dbus基本接口

[color=red][size=medium]/*
* Example low-level D-Bus code.
* Written by Matthew Johnson
*
* This code has been released into the Public Domain.
* You may do whatever you like with it.
*/
#include
#include
#include
#include
#include

/**
* 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_SESSION, &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
dbus_message_unref(msg);
}

/**
* Call a method on a remote object
*/
void query(char* param)
{
DBusMessage* msg;
DBusMessageIter args;
DBusConnection* conn;
DBusError err;
DBusPendingCall* pending;
int ret;
bool stat;
dbus_uint32_t level;

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_SESSION, &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
dbus_message_unref(msg);
}


void reply_to_method_call(DBusMessage* msg, DBusConnection* conn)
{
DBusMessage* reply;
DBusMessageIter args;
bool 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_SESSION, &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);
}
}


/**
* 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_SESSION, &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);
}
}


int main(int argc, char** argv)
{
if (2 > argc) {
printf ("Syntax: dbus-example [send|receive|listen|query] []\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] []\n");
return 1;
}
return 0;
}


编译
----------------------------------------------------------
错误1:
$ gcc test.c
test.c:8:23: 错误： dbus/dbus.h：No such file or directory
......
$
错误提示，dbus库的头文件位置不正确(如果已经安装了dbus的话)
$ sudo updatedb
$ sudo locate dbus.h (查看dbus.h的所在位置)
/usr/local/include/dbus-1.0/dbus/dbus.h
/usr/include/dbus-1.0/dbus/dbus.h
看来dbus.h的存放位置的确不正确，这可能是由于dbus-1.0的安装位置有问题，没关系，调整一下dbus的头文件位置就可以了(调整方法如下):
root@zxl:/usr/include# ln -sf dbus-1.0/dbus


错误2:
$ gcc test.c
在包含自 test.c：8 的文件中:
/usr/include/dbus/dbus.h:29:33: 错误： dbus/dbus-arch-deps.h：No such file or directory
......

依然有头文件无法正确定位的问题，从错误提示来看，该文件应该在/usr/include/dbus/目录下，可是进入该目录查看竟然没有，那就在整个系统中查找该文件。
root@zxl:/usr/include/dbus# locate dbus-arch-deps.h
/usr/local/lib/dbus-1.0/include/dbus/dbus-arch-deps.h
/usr/lib/dbus-1.0/include/dbus/dbus-arch-deps.h
将该文件复制到/usr/include/dbus目录下


错误3:
$ gcc test.c
......
test.c:(.text+0xbb6): undefined reference to `dbus_message_iter_get_basic'
test.c:(.text+0xbd4): undefined reference to `dbus_message_unref'
collect2: ld 返回 1

需要连接动态库dbus
$ cd /usr/lib
$ ls *dbus*
libdbus-1.a libdbus-1.so.3 libdbus-glib-1.so
libdbus-1.la libdbus-1.so.3.2.0 libdbus-glib-1.so.2
libdbus-1.so libdbus-glib-1.a libdbus-glib-1.so.2.1.0

$ gcc test.c -l dbus-1 -o dbus


执行(用普通用户身份执行)
----------------------------------------------------------
$ ./dbus receive
Listening for signals
Match rule sent
Got Signal with value luoling


$ ./dbus send luoling (再开一个标签)
Sending signal with value luoling
Signal Sent

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