table of contents
| 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 - 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_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¶
REPORTING BUGS¶
<linux-bluetooth@vger.kernel.org>
SEE ALSO¶
COPYRIGHT¶
Free use of this software is granted under ther terms of the GNU Lesser General Public Licenses (LGPL).
| May 2024 | BlueZ |