Dbus - Did not receive a reply

Question

I have a strange issue with Dbus...
I use Dbus-1.
The issue is, that it only happens sometimes and at different parts. Sometimes for IDAMsg_GetFontName, sometimes for IDAMsg_GetForeColor (e.g). Maybe the program runs ten times fine, then one time with error. Or four times fine, then two times with error.

But it is always the same error message from my std::cout and Dbus:

Too few arguments

and

Did not receive a reply

But how can I have sometimes too few arguments?
And how can give Dbus this error message, as it looks, that a reply was send and got?

Help is really appreciated.
TIA
Earlybite

The Dbus message is:

Did not receive a reply. Possible causes include: the remote 
application did not send a reply, the message bus security policy 
blocked the reply, the reply timeout expired, or the network 
connection was broken.

The sending of a method:

if(vMethod == IDAMsg_Init || vMethod == IDAMsg_GetFontName
|| vMethod == IDAMsg_AppQuit
|| vMethod == IDAMsg_GetBackColor || vMethod == IDAMsg_GetForeColor
|| vMethod == IDAMsg_GetBorderColor){
    dbus_message_iter_init_append(msg, &args);
    if (!dbus_message_iter_append_basic(&args, DBUS_TYPE_STRING, &vMsg.Str_Send[0])) {
         cout << "DBUS -- SEND -- OUT OF MEMORY 1" << endl; return 0;
    }
    if(vMethod == IDAMsg_GetBorderColor || vMethod == IDAMsg_AppQuit){
        if (!dbus_message_iter_append_basic(&args, DBUS_TYPE_STRING, &vMsg.Str_Send[1])) {
             cout << "DBUS -- SEND -- OUT of Memory 2" << endl; return 0;
        }
    }
}

The reply is:

if(vMethod == IDAMsg_Init || vMethod == IDAMsg_AppQuit
|| vMethod == IDAMsg_GetFontName
|| vMethod == IDAMsg_GetBackColor || vMethod == IDAMsg_GetForeColor
|| vMethod == IDAMsg_GetBorderColor){
    if (DBUS_TYPE_STRING != dbus_message_iter_get_arg_type(&args)){
         cout << "DBUS -- REPLY -- ARG is not String 1 " << endl;
    } else {
         dbus_message_iter_get_basic(&args, &nStr_In[0]);
    }
    if(vMethod == IDAMsg_GetBorderColor || vMethod == IDAMsg_AppQuit){
        if (!dbus_message_iter_next(&args)){
             cout << "DBUS -- REPLY -- Message has too few arguments 1" << endl;
        } else if (DBUS_TYPE_STRING != dbus_message_iter_get_arg_type(&args)){
             cout << "DBUS -- REPLY -- Argument is not STRING 2" << endl;
        } else {
             dbus_message_iter_get_basic(&args, &nStr_In[1]);
        }
    }
    reply = dbus_message_new_method_return(msg);
    dbus_message_iter_init_append(reply, &args);
}
if(vMethod == IDAMsg_Init){
    if (!dbus_message_iter_append_basic(&args, DBUS_TYPE_BOOLEAN, &stat)) {
         cout << "DBUS -- REPLY -- OUT of Memory 1" << endl; return;
    }
    if (!dbus_message_iter_append_basic(&args, DBUS_TYPE_UINT32, &level)) {
         cout << "DBUS -- REPLY -- OUT of Memory 2" << endl; return;
    }
}

The std::cout output normally is:

DBUS -- EBIDA_IDA_Server -- Method Reply for : GetForeColor
DBUS -- IDABrowse -- Got Reply  245_245_245 21614
IDA -- IDABrowse -- INCOMING CALLBACK : GetBorderColor
DBUS -- IDABrowse -- Request send with : GetBorderColor
DBUS -- EBIDA_IDA_Server -- Method Reply for : GetBorderColor
DBUS -- IDABrowse -- Got Reply  102_143_165 21614
IDA -- IDABrowse -- INCOMING CALLBACK : GetBorderColor
DBUS -- IDABrowse -- Request send with : GetBorderColor
DBUS -- EBIDA_IDA_Server -- Method Reply for : GetBorderColor
DBUS -- IDABrowse -- Got Reply  126_177_204 21614
IDA -- IDABrowse -- INCOMING CALLBACK : GetBorderColor
DBUS -- IDABrowse -- Request send with : GetBorderColor
DBUS -- EBIDA_IDA_Server -- Method Reply for : GetBorderColor
DBUS -- IDABrowse -- Got Reply  148_207_239 21614

But if something went wrong it looks something like this:

DBUS -- EBIDA_IDA_Server -- Method Reply for : GetForeColor
DBUS -- IDABase -- Got Reply  245_245_245 21614
IDA -- IDABase -- INCOMING CALLBACK : GetBorderColor
DBUS -- EBIDA_IDA_Server -- Method Reply for : GetBorderColor
DBUS -- IDABase -- Request send with : GetBorderColor
DBUS --  SEND -- Message has too few arguments 1
DBUS -- IDABase -- Got Reply  Did not receive a reply. Possible 
causes include: the remote application did not send a reply, the 
message bus security policy blocked the reply, the reply timeout 
expired, or the network connection was broken. 32723

---

EDIT:

I think the issue is shown with this:

This is the normal order for output:

IDA -- IDABrowse -- INCOMING CALLBACK : GetBorderColor
DBUS -- IDABrowse -- Request sending with : GetBorderColor
DBUS -- EBIDA_IDA_Server -- Method Reply for : GetBorderColor
DBUS -- IDABrowse -- Got Reply  126_177_204 21614

This when an error occurs:

IDA -- IDABrowse -- INCOMING CALLBACK : GetBorderColor
DBUS -- EBIDA_IDA_Server -- Method Reply for : GetBorderColor
DBUS -- IDABrowse -- Request sending with : GetBorderColor
DBUS -- IDABrowse -- Got Reply  126_177_204 21614

If error, line 2 and 3 have changed.
Than, the reply exist before request sending...

Answer 1

The way to debug this is to use dbus-monitor or Bustle to look at what the traffic (requests, replies, errors) is on the bus. That should pinpoint the error and show you what message is causing it.