Index · Directives systemd 250


sd_bus_set_server, sd_bus_is_server, sd_bus_get_bus_id, sd_bus_set_bus_client, sd_bus_is_bus_client, sd_bus_set_monitor, sd_bus_is_monitor — Configure connection mode for a bus object


#include <systemd/sd-bus.h>
int sd_bus_set_server(sd_bus *bus,
 int b,
 sd_id128_t id);
int sd_bus_is_server(sd_bus *bus);
int sd_bus_get_bus_id(sd_bus *bus,
 sd_id128_t *id);
int sd_bus_set_bus_client(sd_bus *bus,
 int b);
int sd_bus_is_bus_client(sd_bus *bus);
int sd_bus_set_monitor(sd_bus *bus,
 int b);
int sd_bus_is_monitor(sd_bus *bus);


sd_bus_set_server() configures the bus object as a server for direct D-Bus connections. b enables/disables the server mode. If zero, the server mode is disabled. Otherwise, the server mode is enabled. Configuring a bus object as a server is required to allow establishing direct connections between two peers without going via the D-Bus daemon. id must contain a 128-bit integer id for the server. If clients add a guid field to their D-Bus address string, the server id must match this guid or the D-Bus authentication handshake will fail. If no specific id is defined for the server, sd_id128_randomize(3) can be used to generate a random id instead.

sd_bus_is_server() returns whether the server mode is enabled for the given bus object.

sd_bus_get_bus_id() stores the D-Bus server id configured using sd_bus_set_server() (for server bus objects) or received during D-Bus authentication (for client bus objects) in id.

sd_bus_set_bus_client() configures the bus object as a D-Bus daemon client. b enables/disables the client mode. If zero, the client mode is disabled and the bus object should connect directly to a D-Bus server. Otherwise, the client mode is enabled and the bus object should connect to a D-Bus daemon. When connecting to an existing bus using any of the functions in the sd_bus_open(3) family of functions or any of the functions in the sd_bus_default(3) family of functions, the bus object is automatically configured as a bus client. However, when connecting to a D-Bus daemon by calling sd_bus_set_address(3) followed by sd_bus_start(3), the bus object should be manually configured as a bus client using sd_bus_set_bus_client(). By default, a bus object is not configured as a D-Bus daemon client.

sd_bus_is_bus_client() returns whether the client mode is enabled/disabled for the given bus object.

sd_bus_set_monitor() configures the bus object as a D-Bus monitor object. b enables/disables the monitor mode. If zero, the monitor mode is disabled. If non-zero, the monitor mode is enabled. When the monitor mode is enabled, no messages may be sent via the bus object and it may not expose any objects on the bus. To start monitoring messages, call the org.freedesktop.DBus.Monitoring.BecomeMonitor method of the D-Bus daemon and pass a list of matches indicating which messages to intercept. See The D-Bus specification for more information.

sd_bus_is_monitor() returns whether the monitor mode is enabled/disabled for the given bus object.

Return Value

On success, sd_bus_set_server(), sd_bus_get_bus_id(), sd_bus_set_bus_client() and sd_bus_set_monitor() return a non-negative integer. On failure, they return a negative errno-style error code.

sd_bus_is_server(), sd_bus_is_bus_client() and sd_bus_is_monitor() return a positive integer when the server or client mode is enabled, respectively. Otherwise, they return zero.


Returned errors may indicate the following problems:


The bus connection has been created in a different process.


The bus connection has already been started.


The bus cannot be resolved.


A required parameter was NULL or b was zero and id did not equal SD_ID128_NULL.


The bus is not connected.


These APIs are implemented as a shared library, which can be compiled and linked to with the libsystemd pkg-config(1) file.

See Also

systemd(1), sd-bus(3)