dbus message not received at client from server

[Calvin Lee]

Anitha,

Yes, there is a reason that your callback is not called. The reason is
the status is by default `DBUS_DISPATCH_DATA_REMAINS`. Therefore one
must dispatch until the status changes to `DBUS_STATUS_COMPLETE`
before the callback is called for the first time.

This is shown in the code snipped that I sent. In my program I
initialize my dispatch status flag as `static bool should_dispatch =
true;` which shows that `dbus_connection_dispatch` should be called
immediately.

Perhaps this should be mentioned in documentation somewhere, because
it was not obvious to me and I dealt with this problem as well.

Best of luck,
Calvin

On Wed, Nov 22, 2017 at 11:50 PM, Anitha Chandrasekar
<anitha.chandrasekar at sasken.com> wrote:
> Hi All,
>
> As said below,
> `dbus_connection_set_dispatch_status_function` is only called if the status is changed
>
> Here the " dispatch_status" callback is set calling, dbus_connection_set_dispatch_status_function(conn, dispatch_status,        NULL, NULL);
>
> we see that this callback is not being called, even when the data is available. This happens only in certain case, rest of time this code is working fine.
>
> (Since we see that using dbus-monitor that the message is sent , but this status has not changed
> dbus-monitor logs->
> error time=1509954378.310314 sender=:1.3 -> destination=:1.12 error_name=org.bluez.Error.Failed reply_serial=52
>    string "Not connected" ).
>
> -> Please refer to this link(sample reference code of gdbus library of bluez stack),
> https://kernel.googlesource.com/pub/scm/bluetooth/bluez/+/5.9/gdbus/mainloop.c
>
> Any idea why this status callback not called, even when the message is sent from dbus sender?
>
> Regards,
> Anitha
>
> ________________________________________
> From: dbus [dbus-bounces at lists.freedesktop.org] on behalf of Calvin Lee [cyrus296 at gmail.com]
> Sent: Tuesday, November 21, 2017 9:05 PM
> To: dbus at lists.freedesktop.org
> Subject: Re: dbus message not received at client from server
>
> Anitha,
> I'm not sure if I can fix your problem with the information given, but
> I'll try to help out. Setting up DBus to be asynchronous requires more
> than using `dbus_connection_set_dispatch`. First, both DBusWatch[1] and
> DBusTimeout[2] must be honored. Second, the
> `dbus_connection_set_dispatch_status_function` is only called if the
> status is changed, it does not dispatch anything. In order to dispatch
> one must call `dbus_connection_dispatch` as many times as needed. See my
> implementation below:
> ```C static bool should_dispatch = true;
> static void dispatch_status(DBusConnection *connection,
> DBusDispatchStatus new_status,
>                 void *_data) {
>         if (new_status == DBUS_DISPATCH_DATA_REMAINS) {
>                 should_dispatch = true;
>          }
> }
> void dispatch_dbus() {
>         if (!should_dispatch || !conn) {
>                 return;
>         }
>         DBusDispatchStatus status;
>         do {
>                 status = dbus_connection_dispatch(conn);
>         } while (status == DBUS_DISPATCH_DATA_REMAINS);
>         if (status != DBUS_DISPATCH_COMPLETE) {
>                 log(L_ERROR, "Cannot dispatch dbus events: %d", status);
>         }
>         should_dispatch = false;
> }
> ```
> I call `dispatch_dbus` each time the main loop runs.
> Also `dispatch_status` is the callback to
> `dbus_connection_set_dispatch_function`.
>
> Best of luck with your project, if you need any more help please reply
> with more information.
>
> Regards,
> Calvin
>
> [1]https://dbus.freedesktop.org/doc/api/html/group__DBusWatch.html
> [2]https://dbus.freedesktop.org/doc/api/html/group__DBusTimeout.html
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-- 

-Calvin Lee