D-Bus Basic Overview: http://pythonhosted.org/txdbus/dbus_overview.html
The Installation Guide: http://www.linuxfromscratch.org/blfs/view/svn/general/dbus.html
The Introduction to D-Bus ( more details ) : http://www.freedesktop.org/wiki/IntroductionToDBus/
The D-Bus Tutorial: http://dbus.freedesktop.org/doc/dbus-tutorial.html
D-Bus APIs: http://dbus.freedesktop.org/doc/api/html/
Example Source: http://www.matthew.ath.cx/misc/dbus
I use the example: dbus-example.c from the above source and modify a little bit for bug fixed. And also, here is my test conf file for the permission of using the system bus.
- dbus-example.c
#define DBUS_API_SUBJECT_TO_CHANGE
#include <dbus/dbus.h>
#include <stdbool.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
/**
* Connect to the DBUS bus and send a broadcast signal
*/
void sendsignal(char* sigvalue)
{
DBusMessage* msg;
DBusMessageIter args;
DBusConnection* conn;
DBusError err;
int ret;
dbus_uint32_t serial = 0;
printf("Sending signal with value %s\n", sigvalue);
// initialise the error value
dbus_error_init(&err);
// connect to the DBUS system bus, and check for errors
conn = dbus_bus_get(DBUS_BUS_SYSTEM, &err);
if (dbus_error_is_set(&err)) {
fprintf(stderr, "Connection Error (%s)\n", err.message);
dbus_error_free(&err);
}
if (NULL == conn) {
exit(1);
}
// register our name on the bus, and check for errors
ret = dbus_bus_request_name(conn, "test.signal.source", 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 signal & check for errors
msg = dbus_message_new_signal("/test/signal/Object", // object name of the signal
"test.signal.Type", // interface name of the signal
"Test"); // name of the signal
if (NULL == msg)
{
fprintf(stderr, "Message Null\n");
exit(1);
}
// append arguments onto signal
dbus_message_iter_init_append(msg, &args);
if (!dbus_message_iter_append_basic(&args, DBUS_TYPE_STRING, &sigvalue)) {
fprintf(stderr, "Out Of Memory!\n");
exit(1);
}
// send the message and flush the connection
if (!dbus_connection_send(conn, msg, &serial)) {
fprintf(stderr, "Out Of Memory!\n");
exit(1);
}
dbus_connection_flush(conn);
printf("Signal Sent\n");
// free the message and close the connection
dbus_message_unref(msg);
dbus_connection_close(conn);
}
/**
* Call a method on a remote object
*/
void query(char* param)
{
DBusMessage* msg;
DBusMessageIter args;
DBusConnection* conn;
DBusError err;
DBusPendingCall* pending;
int ret;
dbus_bool_t stat = FALSE;
dbus_uint32_t level = 0;
printf("Calling remote method with %s\n", param);
// initialiset the errors
dbus_error_init(&err);
// connect to the system bus and check for errors
conn = dbus_bus_get(DBUS_BUS_SYSTEM, &err);
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
ret = dbus_bus_request_name(conn, "test.method.caller", 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 new method call and check for errors
msg = dbus_message_new_method_call("test.method.server", // target for the method call
"/test/method/Object", // object to call on
"test.method.Type", // interface to call on
"Method"); // method name
if (NULL == msg) {
fprintf(stderr, "Message Null\n");
exit(1);
}
// append arguments
dbus_message_iter_init_append(msg, &args);
if (!dbus_message_iter_append_basic(&args, DBUS_TYPE_STRING, ¶m)) {
fprintf(stderr, "Out Of Memory!\n");
exit(1);
}
// send message and get a handle for a reply
if (!dbus_connection_send_with_reply (conn, msg, &pending, -1)) { // -1 is default timeout
fprintf(stderr, "Out Of Memory!\n");
exit(1);
}
if (NULL == pending) {
fprintf(stderr, "Pending Call Null\n");
exit(1);
}
dbus_connection_flush(conn);
printf("Request Sent\n");
// free message
dbus_message_unref(msg);
// block until we recieve a reply
dbus_pending_call_block(pending);
// get the reply message
msg = dbus_pending_call_steal_reply(pending);
if (NULL == msg) {
fprintf(stderr, "Reply Null\n");
exit(1);
}
// free the pending message handle
dbus_pending_call_unref(pending);
// read the parameters
if (!dbus_message_iter_init(msg, &args))
fprintf(stderr, "Message has no arguments!\n");
else if (DBUS_TYPE_BOOLEAN != dbus_message_iter_get_arg_type(&args))
fprintf(stderr, "Argument is not boolean!\n");
else
dbus_message_iter_get_basic(&args, &stat);
if (!dbus_message_iter_next(&args))
fprintf(stderr, "Message has too few arguments!\n");
else if (DBUS_TYPE_UINT32 != dbus_message_iter_get_arg_type(&args))
fprintf(stderr, "Argument is not int!\n");
else
dbus_message_iter_get_basic(&args, &level);
printf("Got Reply: %d, %d\n", stat, level);
// free reply and close connection
dbus_message_unref(msg);
dbus_connection_close(conn);
}
void reply_to_method_call(DBusMessage* msg, DBusConnection* conn)
{
DBusMessage* reply;
DBusMessageIter args;
dbus_bool_t stat = TRUE;
dbus_uint32_t level = 21614;
dbus_uint32_t serial = 0;
char* param = "";
// read the arguments
if (!dbus_message_iter_init(msg, &args))
fprintf(stderr, "Message has no arguments!\n");
else if (DBUS_TYPE_STRING != dbus_message_iter_get_arg_type(&args))
fprintf(stderr, "Argument is not string!\n");
else
dbus_message_iter_get_basic(&args, ¶m);
printf("Method called with %s\n", param);
// create a reply from the message
reply = dbus_message_new_method_return(msg);
// add the arguments to the reply
dbus_message_iter_init_append(reply, &args);
if (!dbus_message_iter_append_basic(&args, DBUS_TYPE_BOOLEAN, &stat)) {
fprintf(stderr, "Out Of Memory!\n");
exit(1);
}
if (!dbus_message_iter_append_basic(&args, DBUS_TYPE_UINT32, &level)) {
fprintf(stderr, "Out Of Memory!\n");
exit(1);
}
// send the reply && flush the connection
if (!dbus_connection_send(conn, reply, &serial)) {
fprintf(stderr, "Out Of Memory!\n");
exit(1);
}
dbus_connection_flush(conn);
// free the reply
dbus_message_unref(reply);
}
/**
* Server that exposes a method call and waits for it to be called
*/
void listen()
{
DBusMessage* msg;
DBusMessage* reply;
DBusMessageIter args;
DBusConnection* conn;
DBusError err;
int ret;
char* param;
printf("Listening for method calls\n");
// initialise the error
dbus_error_init(&err);
// connect to the bus and check for errors
conn = dbus_bus_get(DBUS_BUS_SYSTEM, &err);
if (dbus_error_is_set(&err)) {
fprintf(stderr, "Connection Error (%s)\n", err.message);
dbus_error_free(&err);
}
if (NULL == conn) {
fprintf(stderr, "Connection Null\n");
exit(1);
}
// request our name on the bus and check for errors
ret = dbus_bus_request_name(conn, "test.method.server", 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) {
fprintf(stderr, "Not Primary Owner (%d)\n", ret);
exit(1);
}
// loop, testing for new messages
while (true) {
// non blocking read of the next available message
dbus_connection_read_write(conn, 0);
msg = dbus_connection_pop_message(conn);
// loop again if we haven't got a message
if (NULL == msg) {
sleep(1);
continue;
}
// check this is a method call for the right interface & method
if (dbus_message_is_method_call(msg, "test.method.Type", "Method"))
reply_to_method_call(msg, conn);
// free the message
dbus_message_unref(msg);
}
// close the connection
dbus_connection_close(conn);
}
/**
* Listens for signals on the bus
*/
void receive()
{
DBusMessage* msg;
DBusMessageIter args;
DBusConnection* conn;
DBusError err;
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);
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);
//}
// add a rule for which messages we want to see
dbus_bus_add_match(conn, "type='signal',interface='test.signal.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);
}
printf("Match rule sent\n");
// loop listening for signals being emmitted
while (true) {
// non blocking read of the next available message
dbus_connection_read_write(conn, 0);
msg = dbus_connection_pop_message(conn);
// loop again if we haven't read a message
if (NULL == msg) {
sleep(1);
continue;
}
// check if the message is a signal from the correct interface and with the correct name
if (dbus_message_is_signal(msg, "test.signal.Type", "Test")) {
// 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
dbus_message_iter_get_basic(&args, &sigvalue);
printf("Got Signal with value %s\n", sigvalue);
}
// free the message
dbus_message_unref(msg);
}
// close the connection
dbus_connection_close(conn);
}
int main(int argc, char** argv)
{
if (2 > argc) {
printf ("Syntax: dbus-example [send|receive|listen|query] [<param>]\n");
return 1;
}
char* param = "no param";
if (3 >= argc && NULL != argv[2]) param = argv[2];
if (0 == strcmp(argv[1], "send"))
sendsignal(param);
else if (0 == strcmp(argv[1], "receive"))
receive();
else if (0 == strcmp(argv[1], "listen"))
listen();
else if (0 == strcmp(argv[1], "query"))
query(param);
else {
printf ("Syntax: dbus-example [send|receive|listen|query] [<param>]\n");
return 1;
}
return 0;
}
- mytesting.conf
<!DOCTYPE busconfig PUBLIC
"-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
"http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
<busconfig>
<!-- Only root or user testing can own the testing service -->
<policy user="liudanny">
<allow own="test.signal.source"/>
<allow own="test.signal.sink"/>
<allow own="test.method.server"/>
<allow own="test.method.caller"/>
</policy>
<policy user="root">
<allow own="test.signal.source"/>
<allow own="test.signal.sink"/>
<allow own="test.method.server"/>
<allow own="test.method.caller"/>
</policy>
<!-- Allow anyone to invoke methods on testing server -->
<policy context="default">
<allow send_destination="test.signal.source"/>
<allow receive_sender="test.signal.source"/>
</policy>
<policy context="default">
<allow send_destination="test.signal.sink"/>
<allow receive_sender="test.signal.sink"/>
</policy>
<policy context="default">
<allow send_destination="test.method.server"/>
<allow receive_sender="test.method.server"/>
</policy>
<policy context="default">
<allow send_destination="test.method.caller"/>
<allow receive_sender="test.method.caller"/>
</policy>
<!-- Allow everything, including access to SetHostName to users of the group "liudanny" -->
<policy group="liudanny">
<allow send_destination="test.signal.source"/>
<allow receive_sender="test.signal.source"/>
</policy>
<policy user="root">
<allow send_destination="test.signal.source"/>
<allow receive_sender="test.signal.source"/>
</policy>
<policy group="liudanny">
<allow send_destination="test.signal.sink"/>
<allow receive_sender="test.signal.sink"/>
</policy>
<policy user="root">
<allow send_destination="test.signal.sink"/>
<allow receive_sender="test.signal.sink"/>
</policy>
<policy group="liudanny">
<allow send_destination="test.method.server"/>
<allow receive_sender="test.method.server"/>
</policy>
<policy user="root">
<allow send_destination="test.method.server"/>
<allow receive_sender="test.method.server"/>
</policy>
<policy group="liudanny">
<allow send_destination="test.method.caller"/>
<allow receive_sender="test.method.caller"/>
</policy>
<policy user="root">
<allow send_destination="test.method.caller"/>
<allow receive_sender="test.method.caller"/>
</policy>
</busconfig>
