1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
|
<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_bus_send"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_bus_send</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_bus_send</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_bus_send</refname>
<refname>sd_bus_send_to</refname>
<refname>sd_bus_message_send</refname>
<refpurpose>Queue a D-Bus message for transfer</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_bus_send</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
<paramdef>uint64_t *<parameter>cookie</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_bus_send_to</function></funcdef>
<paramdef>sd_bus *<parameter>bus</parameter></paramdef>
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
<paramdef>const char *<parameter>destination</parameter></paramdef>
<paramdef>uint64_t *<parameter>cookie</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int sd_bus_message_send</funcdef>
<paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_bus_send()</function> queues the bus message object <parameter>m</parameter> for
transfer. If <parameter>bus</parameter> is <constant>NULL</constant>, the bus that
<parameter>m</parameter> is attached to is used. <parameter>bus</parameter> only needs to be set when the
message is sent to a different bus than the one it is attached to, for example when forwarding messages.
If the output parameter <parameter>cookie</parameter> is not <constant>NULL</constant>, it is set to the
message identifier. This value can later be used to match incoming replies to their corresponding
messages. If <parameter>cookie</parameter> is set to <constant>NULL</constant> and the message is not
sealed, <function>sd_bus_send()</function> assumes the message <parameter>m</parameter> does not expect a
reply and adds the necessary headers to indicate this.</para>
<para>Note that in most scenarios, <function>sd_bus_send()</function> should not be called
directly. Instead, use higher level functions such as
<citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
<citerefentry><refentrytitle>sd_bus_reply_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry>
which call <function>sd_bus_send()</function> internally.</para>
<para><function>sd_bus_send_to()</function> 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
<citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry>
followed by calling <function>sd_bus_send()</function>.</para>
<para><function>sd_bus_send()</function>/<function>sd_bus_send_to()</function> 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.
<citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry> should
be invoked to write out any queued message data to the transport.</para>
<para><function>sd_bus_message_send()</function> is the same as <function>sd_bus_send()</function> but
without the first and last argument. <function>sd_bus_message_send(m)</function> is equivalent to
<function>sd_bus_send(sd_bus_message_get_bus(m), m, NULL)</function>.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, these functions return a non-negative integer. On failure, they return a negative
errno-style error code.</para>
<refsect2 id='errors'>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>The input parameter <parameter>m</parameter> is <constant>NULL</constant>.
</para>
<xi:include href="version-info.xml" xpointer="v246"/></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EOPNOTSUPP</constant></term>
<listitem><para>The bus connection does not support sending file descriptors.
</para>
<xi:include href="version-info.xml" xpointer="v246"/></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The bus connection was allocated in a parent process and is being reused in a child
process after <function>fork()</function>.</para>
<xi:include href="version-info.xml" xpointer="v246"/></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOBUFS</constant></term>
<listitem><para>The bus connection's write queue is full.</para>
<xi:include href="version-info.xml" xpointer="v246"/></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOTCONN</constant></term>
<listitem><para>The input parameter <parameter>bus</parameter> is
<constant>NULL</constant> or the bus is not connected.</para>
<xi:include href="version-info.xml" xpointer="v246"/></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ECONNRESET</constant></term>
<listitem><para>The bus connection was closed while waiting for the response.
</para>
<xi:include href="version-info.xml" xpointer="v246"/></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOMEM</constant></term>
<listitem><para>Memory allocation failed.</para>
<xi:include href="version-info.xml" xpointer="v246"/></listitem>
</varlistentry>
</variablelist>
</refsect2>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>History</title>
<para><function>sd_bus_send()</function> and
<function>sd_bus_send_to()</function> were added in version 246.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_bus_call_method</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_bus_reply_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_bus_process</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>
|
