- serial, reliable, connection-oriented transport protocol on top of
  Bluetooth, IrDA, (?)

- defines concept of "channels" similar to ports in TCP


Implementation (on Linux):

- Kernel module

- new endpoint type sockaddr_rc (compatible to sockaddr)

- can be used with the usual BSD socket API (bind(2), accept(2),
  connect(2) etc.)

- definition:

  (from bluetooth/rfcomm.h)

  struct sockaddr_rc {
      sa_family_t     rc_family;   //AF_BLUETOOTH|AF_...
      bdaddr_t        rc_bdaddr;
      uint8_t         rc_channel;
  }

  /* BD Address */ (from bluetooth/bluetooth.h)
  typedef struct {
        uint8_t b[6];
  } __attribute__((packed)) bdaddr_t;

  //this is confusing -- it appears the rfcomm socket type
  //(sockaddr_rc) refers to a bluetooth-specific endpoint (rc_bdaddr)
  //explicitly

char *batostr(const bdaddr_t *ba)
{
        char *str = malloc(18);
        if (!str)
                return NULL;

        sprintf(str, "%2.2X:%2.2X:%2.2X:%2.2X:%2.2X:%2.2X",
                ba->b[0], ba->b[1], ba->b[2], 
                ba->b[3], ba->b[4], ba->b[5]);
        return str;
}

bluetooth/rfcomm.h basically defines only the sockaddr_rc
structure. The hard work happens in the kernel.



basic usage (Bluetooth transport)
---------------------------------

connecting:

input:
bdaddr_t *src, bdaddr_t *dst, uint8_t channel;


work:

        sockaddr_rc self, peer;

        self.rc_family = AF_BLUETOOTH;
        bacpy(&self.rc_bdaddr, src);
        self.rc_channel = 0;

        peer.rc_family = AF_BLUETOOTH;
        bacpy(&peer.rc_bdaddr, dst);
        peer.rc_channel = htobs(channel);

        int selffd = socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);

        bind(selffd, (struct sockaddr*) &self,
             sizeof(struct sockaddr_rc));

        connect(selffd, (struct sockaddr*) &peer,
                sizeof(struct sockaddr_rc));