOTICE     (REWIND_CLASS_SERVER_NOTICE + 1)
#define REWIND_TYPE_BINDING_NOTICE     (REWIND_CLASS_SERVER_NOTICE + 2)

#define REWIND_TYPE_EXTERNAL_SERVER    (REWIND_CLASS_KAIROS_DATA + 0)
#define REWIND_TYPE_REMOTE_CONTROL     (REWIND_CLASS_KAIROS_DATA + 1)
#define REWIND_TYPE_SNMP_TRAP          (REWIND_CLASS_KAIROS_DATA + 2)

#define REWIND_TYPE_PEER_DATA          (REWIND_CLASS_HYTERA_DATA + 0)
#define REWIND_TYPE_RDAC_DATA          (REWIND_CLASS_HYTERA_DATA + 1)
#define REWIND_TYPE_MEDIA_DATA         (REWIND_CLASS_HYTERA_DATA + 2)

#define REWIND_TYPE_CONFIGURATION      (REWIND_CLASS_APPLICATION + 0x00)
#define REWIND_TYPE_SUBSCRIPTION       (REWIND_CLASS_APPLICATION + 0x01)
#define REWIND_TYPE_CANCELLING         (REWIND_CLASS_APPLICATION + 0x02)
#define REWIND_TYPE_SESSION_POLL       (REWIND_CLASS_APPLICATION + 0x03)
#define REWIND_TYPE_DMR_DATA_BASE      (REWIND_CLASS_APPLICATION + 0x10)
#define REWIND_TYPE_DMR_AUDIO_FRAME    (REWIND_CLASS_APPLICATION + 0x20)
#define REWIND_TYPE_DMR_EMBEDDED_DATA  (REWIND_CLASS_APPLICATION + 0x27)
#define REWIND_TYPE_SUPER_HEADER       (REWIND_CLASS_APPLICATION + 0x28)
#define REWIND_TYPE_FAILURE_CODE       (REWIND_CLASS_APPLICATION + 0x29)

#define REWIND_TYPE_TERMINAL_IDLE      (REWIND_CLASS_TERMINAL + 0x00)
#define REWIND_TYPE_TERMINAL_ATTACH    (REWIND_CLASS_TERMINAL + 0x02)
#define REWIND_TYPE_TERMINAL_DETACH    (REWIND_CLASS_TERMINAL + 0x03)
#define REWIND_TYPE_TERMINAL_WAKEUP    (REWIND_CLASS_TERMINAL + 0x04)

#define REWIND_TYPE_MESSAGE_TEXT       (REWIND_CLASS_TERMINAL + 0x10)
#define REWIND_TYPE_MESSAGE_STATUS     (REWIND_CLASS_TERMINAL + 0x11)
#define REWIND_TYPE_LOCATION_REPORT    (REWIND_CLASS_TERMINAL + 0x20)
#define REWIND_TYPE_LOCATION_REQUEST   (REWIND_CLASS_TERMINAL + 0x21)

#define REWIND_FLAG_NONE             0
#define REWIND_FLAG_REAL_TIME_1      (1 << 0)
#define REWIND_FLAG_REAL_TIME_2      (1 << 1)
#define REWIND_FLAG_BUFFERING        (1 << 2)
#define REWIND_FLAG_DEFAULT_SET      REWIND_FLAG_NONE

#define REWIND_ROLE_REPEATER_AGENT   0x10
#define REWIND_ROLE_APPLICATION      0x20

#define REWIND_SERVICE_CRONOS_AGENT        (REWIND_ROLE_REPEATER_AGENT + 0)
#define REWIND_SERVICE_TELLUS_AGENT        (REWIND_ROLE_REPEATER_AGENT + 1)
#define REWIND_SERVICE_SIMPLE_APPLICATION  (REWIND_ROLE_APPLICATION    + 0)
#define REWIND_SERVICE_OPEN_TERMINAL       (REWIND_ROLE_APPLICATION    + 1)

#define REWIND_OPTION_SUPER_HEADER  (1 << 0)
#define REWIND_OPTION_LINEAR_FRAME  (1 << 1)

#define REWIND_CALL_LENGTH  10

// Keep-Alive

struct RewindVersionData
{
  uint32_t number;      // Remote ID
  uint8_t service;      // REWIND_SERVICE_*
  char description[0];  // Software name and version
};

// Redirection

union RewindAddress
{
  struct in_addr v4;
  struct in6_addr v6;
};

struct RewindRedirectionData
{
  uint16_t family;              // Address family: AF_INET, AF_INET6 or AF_UNSPEC
  uint16_t port;                // UDP port
  union RewindAddress address;  // 
};

// Generic Data Structures

struct RewindAddressData
{
  struct in_addr address;
  uint16_t port;
};

struct RewindBindingData
{
  uint16_t ports[0];
};

// Simple Application Protocol

struct RewindConfigurationData
{
  uint32_t options;  // REWIND_OPTION_*
};

struct RewindSubscriptionData
{
  uint32_t type;    // SESSION_TYPE_*
  uint32_t number;  // Destination ID
};

struct RewindSessionPollData
{
  uint32_t type;    // TREE_SESSION_*
  uint32_t flag;    // SESSION_FLAG_*
  uint32_t number;  // ID
  uint32_t state;   // 
};

struct RewindSuperHeader
{
  uint32_t type;                             // SESSION_TYPE_*
  uint32_t sourceID;                         // Source ID or 0
  uint32_t destinationID;                    // Destination ID or 0
  char sourceCall[REWIND_CALL_LENGTH];       // Source Call or zeros
  char destinationCall[REWIND_CALL_LENGTH];  // Destination Call or zeros
};

// Open DMR Terminal

struct RewindTextMessageData
{
  uint32_t reserved;       // Reserved for future use, should be 0
  uint32_t sourceID;       // Source ID
  uint32_t destinationID;  // Destination ID
  uint16_t option;         // CHEAD_GROUP_DESTINATION = 128, private message = 0
  uint16_t length;         // Length of message in bytes
  uint16_t data[0];        // Message text, UTF-16LE
};

struct RewindTextMessageStatus
{
  uint32_t reserved;       // Reserved for future use, should be 0
  uint32_t sourceID;       // Source ID
  uint32_t destinationID;  // Destination ID
  uint8_t status;          // STATUS_TYPE_*, corresponds to status field of DMR response header of data call
};

struct RewindLocationRequest
{
  uint32_t reserved;       // Reserved for future use, should be 0
  uint32_t type;           // LOCATION_REQUEST_SHOT = 0, LOCATION_REQUEST_TIMED_START = 1, LOCATION_REQUEST_TIMED_STOP = 2
  uint32_t interval;       // Interval of timed report in seconds
};

struct RewindLocationReport
{
  uint32_t reserved;       // Reserved for future use, should be 0
  uint32_t format;         // LOCATION_FORMAT_NMEA = 0
  uint16_t length;         // Length of message in bytes
  char data[0];            // NMEA position data
};

// Rewind Transport Layer

struct RewindData
{
  char sign[REWIND_SIGN_LENGTH];
  uint16_t type;    // REWIND_TYPE_*
  uint16_t flags;   // REWIND_FLAG_*
  uint32_t number;  // Packet sequence number
  uint16_t length;  // Length of following data
  uint8_t data[0];  //
};

#pragma pack(pop)

#ifdef __cplusplus
}
#endif

#endif