Pair and connect new devices using Bluez5 DBUS API with C

Question

I have an Intel Edison with the latest Board software is latest available, and I am developing a bluetooth driver using the Eclipse based IDE. My Bluez version number in this edison release is 5.37. I am writing it for a system that scans for bluetooth devices nearby, detects sensor devices based on name and MAC address, pairs and connects sensor devices automatically.

But pairing and connecting has been a problem since I can detect sensor devices but I am unable to pair them through the bluez5 interface. I have tried using the D-BUS interface and its no good as I keep getting the following error message:

Method "FindAdapter" with signature "s" on interface "org.bluez.Manager" doesn't exist

Here's the code:

DBusMessage *msg, *reply;
DBusError err;
const char *reply_path;
char *path;

msg = dbus_message_new_method_call("org.bluez", "/","org.bluez.Manager", "FindAdapter");
dbus_message_append_args(msg, DBUS_TYPE_STRING, &adapter,DBUS_TYPE_INVALID);
dbus_error_init(&err);
reply = dbus_connection_send_with_reply_and_block(conn, msg, -1, &err);
dbus_message_unref(msg);

P.S. - 
DBusConnection *conn -> DBUS_BUS_SYSTEM
const char *adapter -> "hci0".

Answer 1

Although high-level APIs like Qt5, which also uses bluez underneath could be more straightforward to use, you should still be able to do what you're attempting. Pair and Connect are associated with the device-api.txt. To call these methods you can send dbus messages as in your code or build a Proxy object with the following parameters:

name : "org.bluez"

interface "org.bluez.Device1"

path : "/org/bluez/dev_AA_BB_CC_DD_EE" where AA_BB_CC_DD_EE is your device mac address.

If you choose to build a proxy object, you can call methods like Pair or Connect through the proxy.

And, I understand that you want to find which adapter to use (because of your "FindAdapter" method) however it seems you already know that your adapter name is "hci0".

Looking at the official documentation (https://git.kernel.org/cgit/bluetooth/bluez.git/tree/doc), I was able to find the following, which specifies that the interface was dropped in 2012: https://git.kernel.org/cgit/bluetooth/bluez.git/commit/doc?id=86a7b07c22f3a595ba3c48092359287905bf0878

I also noticed you were using the DBus low-level API, as advised by freedesktop themselves (read at the bottom of the page here: https://dbus.freedesktop.org/doc/api/html/group__DBus.html ), it's a complex API used for creating bindings in other languages or you can switch to GLib GDBus for a simpler API.