sd_bus_send, sd_bus_send_to, sd_bus_message_send — Queue a D-Bus message for transfer
|const char *destination,|
sd_bus_send() queues the bus message object
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
cookie is set to
NULL and the message is not
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_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
followed by calling
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
be invoked to write out any queued message data to the transport.
sd_bus_message_send() is the same as
without the first and last argument.
sd_bus_message_send(m) is equivalent to
sd_bus_send(sd_bus_message_get_bus(m), m, NULL).
On success, these functions return a non-negative integer. On failure, they return a negative errno-style error code.
Returned errors may indicate the following problems:
The input parameter
The bus connection does not support sending file descriptors.
The bus connection was allocated in a parent process and is being reused in a child
The bus connection's write queue is full.
The input parameter
NULL or the bus is not connected.
The bus connection was closed while waiting for the response.
Memory allocation failed.
These APIs are implemented as a shared
library, which can be compiled and linked to with the