Bluetooth connection hangs after some retries (reset required/possible?)

[Manuel Reimer <mail+linux-bluetooth@m-reimer.de>]

Hello,

I'm still doing my first steps with bluetooth on Linux...

I'm trying to get HID reports of a bluetooth game controller (PS4 
gamepad). The relevant lines:

char dest[18] = "XX:XX:XX:XX:XX:XX";
int int_socket = socket(AF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP);
struct sockaddr_l2 addr = { 0 };
addr.l2_family = AF_BLUETOOTH;
str2ba( dest, &addr.l2_bdaddr );
addr.l2_psm = htobs(L2CAP_PSM_HIDP_INTR);
connect(int_socket, (struct sockaddr *)&addr, sizeof(addr));
char buf[79] = { 0 };
int bytes_read;
bytes_read = recv(int_socket, buf, sizeof(buf), 0);
while(1) {
   if( bytes_read > 0 ) {
     printf("received [%s]\n", buf);
   }
}

Yes, I do proper initialization and yes, my "real code" has error handling.

If I run this code for the first time (currently I have the "hidp" 
module blacklisted to get sure I'm really the first user of the device), 
then everything works as expected. Initialization is done and lines are 
running through console.

Sometimes I'm able to Ctrl+C and restart *once* but it never is possible 
to do a third try. If I do so, then the "read" just hangs forever. This 
also happens if I disconnect the bluetooth device and reconnect it. I 
have to "systemctl restart bluetooth" in this case to get a new chance.

What is happening here? For me it seems like the bluetooth daemon 
"somehow" does some kind of "deadlocking". Maybe the controller keeps 
sending and noone takes the messages which causes the daemon to deadlock?

How to get around this? Is it actually possible to get this stable? Is 
there, for example, some command, I can send, so whatever hangs here is 
reset?

Thank you for every answer...

Best regards,

Manuel