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 - default) | Unauthenticated | Desired
BT_SECURITY_HIGH | 3 (High) | Authenticated | Required
BT_SECURITY_FIPS (since Linux 3.15) | 4 (Secure Only) | Authenticated (P-256 based Secure Simple Pairing and Secure Authentication) | Required

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_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 the terms of the GNU Lesser General Public Licenses (LGPL).