DBUS发送接收数据（上）

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1、Server端
testdbus_s.c

#define DBUS_API_SUBJECT_TO_CHANGE
#include <dbus/dbus.h>
#include <stdbool.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

/**
 * Wait for signals on the bus and reply
 */
void receive()
{
  DBusMessage* msg;
  DBusMessageIter args;
  DBusConnection* conn;
  DBusError err;
  int ret;
  char* sigvalue;
  int loop=1;

  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, "neohope.dbus.signal.target", 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='neohope.dbus.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 (loop) {

     // 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, "neohope.dbus.signal.Type", "TestSignal")) {
        
        // 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);
        
        if(strcmp("Bye",sigvalue)==0) {
           loop = 0;
           printf("Bye......\n");
        }
        else {
          printf("Got Signal with value: %s\n", sigvalue);
        }
     }

     // free the message
     dbus_message_unref(msg);
  }
  // do not close the connection
  // dbus_connection_close(conn);
}

/**
 * Deal with remote method call 
 */
int reply_to_method_call(DBusMessage* msg, DBusConnection* conn)
{
  DBusMessage* reply;
  DBusMessageIter args;
  int stat = 1;
  int ret = 1;
  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);

  if(strcmp("Bye",param)==0){
    ret = 0;
    printf ("Bye......\n");
  }
  else {
    printf("Method Invoked with value: %s\n", sigvalue);
  }

  // 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);
  
  return ret;
}

/**
 * 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 loop = 1;
  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, "neohope.dbus.method.provider", 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 (loop) {
     // 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, "neohope.dbus.method.Type", "TestMethod")) 
        loop = reply_to_method_call(msg, conn);

     // free the message
     dbus_message_unref(msg);
  }

  // do not close the connection
  // dbus_connection_close(conn);
}

int main(int argc, char** argv)
{
  if (2 > argc) {
     printf ("Syntax: testdbus_s [receive|listen] [<param>]\n");
     return 1;
  }
  char* param = "no param";
  if (3 >= argc && NULL != argv[2]) param = argv[2];

  if (0 == strcmp(argv[1], "receive"))
     receive();
  else if (0 == strcmp(argv[1], "listen"))
     listen();
  else {
     printf ("Syntax: testdbus_s [receive|listen] [<param>]\n");
     return 1;
  }
  return 0;
}

2、Client端
testdbus_c.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, "neohope.dbus.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("/neohope/dbus/signal/Object", // object name of the signal
                                "neohope.dbus.signal.Type", // interface name of the signal
                                "TestSignal"); // 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);
  // do not close the connection
  // 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;
  int 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_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, "neohope.dbus.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("neohope.dbus.method.provider", // target for the method call
                                     "/neohope/dbus/method/Object", // object to call on
                                     "neohope.dbus.method.Type", // interface to call on
                                     "TestMethod"); // 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 and close connection
  dbus_message_unref(msg);   
  //dbus_connection_close(conn);
}

int main(int argc, char** argv)
{
  if (2 > argc) {
     printf ("Syntax: testdbus_c [send|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], "query"))
     query(param);
  else {
     printf ("Syntax: testdbus_c [send|query] [<param>]\n");
     return 1;
  }
  return 0;
}

3、Makefile

CC=gcc
LDFLAGS+=-ldbus-1
CFLAGS+=-I/usr/include/dbus-1.0 -I/usr/lib/x86_64-linux-gnu/dbus-1.0/include/

all:testdbus_c.bin testdbus_s.bin

testdbus_c.bin:testdbus_c.o
	$(CC) $(LDFLAGS) -o testdbus_c.bin testdbus_c.o 

testdbus_c.o:testdbus_c.c
	$(CC) $(CFLAGS) -c -o testdbus_c.o testdbus_c.c 

testdbus_s.bin:testdbus_s.o
	$(CC) $(LDFLAGS) -o testdbus_s.bin testdbus_s.o 

testdbus_s.o:testdbus_s.c
	$(CC) $(CFLAGS) -c -o testdbus_s.o testdbus_s.c 

clean:
	rm *.o *.bin

4、编译

make

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