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.TH "RFCOMM" "7" "May 2024" "BlueZ" "Linux System Administration"
.SH NAME
rfcomm \- RFCOMM protocol
.SH SYNOPSIS
.INDENT 0.0
.INDENT 3.5
.sp
.EX
#include <sys/socket.h>
#include <bluetooth/bluetooth.h>
#include <bluetooth/rfcomm.h>

rfcomm_socket = socket(PF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);
.EE
.UNINDENT
.UNINDENT
.SH DESCRIPTION
.sp
The RFCOMM protocol provides emulation of serial ports over the L2CAP(7)
protocol. The protocol is based on the ETSI standard TS 07.10.
.sp
RFCOMM is a simple transport protocol, with additional provisions for emulating
the 9 circuits of RS\-232 (EIATIA\-232\-E) serial ports.
.SH SOCKET ADDRESS
.INDENT 0.0
.INDENT 3.5
.sp
.EX
struct sockaddr_rc {
    sa_family_t rc_family;
    unsigned short rc_bdaddr;
    unsigned char rc_channel;
};
.EE
.UNINDENT
.UNINDENT
.sp
Example:
.INDENT 0.0
.INDENT 3.5
.sp
.EX
struct sockaddr_rc addr;

memset(&addr, 0, sizeof(addr));
addr.rc_family = AF_BLUETOOTH;
bacpy(&addr.rc_bdaddr, bdaddr);
addr.rc_channel = channel;
.EE
.UNINDENT
.UNINDENT
.SH SOCKET OPTIONS
.sp
The socket options listed below can be set by using \fBsetsockopt(2)\fP and read
with \fBgetsockopt(2)\fP with the socket level set to SOL_BLUETOOTH.
.SS BT_SECURITY (since Linux 2.6.30)
.sp
Channel security level, possible values:
.TS
box center;
l|l|l|l.
T{
Value
T}	T{
Security Level
T}	T{
Link Key Type
T}	T{
Encryption
T}
_
T{
\fBBT_SECURITY_SDP\fP
T}	T{
0 (SDP Only)
T}	T{
None
T}	T{
Not required
T}
_
T{
\fBBT_SECURITY_LOW\fP
T}	T{
1 (Low)
T}	T{
Unauthenticated
T}	T{
Not required
T}
_
T{
\fBBT_SECURITY_MEDIUM\fP
T}	T{
2 (Medium \- default)
T}	T{
Unauthenticated
T}	T{
Desired
T}
_
T{
\fBBT_SECURITY_HIGH\fP
T}	T{
3 (High)
T}	T{
Authenticated
T}	T{
Required
T}
_
T{
\fBBT_SECURITY_FIPS\fP (since Linux 3.15)
T}	T{
4 (Secure Only)
T}	T{
Authenticated (P\-256 based Secure Simple Pairing and Secure Authentication)
T}	T{
Required
T}
.TE
.sp
Example:
.INDENT 0.0
.INDENT 3.5
.sp
.EX
int level = BT_SECURITY_HIGH;
int err = setsockopt(rfcomm_socket, SOL_BLUETOOTH, BT_SECURITY, &level,
                     sizeof(level));
if (err == \-1) {
    perror(\(dqsetsockopt\(dq);
    return 1;
}
.EE
.UNINDENT
.UNINDENT
.SS BT_DEFER_SETUP (since Linux 2.6.30)
.sp
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:
.TS
box center;
l|l|l.
T{
Value
T}	T{
Description
T}	T{
Authorization
T}
_
T{
\fB0\fP
T}	T{
Disable (default)
T}	T{
Not required
T}
_
T{
\fB1\fP
T}	T{
Enable
T}	T{
Required
T}
.TE
.sp
Example:
.INDENT 0.0
.INDENT 3.5
.sp
.EX
int defer_setup = 1;
int err = setsockopt(rfcomm_socket, SOL_BLUETOOTH, BT_DEFER_SETUP,
                     &defer_setup, sizeof(defer_setup));
if (err == \-1) {
    perror(\(dqsetsockopt\(dq);
    return err;
}

err = listen(rfcomm_socket, 5);
if (err) {
    perror(\(dqlisten\(dq);
    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(\(dqaccept\(dq);
    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(\(dqpoll\(dq);
    return err;
}

if (!(pfd.revents & POLLOUT)) {
    err = read(sk, &c, 1);
    if (err < 0) {
        perror(\(dqread\(dq);
        return err;
    }
}
.EE
.UNINDENT
.UNINDENT
.SS BT_FLUSHABLE (since Linux 2.6.39)
.sp
Channel flushable flag, this control if the channel data can be flushed or
not, possible values:
.TS
box center;
l|l|l.
T{
Define
T}	T{
Value
T}	T{
Description
T}
_
T{
\fBBT_FLUSHABLE_OFF\fP
T}	T{
0x00 (default)
T}	T{
Do not flush data
T}
_
T{
\fBBT_FLUSHABLE_ON\fP
T}	T{
0x01
T}	T{
Flush data
T}
.TE
.SS BT_CHANNEL_POLICY (since Linux 3.10)
.sp
High\-speed (AMP) channel policy, possible values:
.TS
box center;
l|l|l.
T{
Define
T}	T{
Value
T}	T{
Description
T}
_
T{
\fBBT_CHANNEL_POLICY_BREDR_ONLY\fP
T}	T{
0 (default)
T}	T{
BR/EDR only
T}
_
T{
\fBBT_CHANNEL_POLICY_BREDR_PREFERRED\fP
T}	T{
1
T}	T{
BR/EDR Preferred
T}
_
T{
\fBBT_CHANNEL_POLICY_BREDR_PREFERRED\fP
T}	T{
2
T}	T{
AMP Preferred
T}
.TE
.SS BT_PHY (since Linux 5.10)
.sp
Channel supported PHY(s), possible values:
.TS
box center;
l|l|l.
T{
Define
T}	T{
Value
T}	T{
Description
T}
_
T{
\fBBT_PHY_BR_1M_1SLOT\fP
T}	T{
BIT 0
T}	T{
BR 1Mbps 1SLOT
T}
_
T{
\fBBT_PHY_BR_1M_3SLOT\fP
T}	T{
BIT 1
T}	T{
BR 1Mbps 3SLOT
T}
_
T{
\fBBT_PHY_BR_1M_5SLOT\fP
T}	T{
BIT 2
T}	T{
BR 1Mbps 5SLOT
T}
_
T{
\fBBT_PHY_BR_2M_1SLOT\fP
T}	T{
BIT 3
T}	T{
EDR 2Mbps 1SLOT
T}
_
T{
\fBBT_PHY_BR_2M_3SLOT\fP
T}	T{
BIT 4
T}	T{
EDR 2Mbps 3SLOT
T}
_
T{
\fBBT_PHY_BR_2M_5SLOT\fP
T}	T{
BIT 5
T}	T{
EDR 2Mbps 5SLOT
T}
_
T{
\fBBT_PHY_BR_3M_1SLOT\fP
T}	T{
BIT 6
T}	T{
EDR 3Mbps 1SLOT
T}
_
T{
\fBBT_PHY_BR_3M_3SLOT\fP
T}	T{
BIT 7
T}	T{
EDR 3Mbps 3SLOT
T}
_
T{
\fBBT_PHY_BR_3M_5SLOT\fP
T}	T{
BIT 8
T}	T{
EDR 3Mbps 5SLOT
T}
.TE
.SH RESOURCES
.sp
 <http://www.bluez.org> 
.SH REPORTING BUGS
.sp
 <linux\-bluetooth@vger.kernel.org> 
.SH SEE ALSO
.sp
socket(7), rctest(1)
.SH COPYRIGHT
Free use of this software is granted under the terms of the GNU
Lesser General Public Licenses (LGPL).
.\" Generated by docutils manpage writer.
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