Brad,
I tried the L2CAP as the transport and now I can have multiple client
connected at the same time. Thanks !
Han
On Wed, Mar 2, 2011 at 8:45 PM, Han <keepsimple@xxxxxxxxx> wrote:
> On Wed, Mar 2, 2011 at 6:31 PM, Brad Midgley <bmidgley@xxxxxxxxx> wrote:
>> Han
>>
>>> I have a client / server application running over bluetooth using
>>> RFCOMM as transport. I am using socket API in C with AF_BLUETOOTH,
>>> SOCK_STREAM and BTPROTO_RFCOMM.
>>
>> rfcomm is the wrong protocol if you want to have multiple connections
>> to one server.
>
> Thanks Brad. What should be the right protocol to use?
>
>>
>> In case you have no choice, I've appended a very old howto suggesting
>> a way to multiplex rfcomm for gps, but it's generally unreliable
>> because clients cache sdp records unpredictably.
>
> thanks for the detailed info. It seems that rfcomm.conf has to
> include one entry for each connection with different channel? In my
> case, I really don't know how many (parallel) client connections in
> advance. It's all dynamic.
>
> Han
>
>>
>> ================================
>>
>> Bluetooth & GPS
>> I would like to have a multifunction GPS unit... logging, repeating
>> gps location data over bluetooth for two clients. gpsd is running and
>> receiving from the local gps.
>>
>> Next, to make it repeat the gps stream, I started by installing gpspipe.
>>
>> start with two rfcomm listeners in /etc/bluetooth/rfcomm.conf:
>>
>> #
>> # cat /etc/bluetooth/rfcomm.conf
>> #
>> # RFCOMM configuration file.
>> #
>>
>> rfcomm0 {
>> listen yes;
>>
>> # Bluetooth address of the device
>> device hci0;
>>
>> # RFCOMM channel for the connection
>> channel 1;
>>
>> # Description of the connection
>> comment "gps repeater channel 1";
>> }
>>
>> rfcomm1 {
>> listen yes;
>>
>> # Bluetooth address of the device
>> device hci0;
>>
>> # RFCOMM channel for the connection
>> channel 2;
>>
>> # Description of the connection
>> comment "gps repeater channel 2";
>> }
>>
>> next, in /etc/bluetooth/rfcomm/rfcomm-gps-repeater:
>>
>> #!/bin/sh
>> # use: rfcomm-gps-repeater rfcommx next-port-number
>> # eg: rfcomm-gps-repeater rfcomm0 2 & rfcomm-gps-repeater rfcomm1 1 &
>> while true;
>> do
>> rfcomm show | grep $1 > /dev/null 2> /dev/null
>> if [ "$?" != "1" ] ; then
>> /usr/bin/sdptool add --channel=$2 SP
>> /usr/bin/gpspipe -r >/dev/$1;
>> fi
>> sleep 1;
>> done
>>
>> I run two of these in parallel, pointing each one to the *next* rfcomm
>> channel it should advertise via sdp. This is so the next bluetooth
>> client to scan sdp will find the available repeater.
>>
>> It seems the rfcomm listener is not prepared to serve two ports. The
>> new /etc/bluetooth/rfcomm/rfcomm-listen:
>>
>> #!/bin/sh
>> while $1 -r -f $2 listen $3;do continue;done
>>
>> Finally, execute everything properly in /etc/init.d/S30bluetooth:
>>
>> ...
>> RFCOMM_GPS_REPEATER=/etc/bluetooth/rfcomm/rfcomm-gps-repeater
>> ...
>> #$RFCOMM_LISTEN $RFCOMM_EXEC $RFCOMM_CONFIG > /dev/null 2>&1 &
>> $RFCOMM_LISTEN $RFCOMM_EXEC $RFCOMM_CONFIG rfcomm0 > /dev/null 2>&1 &
>> $RFCOMM_LISTEN $RFCOMM_EXEC $RFCOMM_CONFIG rfcomm1 >
>> /dev/null 2>&1 &
>> #$RFCOMM_GETTY > /dev/null 2>&1 &
>> $RFCOMM_GPS_REPEATER rfcomm0 2 > /dev/null 2>&1 &
>> $RFCOMM_GPS_REPEATER rfcomm1 1 > /dev/null 2>&1 &
>> ...
>>
>> You may have to change hcid.conf to contain "lm accept,master" so the
>> board insists on being the bluetooth master device. I was getting i/o
>> errors before I did that.
>>
>> --
>> Brad Midgley
>>
>
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