Re: [Bluez-devel] Nothing to read on /dev/rfcomm0

[Marcel Holtmann <marcel@holtmann.org>]

Hi Pierre-Yves,

> I'm trying to to perform an OBEX push. Using the D-Bus API, I can get
> connected to the device. /dev/rfcomm0 gets created, and I can write to
> it. But I can't read anything out of it, I always get EOF.
> 
> Here is what I do:
> 
> -Get the RFCOMM object from D-Bus
> -Call ConnectByChannel(address, channel);
> -At this point my phone prompts me and ask me if I want to accept the
> transfer or not. Of course, I accept it.
> -/dev/rfcomm0 gets created.
> -I start a stupid c program which tries to read /dev/rfcomm and shows
> what it reads on the terminal as hex (char *input[1]; fscanf(stream, "%
> c", input); printf("%x ", input[0]);
> -I write new byte[] { (byte)0x80, 0x00, 0x07, 0x10, 0x00, 0x20, 0x00};
> to /dev/rfcomm0 (that's an OBEX connect sequence as you know, this part
> is from some java code). From hcidump -X I can see it being sent to the
> device:
> 
> < ACL data: handle 42 flags 0x02 dlen 15
>     L2CAP(d): cid 0x008f len 11 [psm 3]
>       RFCOMM(d): UIH: cr 1 dlci 18 pf 0 ilen 7 fcs 0xce
>       0000: 80 00 07 10 00 20 00                              ..... .
> 
> -The device does answer:
> 
> > HCI Event: Number of Completed Packets (0x13) plen 5
>   0000: 01 2a 00 01 00                                    .*...
> > ACL data: handle 42 flags 0x02 dlen 9
>     L2CAP(d): cid 0x0040 len 5 [psm 3]
>       RFCOMM(d): UIH: cr 0 dlci 18 pf 1 ilen 0 fcs 0x8 credits 4
> > ACL data: handle 42 flags 0x02 dlen 16
>     L2CAP(d): cid 0x0040 len 12 [psm 3]
>       RFCOMM(d): UIH: cr 0 dlci 18 pf 1 ilen 7 fcs 0x8 credits 1
>       0000: a0 00 07 10 00 07 fc 
> 
> And the last line above (which is the OBEX connection acceptance
> sequence) never shows up on /dev/rfcomm0. What is wrong here?

can you reproduce it with using the rfcomm command line utility?

> Just afterwards, /dev/rfcomm0 get disconnected and the whole hcid does
> crash because of some memory error I didn't have looked at so far. Some
> info if it may help anybody:
> 
> hcid[19317]: Bluetooth HCI daemon
> hcid[19317]: Register path:/org/bluez fallback:1
> hcid[19317]: Device hci0 has been added
> hcid[19317]: Starting security manager 0
> hcid[19317]: Device hci0 has been activated
> hcid[19317]: Register path:/org/bluez/hci0 fallback:0
> hcid[19317]: Connect in progress
> hcid[19317]: rfcomm_connect_cb: connected
> hcid[19317]: Chmod return: 0
> hcid[19317]: RFCOMM node /dev/rfcomm0 was disconnected
> *** glibc detected *** corrupted double-linked list: 0x0806e8c8 ***
> Aborted
> 
> (gdb) bt
> #0  0xffffe410 in __kernel_vsyscall ()
> #1  0xb7e00101 in raise () from /lib/tls/libc.so.6
> #2  0xb7e017fd in abort () from /lib/tls/libc.so.6
> #3  0xb7e32ef7 in __fsetlocking () from /lib/tls/libc.so.6
> #4  0xb7e38c16 in malloc_usable_size () from /lib/tls/libc.so.6
> #5  0xb7e38da1 in malloc_usable_size () from /lib/tls/libc.so.6
> #6  0xb7e392df in malloc_usable_size () from /lib/tls/libc.so.6
> #7  0xb7e395d9 in free () from /lib/tls/libc.so.6
> #8  0xb7ef3f5e in hci_for_each_dev () from /usr/lib/libbluetooth.so.2
> #9  0xb7ef42d4 in hci_devid () from /usr/lib/libbluetooth.so.2
> #10 0x08053f46 in hcid_dbus_disconn_complete (local=0x0, status=0 '\0',
> handle=42, reason=22 '\026')
>     at dbus.c:1236
> #11 0x0804d1a0 in io_security_event (chan=0x806c788, cond=G_IO_IN,
> data=0x806c728) at security.c:607
> #12 0x0805feba in g_main_loop_run (loop=0x8066b08) at glib-ectomy.c:305
> #13 0x0804c7db in main (argc=0, argv=0x0) at main.c:729
> 
> (For some reason, line numbers do not show up for libluetooth.so.2 in
> the bt, even if I did add "-g" to the CFLAGS in the Makefile. Do I have
> to do something else/more to get the full information?)

Looks like a bug. That's the reason why it is still marked as
experimental.

Regards

Marcel




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