---
name: "rfcomm"
section: "7"
platform: "linux"
package: "bluez-deprecated-tools"
version: "5.87-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/rfcomm/7"
---

# rfcomm(7)

RFCOMM protocol

## 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)](/setsockopt/2.md)** and read with **[getsockopt(2)](/getsockopt/2.md)** 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)](/socket/7.md), [rctest(1)](/rctest/1.md)

## Copyright

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