sd_bus_send
systemd
sd_bus_send
3
sd_bus_send
sd_bus_send_to
sd_bus_message_send
Queue a D-Bus message for transfer
#include <systemd/sd-bus.h>
int sd_bus_send
sd_bus *bus
sd_bus_message *m
uint64_t *cookie
int sd_bus_send_to
sd_bus *bus
sd_bus_message *m
const char *destination
uint64_t *cookie
int sd_bus_message_send
sd_bus_message *m
Description
sd_bus_send() queues the bus message object m for
transfer. If bus is NULL, the bus that
m is attached to is used. bus only needs to be set when the
message is sent to a different bus than the one it's attached to, for example when forwarding messages.
If the output parameter cookie is not NULL, it is set to the
message identifier. This value can later be used to match incoming replies to their corresponding
messages. If cookie is set to NULL and the message is not
sealed, sd_bus_send() assumes the message m doesn't expect a
reply and adds the necessary headers to indicate this.
Note that in most scenarios, sd_bus_send() should not be called
directly. Instead, use higher level functions such as
sd_bus_call_method3 and
sd_bus_reply_method_return3
which call sd_bus_send() internally.
sd_bus_send_to() is a shorthand for sending a message to a specific
destination. It's main use case is to simplify sending unicast signal messages (signals that only have a
single receiver). It's behavior is similar to calling
sd_bus_message_set_destination3
followed by calling sd_bus_send().
sd_bus_send()/sd_bus_send_to() will write the message
directly to the underlying transport (e.g. kernel socket buffer) if possible. If the connection is not
set up fully yet the message is queued locally. If the transport buffers are congested any unwritten
message data is queued locally, too. If the connection has been closed or is currently being closed the
call fails.
sd_bus_process3 should
be invoked to write out any queued message data to the transport.
sd_bus_message_send() is the same as sd_bus_send() but
without the first and last argument. It's equivalent to
sd_bus_message_send(sd_bus_message_get_bus(m), m, NULL).
Return Value
On success, these functions return a non-negative integer. On failure, they return a negative
errno-style error code.
Errors
Returned errors may indicate the following problems:
-EINVAL
The input parameter m is NULL.
-EOPNOTSUPP
The bus connection does not support sending file descriptors.
-ECHILD
The bus connection was allocated in a parent process and is being reused in a child
process after fork().
-ENOBUFS
The bus connection's write queue is full.
-ENOTCONN
The input parameter bus is
NULL or the bus is not connected.
-ECONNRESET
The bus connection was closed while waiting for the response.
-ENOMEM
Memory allocation failed.
See Also
systemd1,
sd-bus3,
sd_bus_call_method3,
sd_bus_message_set_destination3,
sd_bus_reply_method_return3,
sd_bus_process3