Linux over BlueZ下的C++蓝牙耳机

Posted 2023-02-19

【中文标题】Linux over BlueZ下的C++蓝牙耳机

【英文标题】：C++ Bluetooth headphones under Linux over BlueZ

【发布时间】：2018-08-02 14:07:58

【问题描述】：

我正在尝试在 Linux 下（通过 BlueZ 堆栈）为蓝牙耳机编写音频应用程序。它是嵌入式版本，所以我只想使用 C++ 和 BlueZ，没有任何 DBus 或 Python。现在我可以成功查询设备并与它们配对。但几秒钟后连接丢失。

据我了解 - 配对后应该建立一些链接以防止断开连接。但我不知道我做错了什么..

这是我的代码示例：

int main(int argc, char** argv) 

    int max_rsp, num_rsp;
    int dev_id, sock, len, flags;

    inquiry_info*   ii      = NULL;
    char        addr[19]    = 0;
    char        name[248]   = 0;
    uint8_t     cod[3]      = 0;

    const char localName[8] = "TestKIT";

    dev_id  = hci_get_route(NULL);

    sock    = hci_open_dev(dev_id);
    if (dev_id < 0 || sock < 0) 

        std::cerr << "HCI open device:\t\t" << strerror(errno) << std::endl;
        return -1;

    
    hci_write_local_name(sock, localName, 8);

    std::cout << std::endl;
    std::cout << "Device name set to:\t\"" << localName << "\"" << std::endl;

    len = 8;
    max_rsp = 255;
    flags   = IREQ_CACHE_FLUSH;
    ii  = new inquiry_info[max_rsp * sizeof(inquiry_info)];

    num_rsp = hci_inquiry(dev_id, len, max_rsp, NULL, &ii, flags);
    if (num_rsp < 0) 

        std::cerr << "HCI inquiry: " << strerror(errno) << std::endl;

    

    std::cout << std::endl;
    std::cout << "=========================================================================" << std::endl;
    std::cout << " #\t" << "BTA\t\t\t" << "Name\t\t\t\t" << "COD" << std::endl;
    std::cout << "-------------------------------------------------------------------------" << std::endl;

        for (int i = 0; i < num_rsp; ++i) 

        ba2str(&ii[i].bdaddr, addr);
        memset(name, 0, sizeof(name));

        if (hci_read_remote_name(sock, &ii[i].bdaddr, sizeof(name), name, 0) < 0) 

            strcpy(name, "[unknown]");

        

        hci_read_class_of_dev(sock, cod, 0);

        std::cout << std::setw(2) << std::setfill(' ') << i + 1 << '.' << "\t";
        std::cout << addr << "\t";
        std::cout << std::setw(30) << std::left << name << "\t" << std::right;
        std::cout << "0x";
        std::cout << std::setw(2) << std::setfill('0') << std::hex << static_cast<unsigned int>(cod[2]);
        std::cout << std::setw(2) << std::setfill('0') << std::hex << static_cast<unsigned int>(cod[1]);
        std::cout << std::setw(2) << std::setfill('0') << std::hex << static_cast<unsigned int>(cod[0]);
        std::cout << std::endl;

    

    std::cout << "=========================================================================" << std::endl;

    unsigned int userChoise = 0;

    std::cout << std::endl;
    std::cout << "Device to connect: ";

    std::cin >> userChoise;

    uint16_t    handle;
    unsigned int    ptype   = HCI_DM1 | HCI_DM3 | HCI_DM5 | HCI_DH1 | HCI_DH3 | HCI_DH5;

    if (userChoise > 0 && userChoise <= num_rsp) 

        std::cout << "Connecting to device #" << userChoise << " ..." << std::endl;
        std::cout << std::endl;

        if (hci_create_connection(sock, &ii[userChoise - 1].bdaddr, htobs(ptype), 0, 0, &handle, 0) < 0) 

            std::cerr << "HCI create connection:\t" << strerror(errno) << std::endl;

         else 

            std::cout << "Connection:\t\tOK" << std::endl;

        

        if (hci_authenticate_link(sock, handle, 0) < 0) 

            std::cerr << "HCI authenticate connection:\t" << strerror(errno) << std::endl;

         else 

            std::cout << "Authentication:\t\tOK" << std::endl;

        

        if (hci_encrypt_link(sock, handle, 1, 0) < 0) 

            std::cerr << "HCI encrypt connection:\t" << strerror(errno) << std::endl;

         else 

            std::cout << "Encryption:\t\tOK" << std::endl;

        

     else 

        std::cout << "Wrong device number: " <<  userChoise << " (should be ";

        if (num_rsp > 1) 

            std::cout << "in range [1 .. " << num_rsp << "]";

         else 

            std::cout << "1";

        

        std::cout << ")" << std::endl;

    

    hci_close_dev(sock);

    close(sock);

    // Connection to prevent disconnect
    struct sockaddr_l2 rAddr;
    int sk = socket(PF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP);

    if (sk < 0) 

        std::cerr << "Socket:\t" << strerror(errno) << std::endl;

    

    memset(&rAddr, 0, sizeof(rAddr));
    rAddr.l2_family = AF_BLUETOOTH;
    rAddr.l2_psm = 0x1001;
    rAddr.l2_bdaddr = ii[userChoise - 1].bdaddr;

    if (connect(sk, (struct sockaddr *) &rAddr, sizeof(rAddr)) < 0 ) 

        std::cerr << "Connect:\t" << strerror(errno) << std::endl;

     

    std::cout << "Socket "sk": " << sk << std::endl;

    delete [] ii;
    ii = NULL;

    return 0;

【参考方案1】：

好的，找到了解决方案——它是在连接之前初始化所有 SDP 例程以获取所需协议的所需通道。 目前 RFCOMM 连接建立成功。

这是它目前的工作方式：C++ example form my GitHub。

附：注意 - 这个项目现在没有维护，因为我没有足够的时间。但未来可能会改变