RFCOMM(7)                 Linux System Administration                RFCOMM(7)

NAME
       rfcomm - RFCOMM protocol

SYNOPSIS

          #include <sys/socket.h>
          #include <bluetooth/bluetooth.h>
          #include <bluetooth/rfcomm.h>

          rfcomm_socket = socket(PF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);

DESCRIPTION
       The RFCOMM protocol provides emulation of serial ports over the
       L2CAP(7) protocol. The protocol is based on the ETSI standard TS 07.10.

       RFCOMM is a simple transport protocol, with additional provisions for
       emulating the 9 circuits of RS-232 (EIATIA-232-E) serial ports.

SOCKET ADDRESS

          struct sockaddr_rc {
              sa_family_t rc_family;
              unsigned short rc_bdaddr;
              unsigned char rc_channel;
          };

       Example:

          struct sockaddr_rc addr;

          memset(&addr, 0, sizeof(addr));
          addr.rc_family = AF_BLUETOOTH;
          bacpy(&addr.rc_bdaddr, bdaddr);
          addr.rc_channel = channel;

SOCKET OPTIONS
       The socket options listed below can be set by using setsockopt(2) and
       read with getsockopt(2) with the socket level set to SOL_BLUETOOTH.

   BT_SECURITY (since Linux 2.6.30)
       Channel security level, possible values:

       +-------------------+-----------------+-----------------+--------------+
       |Value              | Security Level  | Link Key Type   | Encryption   |
       +-------------------+-----------------+-----------------+--------------+
       |BT_SECURITY_SDP    | 0 (SDP Only)    | None            | Not required |
       +-------------------+-----------------+-----------------+--------------+
       |BT_SECURITY_LOW    | 1 (Low)         | Unauthenticated | Not required |
       +-------------------+-----------------+-----------------+--------------+
       |BT_SECURITY_MEDIUM | 2 (Medium -     | Unauthenticated | Desired      |
       |                   | default)        |                 |              |
       +-------------------+-----------------+-----------------+--------------+
       |BT_SECURITY_HIGH   | 3 (High)        | Authenticated   | Required     |
       +-------------------+-----------------+-----------------+--------------+
       |BT_SECURITY_FIPS   | 4 (Secure Only) | Authenticated   | Required     |
       |(since Linux 3.15) |                 | (P-256 based    |              |
       |                   |                 | Secure Simple   |              |
       |                   |                 | Pairing and     |              |
       |                   |                 | Secure          |              |
       |                   |                 | Authentication) |              |
       +-------------------+-----------------+-----------------+--------------+
       Example:

          int level = BT_SECURITY_HIGH;
          int err = setsockopt(rfcomm_socket, SOL_BLUETOOTH, BT_SECURITY, &level,
                               sizeof(level));
          if (err == -1) {
              perror("setsockopt");
              return 1;
          }

   BT_DEFER_SETUP (since Linux 2.6.30)
       Channel defer connection setup, this control if the connection
       procedure needs to be authorized by userspace before responding which
       allows authorization at profile level, possible values:

                     +------+-------------------+---------------+
                     |Value | Description       | Authorization |
                     +------+-------------------+---------------+
                     |0     | Disable (default) | Not required  |
                     +------+-------------------+---------------+
                     |1     | Enable            | Required      |
                     +------+-------------------+---------------+
       Example:

          int defer_setup = 1;
          int err = setsockopt(rfcomm_socket, SOL_BLUETOOTH, BT_DEFER_SETUP,
                               &defer_setup, sizeof(defer_setup));
          if (err == -1) {
              perror("setsockopt");
              return err;
          }

          err = listen(rfcomm_socket, 5);
          if (err) {
              perror("listen");
              return err;
          }

          struct sockaddr_rc remote_addr = {0};
          socklen_t addr_len = sizeof(remote_addr);
          int new_socket = accept(rfcomm_socket, (struct sockaddr*)&remote_addr,
                                  &addr_len);
          if (new_socket < 0) {
              perror("accept");
              return new_socket;
          }

          /* To complete the connection setup of new_socket read 1 byte */
          char c;
          struct pollfd pfd;

          memset(&pfd, 0, sizeof(pfd));
          pfd.fd = new_socket;
          pfd.events = POLLOUT;

          err = poll(&pfd, 1, 0);
          if (err) {
              perror("poll");
              return err;
          }

          if (!(pfd.revents & POLLOUT)) {
              err = read(sk, &c, 1);
              if (err < 0) {
                  perror("read");
                  return err;
              }
          }

   BT_FLUSHABLE (since Linux 2.6.39)
       Channel flushable flag, this control if the channel data can be flushed
       or not, possible values:

               +-----------------+----------------+-------------------+
               |Define           | Value          | Description       |
               +-----------------+----------------+-------------------+
               |BT_FLUSHABLE_OFF | 0x00 (default) | Do not flush data |
               +-----------------+----------------+-------------------+
               |BT_FLUSHABLE_ON  | 0x01           | Flush data        |
               +-----------------+----------------+-------------------+
   BT_POWER (since Linux 3.1)
       Channel power policy, this control if the channel shall force exit of
       sniff mode or not, possible values:

         +--------------------------+----------------+---------------------+
         |Define                    | Value          | Description         |
         +--------------------------+----------------+---------------------+
         |BT_POWER_FORCE_ACTIVE_OFF | 0x00 (default) | Don't force exit of |
         |                          |                | sniff mode          |
         +--------------------------+----------------+---------------------+
         |BT_POWER_FORCE_ACTIVE_ON  | 0x01           | Force exit of sniff |
         |                          |                | mode                |
         +--------------------------+----------------+---------------------+
   BT_CHANNEL_POLICY (since Linux 3.10)
       High-speed (AMP) channel policy, possible values:

        +----------------------------------+-------------+------------------+
        |Define                            | Value       | Description      |
        +----------------------------------+-------------+------------------+
        |BT_CHANNEL_POLICY_BREDR_ONLY      | 0 (default) | BR/EDR only      |
        +----------------------------------+-------------+------------------+
        |BT_CHANNEL_POLICY_BREDR_PREFERRED | 1           | BR/EDR Preferred |
        +----------------------------------+-------------+------------------+
        |BT_CHANNEL_POLICY_BREDR_PREFERRED | 2           | AMP Preferred    |
        +----------------------------------+-------------+------------------+
   BT_PHY (since Linux 5.10)
       Channel supported PHY(s), possible values:

                   +-------------------+-------+-----------------+
                   |Define             | Value | Description     |
                   +-------------------+-------+-----------------+
                   |BT_PHY_BR_1M_1SLOT | BIT 0 | BR 1Mbps 1SLOT  |
                   +-------------------+-------+-----------------+
                   |BT_PHY_BR_1M_3SLOT | BIT 1 | BR 1Mbps 3SLOT  |
                   +-------------------+-------+-----------------+
                   |BT_PHY_BR_1M_5SLOT | BIT 2 | BR 1Mbps 5SLOT  |
                   +-------------------+-------+-----------------+
                   |BT_PHY_BR_2M_1SLOT | BIT 3 | EDR 2Mbps 1SLOT |
                   +-------------------+-------+-----------------+
                   |BT_PHY_BR_2M_3SLOT | BIT 4 | EDR 2Mbps 3SLOT |
                   +-------------------+-------+-----------------+
                   |BT_PHY_BR_2M_5SLOT | BIT 5 | EDR 2Mbps 5SLOT |
                   +-------------------+-------+-----------------+
                   |BT_PHY_BR_3M_1SLOT | BIT 6 | EDR 3Mbps 1SLOT |
                   +-------------------+-------+-----------------+
                   |BT_PHY_BR_3M_3SLOT | BIT 7 | EDR 3Mbps 3SLOT |
                   +-------------------+-------+-----------------+
                   |BT_PHY_BR_3M_5SLOT | BIT 8 | EDR 3Mbps 5SLOT |
                   +-------------------+-------+-----------------+
RESOURCES
        <http://www.bluez.org>

REPORTING BUGS
        <linux-bluetooth@vger.kernel.org>

SEE ALSO
       socket(7), rctest(1)

COPYRIGHT
       Free use of this software is granted under ther terms of the GNU Lesser
       General Public Licenses (LGPL).

BlueZ                              May 2024                          RFCOMM(7)