Vincent T Vincent T - 5 months ago 21
Linux Question

BlueZ on i.MX25 : Can't connect RFCOMM socket: Operation now in progress

I'm trying to connect to a bluetooth device on embedded linux.

  • BlueZ version is 4.101.

  • Local bluetooth adapter is an USB Bluetooth dongle Trendnet TBW-107UB, for all tests.

  • I can't provide details about the target device, as it is a product of the company I work for, sorry.

Using the method described at
this page works fine on Desktop Linux Mint 17 x64, and on RiotBoard (i.MX6) Linaro Ubuntu.

However, I can't get an i.MX25 board (embedded custom Linux) to connect to the target device. Only scan works.


rfcomm0 {
# Automatically bind the device at startup
bind yes;

# Bluetooth address of the device
device 00:07:80:5A:48:93;

# RFCOMM channel for the connection
channel 1;

# Description of the connection
comment "Example Bluetooth device";

hciconfig -a output

hci0: Type: BR/EDR Bus: USB
BD Address: 00:15:83:44:39:E2 ACL MTU: 384:8 SCO MTU: 64:8
RX bytes:28633 acl:0 sco:0 events:204 errors:0
TX bytes:899 acl:0 sco:0 commands:60 errors:0
Features: 0xff 0xff 0x8f 0xfe 0x9b 0xff 0x59 0x83
Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3
Name: 'Bluetooth2.1+EDR CLASS1'
Class: 0x000000
Service Classes: Unspecified
Device Class: Miscellaneous,
HCI Version: 2.1 (0x4) Revision: 0x149c
LMP Version: 2.1 (0x4) Subversion: 0x149c
Manufacturer: Cambridge Silicon Radio (10)

rfcomm connect output

# rfcomm connect 0
Can't connect RFCOMM socket: Operation now in progress

hcitool cc output

# hcitool cc 00:07:80:5A:48:93
Can't create connection: Connection timed out

l2ping output

# l2ping 00:07:80:5A:48:93
Can't connect: Invalid exchange

While google searching, the only relevant thread I could find suggests that the rfcomm connect output could be due to a kernel 2.6.27 regression, but mine is 3.10.28 (used uname -r).

I tried with two other target bluetooth devices (of different type), the problem remains the same.

Any help is appreciated, thank you!


Rfkill block / unblock didn't seem to change anything.


It turns out the target device was requesting authentication from my i.MX25 board.
Usually, PIN code handling is done by using bluetooth-agent.
But this agent wasn't actually installed on the board (I thought it was...), so I had to manually provide the requested PIN code.

This is how I did it :

  • edit /etc/bluetooth/rfcomm.conf, like I previously did
  • "Up" the local bt adapter : hciconfig 0 up
  • Enable page & inquiry scanning : hciconfig 0 piscan (I'm not sure about this one)
  • Disable simple pairing : hciconfig 0 sspmode 0
  • Edit (or create) /usr/var/lib/bluetooth/00:15:83:44:39:E2/pincodes
  • In "pincodes" files, add line (no quotes) : "00:07:80:5A:48:93 045678"
  • Manually start bluetooth daemon : bluetoothd

00:15:83:44:39:E2 is local device bluetooth address.
00:07:80:5A:48:93 is target device bluetooth address.
045678 is target device PIN code.

l2ping works :

# l2ping 00:07:80:5A:48:93
Ping: 00:07:80:5A:48:93 from 00:15:83:44:39:E2 (data size 44) ...
4 bytes from 00:07:80:5A:48:93 id 0 time 13.14ms
4 bytes from 00:07:80:5A:48:93 id 1 time 26.34ms

rfcomm connect works :

# rfcomm connect 0
Connected /dev/rfcomm0 to 00:07:80:5A:48:93 on channel 1
Press CTRL-C for hangup

Update 06.15.2015

Today I tried l2ping on that target device again, as previously described. For some reason, it would throw me a "Permission denied" error.
This is what I figured out as a workaround :

  • Save /usr/var/lib/bluetooth/00:15:83:44:39:E2/pincodes somewhere else
  • Remove everything under /usr/var/lib/bluetooth/00:15:83:44:39:E2
  • Reboot
  • Put your saved pincodes file back under /usr/var/lib/bluetooth/00:15:83:44:39:E2
  • Retry pinging as previously described