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There are various communication modes (such as Wi-Fi and Bluetooth), and the usage of different communication modes varies greatly and often leads to problems. In addition, the convergence, sharing, and conflict of communication links cannot be handled. DSoftBus manages unified distributed communications between near-field devices and provides APIs for device discovery, connection, networking, and data transmission, regardless of the link type. It mainly provides the following capabilities:

  • Device discovery and connection in various communication modes, such as WLAN and Bluetooth
  • Unified device networking and topology management, and device information provisioning for data transmission
  • Channel setup for transmitting messages and bytes

You can use the APIs provided by DSoftBus to implement fast communications between devices without caring about the communication details, thereby deploying and running services across platforms.


Figure 1 DSoftBus architecture

Directory Structure

The main code directory structure of DSoftBus is as follows:

├── interfaces            # APIs
├── adapter               # Adapter code
├── core                  # Core code
│   ├── common            # Common code
│   ├── authentication    # Authentication code
│   ├── bus_center        # Networking code
│   ├── connection        # Connection code
│   ├── discovery         # Discovery code
│   ├── transmission      # Transmission code
│   └── frame             # Framework code
├── sdk                   # Service process code
│   ├── bus_center        # Networking code
│   ├── discovery         # Discovery code
│   ├── transmission      # Transmission code
│   └── frame             # Framework code
└── components            # Dependent component code


  • The devices between which you want to set up a connection must be in the same LAN.
  • Before setting up a connection between two devices, you must bind the devices. For details about the binding process, see relevant descriptions in the Security subsystem readme file.
  • After the data transmission is complete, the service should actively close the session and release resources.


Usage Guidelines

NOTICE: To use RPC across devices, you must have the ohos.permission.DISTRIBUTED_DATASYNC permission (which is a dangerous one).

A device can proactively discover a smartphone only when the smartphone has the Visible to all nearby devices feature enabled. (This feature is available in Settings > Super Device > Visible to > All nearby devices.)

1. Discovery

  • Publishing process
  1. Publish a service of your application.

    // Callbacks for service publishing
    typedef struct {
        void (*OnPublishSuccess)(int publishId); // Called when the service is published successfully.
        void (*OnPublishFail)(int publishId, PublishFailReason reason);// Called when the service fails to be published.
    } IPublishCallback;
    // Publish the service.
    int PublishService(const char *pkgName, const PublishInfo *info, const IPublishCallback *cb);
  2. Unpublish a service of your application.

    // Unpublish a service.
    int UnPublishService(const char *pkgName, int publishId);
  • Discovery process
  1. Discovery a specified device.

    // Callbacks for device discovery
    typedef struct {
        void (*OnDeviceFound)(const DeviceInfo *device); // Called when a device is found.
        void (*OnDiscoverFailed)(int subscribeId, DiscoveryFailReason failReason); // Called when the discovery fails to start.
        void (*OnDiscoverySuccess)(int subscribeId); // Called when the discovery starts successfully.
    } IDiscoveryCallback;
    // Start a device discovery.
    int StartDiscovery(const char *pkgName, const SubscribeInfo *info, const IDiscoveryCallback *cb);
  2. The DSoftBus notifies you of the device information via the callback once a device is found.

  3. Stop the discovery as you need.

    // Stop the discovery.
    int StopDiscovery(const char *pkgName, int subscribeId);

2. Networking

  1. Initiate a connection request with the address of the target device and the connection callback.

    // Address to connect to
    typedef struct {
        ConnectionAddrType type;
        union {
            struct BrAddr {
                char brMac[BT_MAC_LEN];
            } br;
            struct BleAddr {
                char bleMac[BT_MAC_LEN];
                uint8_t udidHash[UDID_HASH_LEN];
            } ble;
            struct IpAddr {
                char ip[IP_STR_MAX_LEN];
                uint16_t port; 
            } ip;
        } info;
        char peerUid[MAX_ACCOUNT_HASH_LEN];
    } ConnectionAddr;
    // Address types
    typedef enum {
    } ConnectionAddrType;
    // Callback for the connection result
    typedef void (*OnJoinLNNResult)(ConnectionAddr *addr, const char *networkId, int32_t retCode);
    // Initiate a connection request.
    int32_t JoinLNN(const char *pkgName, ConnectionAddr *target, OnJoinLNNResult cb);
  2. Wait for the connection result. If JoinLNN() returns success, the DSoftBus accepts the connection request and notifies you of the connection result through the callback. The addr parameter in the callback matches the target parameter in JoinLNN(). If retCode in the callback is 0, the connection is successful. In this case, the value of networkId is valid and will be used in the data transmission and disconnection APIs. If the value of retCode is not 0, the connection fails, and the value of networkId is invalid.

  3. Transmit data using transmission APIs.

  4. Initiate a disconnection request with the networkId and the callback.

    // Callback for the disconnection result
    typedef void (*OnLeaveLNNResult)(const char *networkId, int32_t retCode);
    // Initiate a disconnection request.
    int32_t LeaveLNN(const char *pkgName, const char *networkId, OnLeaveLNNResult cb);
  5. Wait until the disconnection is complete. The networkId parameter in OnLeaveLNNResult() matches networkId in LeaveLNN(). If retCode in the callback is 0, the disconnection is successful; otherwise, the disconnection fails. If the disconnection is successful, networkId becomes invalid and can no longer be used.

  6. Register and unregister callbacks for device state changes.

    // Device state events
    // Device information
    typedef struct {
        char networkId[NETWORK_ID_BUF_LEN];
        char deviceName[DEVICE_NAME_BUF_LEN];
        uint16_t deviceTypeId;
    } NodeBasicInfo;
    // Device state event callbacks
    typedef struct {
        uint32_t events; // Networking event mask
        void (*onNodeOnline)(NodeBasicInfo *info);   // Called when the device gets online.
        void (*onNodeOffline)(NodeBasicInfo *info);  // Called when the device gets offline.
        void (*onNodeBasicInfoChanged)(NodeBasicInfoType type, NodeBasicInfo *info); // Called when the device information changes.
        void (*onNodeStatusChanged)(NodeStatusType type, NodeStatus *status); // Called when the device status changed.
    } INodeStateCb;
    // Register the callback for device state events.
    int32_t RegNodeDeviceStateCb(const char *pkgName, INodeStateCb *callback);
    // Unregister the callback for device state events.
    int32_t UnregNodeDeviceStateCb(INodeStateCb *callback);

3. Transmission

  1. Create a session server with a listener. You can use the listener to monitor events such as opening and closing a session, and receiving messages or bytes.

    // Callbacks for session management
    typedef struct {
        int (*OnSessionOpened)(int sessionId, int result);
        void (*OnSessionClosed)(int sessionId);
        void (*OnBytesReceived)(int sessionId, const void *data, unsigned int dataLen);
        void (*OnMessageReceived)(int sessionId, const void *data, unsigned int dataLen);
        void (*OnStreamReceived)(int sessionId, const StreamData *data, const StreamData *ext, const StreamFrameInfo *param);
        void (*OnQosEvent)(int sessionId, int eventId, int tvCount, const QosTv *tvList);
    } ISessionListener;
    // Create a session server.
    int CreateSessionServer(const char *pkgName, const char *sessionName, const ISessionListener* listener);
  2. Open a session for sending and receiving data.

    // Open a session.
    int OpenSession(const char *mySessionName, const char *peerSessionName, const char *peerNetworkId, const char *groupId, const SessionAttribute* attr);
  3. Send data to the peer device based on the session ID.

    // Send bytes.
    int SendBytes(int sessionId, const void *data, unsigned int len);
    // Send messages.
    int SendMessage(int sessionId, const void *data, unsigned int len);
  4. Close a session with a specified ID.

    // Close a session.
    void CloseSession(int sessionId);
  5. Remove the session server.

    // Remove the session server.
    int RemoveSessionServer(const char *pkgName, const char *sessionName);

Repositories Involved

DSoftBus subsystem






DSoftBus capabilities, including discovery, networking, and transmission | 软总线发现、组网、传输功能实现 expand collapse
C and 2 more languages


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