dbus 初探版本 dbus-1.4.0

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dbus 初探版本 dbus-1.4.0

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文章出处：http://www.lt-net.cn
作者联系方式：刘敏 <qtgirl666@gmail.com>

编译系统Ubuntu10.04（确保/opt 可写）交叉编译器arm-linux-gcc 4.3.3硬件设备LT2440开发板测试软件dbus-1.4.0依赖库libxml2-2.7.6

一直以来都想学习dbus，想把dbus移植到LT2440开发板上，今天弱弱的看了一下相关的资料，编译了dbus库，并且做了一个测试。
首先，编译 libxml2-2.7.6
$ ./configure --host=arm-linux --prefix=/opt/gtkfb
$ make
$ make install
其次，编译dbus-1.4.0
需要先让dbus找到 libxml 库，使用PKG_CONFIG_PATH，使用下面的export 命令即可
$ export PKG_CONFIG_PATH=/opt/gtkfb/lib/pkgconfig
$ ./configure --host=arm-linux --prefix=/opt/gtkfb --without-x --with-xml=libxml
$ make
$ make install
这样dbus库就编译好了，并且会得到一些命令，在/opt/gtkfb/bin目录下，以dbus开头
将相关库拷贝到文件系统，拷贝以上命令到bin目录，已经移植好了，找一个程序做测试
sample.c

/*
* Example low-level D-Bus code.
* Written by Matthew Johnson <dbus@matthew.ath.cx>
*
* This code has been released into the Public Domain.
* You may do whatever you like with it.
*/
#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_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, &param)) {
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, &param);
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] [<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;
}

复制代码

makefile

CC = arm-linux-gcc
CFLAGS += -Wall -g -I/opt/gtkfb/include/dbus-1.0 -I/opt/gtkfb/lib/dbus-1.0/include
LIBS += -Wall -g -L/opt/gtkfb/lib -ldbus-1 -lpthread -lrt
TARGET = sample
OBJ = $(TARGET).o
all: $(TARGET)
%o: %c
$(CC) $(CFLAGS) -c $< -o $@
$(TARGET): $(OBJ)
$(CC) $(LIBS) -o $(TARGET) $(OBJ)

复制代码

编译后得到 sample 可执行文件，放入开发板文件系统
执行，出现如下错误，查看资料得知，需要先配置dbus才可以使用它
作如下的配置:
1.先运行dbus-daemon
$ dbus-daemon –system –print-pid –print-address
出现如下错误：Failed to start message bus: Could not get UID and GID for username “messagebus”
添加一个用户就可
$ adduser  messagebus
2.再执行sample 出现如下错误
D-Bus library appears to be incorrectly set up; failed to read machine uuid: Failed to open “/opt/gtkfb/lib/dbus/machine-id”: No such file or directory
缺少machine-id ，dbus 提供dbus-uuidgen命令产生machine-id
$ dbus-uuidgen >  /opt/gtkfb/lib/dbus/machine-id
3.再执行sample 出现如下错误
Connection Error (/opt/gtkfb/bin/dbus-launch terminated abnormally with the foll
owing error: Autolaunch requested, but X11 support not compiled in.
这个需要先获得DBUS_SESSION_BUS_ADDRESS，使用 dbus-launch命令
$ dbus-launch
DBUS_SESSION_BUS_ADDRESS=unix:path=/tmp/dbus-7dbR7xlNbT,guid=3c7319d183feacf6a4faf8160000029b
DBUS_SESSION_BUS_PID=452

$ export  DBUS_SESSION_BUS_ADDRESS=unix:path=/tmp/dbus-7dbR7xlNbT,guid=3c7319d183feacf6a4faf8160000029b
再执行sample就可以启动了

signal运行实例
运行server
$ ./sample receive  &
Listening for signals
Match rule sent

运行client
$ ./sample send  lt2440
Sending signal with value lt2440
Signal Sent
Got Signal with value lt2440

method运行实例
运行server
$ ./sample listen &
Listening for method calls

运行client
$ ./sample query lt2440
Calling remote method with luther.gliethttp.12345678
Request Sent
Method called with lt2440
Got Reply: 0, 21614

dbus在lt2440开发板上成功执行。dbus封装的程序通信比较方便，简单，高效

dbus 初探 版本 dbus-1.4.0

dbus 初探版本 dbus-1.4.0