本文共 10887 字，大约阅读时间需要 36 分钟。
/*
* 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, ¶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] [<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; } 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 $ 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转载地址：http://kpoci.baihongyu.com/