dbus

[Aashish Raina]

The problem is solved now.

There are few doubts  regarding this small application

1:i have a   sender_signal   application (which sends a signal)

2: one rec_signal  application (which will rec it)

     Problem is that the receiver when comparing the interface from which 
the signal is coming ,,after providing the right interface it is not going 
into the if condition

     in rec _signal application  when i am comparing
     whether the signal has come from the same interface   it does not go 
into the loop.

     if (dbus_message_is_signal(msg, "org.pirate.parrot.Type", "Feathers")) 
//interface and signal
      {

       }
   else
      {

      }
          goes in the else part


3:   This function is not working says undefined refrence in my 
receiver_signal application :->      dbus_message_iter_get_basic(&args, 
&sigvalue);
      is there any other function which helps me to get the signal


4: when we send signal what does it actually mean ,does it mean just a 
string being passed from server to client (it is not a function )


This is sender_signal  in one file

 main()
{
  DBusError error,error2;
  DBusConnection *conn;

  //dbus_uint32_t serial = 0; // unique number to associate replies with 
requests
  DBusMessage* msg;
  DBusMessageIter args;

  dbus_error_init (&error);
 conn = dbus_bus_get (DBUS_BUS_SYSTEM, &error);

 if (!conn)
   {
     fprintf (stderr, "%s: %s\n",
              error.name, error.message);
     return 1;
   }
 else
   printf("%p",conn);

 //now sending a message but from a well known address :lets accuire a 
service

 //Connecting to the system bus is a nice first step, but we want to be able 
to send messages from a well-known address. Let's acquire a service:


 dbus_bus_acquire_service (conn, "org.pirate.parrot",0, &error2);
 //dbus_bus_acquire_service (conn, "org.freedesktop.DBus",0, &error2);

 if (dbus_error_is_set (&error2))
   {
     fprintf (stderr, "%s: %s\n",
              error2.name, error2.message);
     printf("\nentred into the error\n");
     //dbus_connection_disconnect (conn);
     //return;
   }


 //DBusMessage *msg;
 DBusMessageIter iter;

 /* create a new message of type signal */
 msg = dbus_message_new_signal(
                               "org/pirate/parrot/Object",
                               "org.pirate.parrot.Type", "Feathers");


 if (NULL == msg)
   {
     fprintf(stderr, "Message Null\n");
     exit(1);
   }
 else
   printf("created");

 //let us not give ant parameter to signal

 /* build the signal's payload up */

 dbus_message_iter_init (msg, &iter);
 dbus_message_iter_append_string (&iter, "Shiny");
 dbus_message_iter_append_string (&iter,
                                  "Well Groomed");


 /* send the message */
 if (!dbus_connection_send (conn, msg, NULL))
 fprintf (stderr, "error sending message\n");
 else
   printf("message send");
 /* drop the reference count on the message */
 //dbus_message_unref (msg);

 /* flush the connection buffer */
 dbus_connection_flush (conn);
///////////////////////////////////////////////////////////////////////////////////////////////////////

this is receiver waiting for signal   in another file
main()
{
  DBusMessage* msg;
  DBusMessageIter args;
  DBusConnection* conn;
  DBusError err,error2;
  int ret;
  char* sigvalue;

  printf("Listening for signals\n");

  // initialise the errors
  dbus_error_init(&err);

  // connect to the bus and check for errors
  conn = dbus_bus_get(DBUS_BUS_SYSTEM, &err);
  printf("%p",conn);
  if (dbus_error_is_set(&err)) {
    fprintf(stderr, "Connection Error (%s)\n", err.message);
    dbus_error_free(&err);
  }
  if (NULL == conn) {
    exit(1);
  }

  /*
  // request our name on the bus and check for errors
  ret = dbus_bus_request_name(conn, "test.signal.sink", 
DBUS_NAME_FLAG_REPLACE_EXISTING , &err);
  if (dbus_error_is_set(&err)) {
  fprintf(stderr, "Name Error (%s)\n", err.message);
  dbus_error_free(&err);
  }
  if (DBUS_REQUEST_NAME_REPLY_PRIMARY_OWNER != ret) {
  exit(1);
  }
  */
  //create a object for communication


  dbus_bus_acquire_service (conn, "org.pirate.parrot_rec",0, &error2);



  // add a rule for which messages we want to see
  dbus_bus_add_match(conn, 
"type='signal',interface='org.pirate.parrot.Type'", &err); // see signals 
from the given interface

  //dbus_connection_flush(conn);

 if (dbus_error_is_set(&err)) {
    fprintf(stderr, "Match Error (%s)\n", err.message);
    exit(1);
  }
  else
    printf("Match rule sent\n");

  // loop listening for signals being emmitted
  while (true) {

    printf("\nwelcome\n");
    // non blocking read of the next available message

    //  dbus_connection_read_write(conn, 0); this is not working

    msg = dbus_connection_pop_message(conn);  //gets the first mesage from 
the queue

    // loop again if we haven't read a message
    if (NULL == msg) {
      sleep(1);
      continue;
    }
    else
      printf("\n message aaya\n");
    // check if the message is a signal from the correct interface and with 
the correct name

   if (dbus_message_is_signal(msg, "org.pirate.parrot.Type", "Feathers")) 
//interface and signal (feathers)

      {
        printf("\nfound the  interface\n");
        // read the parameters
        if (!dbus_message_iter_init(msg, &args))
          fprintf(stderr, "Message Has No Parameters\n");
        else if (DBUS_TYPE_STRING != dbus_message_iter_get_arg_type(&args))
          fprintf(stderr, "Argument is not string!\n");
        else
          {
            printf("\nentered else\n ");
          }
        printf("\n(args)%p\n",args);
        dbus_message_iter_get_basic(&args, &sigvalue);
        //printf("Got Signal with value %s\n", sigvalue);
      }

      /*else
      {
      printf("\nprob with the interface\n");
      }*/

        // free the message
        dbus_message_unref(msg);
}
} 


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