DJI Streamer

Application based on the DJI Mobile SDK for streaming synchronized video data and flight data using websockets to a custom-made server. It provides basic control functionality, such as in the DJI Go 4 / DJI Fly apps. The app should be compatible with most of the DJI drones (tested on Mavic Mini 1, Mavic Pro, Mavic 2 Dual Enterprise).

How to connect to a server and receive the data

• Implement a WebSocket server, here is our Unity example.
• In the drone GUI, click the Server IP button and fill in the IP address of the server and port (make sure that the port is open).
• The drone, as a WebSocket client, tries to establish the connection.
• If successful, the drone sends a handshake message, with the information about the drone type (ctype 0 means the client is a drone):

  {
     "type":"hello",
     "data":{
        "ctype":0,
        "drone_name":"MavicPro",
        "serial":"12345"
     }
  }

• The server needs to implement a handshake reply. The drone expects a reply message in the following format (client_id is handled by the server, can be any identification string, for instance, an ID of the websocket client):

  {
     "type":"hello_resp",
     "data":{
        "client_id":"41f28cb6",
     }
  }

• When successfully exchanged handshake messages, the drone is ready to start sending its data. To start, press the Live button.
• The drone starts sending its data in binary format, encoded as:

  | First 4 bytes == JSON bytes length | JSON bytes | 4 bytes + JSON bytes length + 4 bytes == JPEG image bytes length | JPEG bytes |
  |------------------------------------|------------|------------------------------------------------------------------|------------| 

  Binary data is split into a JSON message containing the flight data and JPEG bytes containing the current frame of the drone video feed. The first 4 bytes tell you the length of the JSON message, and the 4 bytes starting from (4 + length of JSON message) tell you the length of the JPEG image.
• When decoding the JSON bytes to a string using UTF-8, the following structure of the flight data should be received (filled with example data):

  {
     "type":"data_broadcast",
     "data":{
        "client_id":"41f28cb6",
        "altitude":234.6,
        "relative_altitude":10,
        "gps":{
           "latitude":49.24031521243185,
           "longitude":16.613207555321484
        },
        "aircraft_orientation":{
           "pitch":-4.0,
           "roll":-1.2,
           "yaw":81.2,
           "compass":81.2
        },
        "aircraft_velocity":{
           "velocity_x":0.1,
           "velocity_y":1.0,
           "velocity_z":0.1
        },
        "gimbal_orientation":{
           "pitch":0.0,
           "roll":0.0,
           "yaw":81.1,
           "yaw_relative":0.0
        },
        "satellite_count":16,
        "gps_signal_level":3,
        "battery":60,
        "sticks":{
          "left_stick": {
            "x":0
            "y":0
          }
          "right_stick": {
            "x":0
            "y":0
          }
        }
        "timestamp":"2025-06-27 14:45:06.843"
     }
  }

  Where:
  • altitude is AMSL (height above mean sea level), to work, the takeoff altitude needs to be manually set using the button Altitude.
  • relative_altitude stands for AGL (above ground level) altitude.
  • sticks report the current configuration of the physical remote controller. Values are in the range of [-660, 660]. Zero means the sticks are centered, in the default position.
• JPEG byte array can be directly decoded and displayed in the remote GUI.

How to control the drone using virtual sticks

• To create some level of autonomy, virtual sticks functionality can be used. To enable virtual stick mode, send from the server following message:

  {
     "type":"enable_control",
     "data":{
        "enable":true,
     }
  }

• The drone starts listening for command messages with the velocities of individual drone axes, in the following format:

  {
     "type":"control_command",
     "data":{
        "pitch":0,  
        "roll":0,
        "yaw":0,
        "throttle":0,
        "gimbal_pitch":0
     }
  }

  Where:
  • pitch (forward / backward), roll (left / right), throttle (up / down) are velocities in m/s. For slow speed, use values around 0.1.
  • yaw is velocity in deg/s. For slow speed, use values around 10.
  • gimbal_pitch is velocity in deg/s for tilting the gimbal up/down. For slow speed, use values around 10.