[lttng-docs.git] / contents / using-lttng / controlling-tracing / sending-trace-data-over-the-network.md

---
id: sending-trace-data-over-the-network
---

The possibility of sending trace data over the network comes as a
built-in feature of LTTng-tools. For this to be possible, an LTTng
_relay daemon_ must be executed and listening on the machine where
trace data is to be received, and the user must create a tracing
session using appropriate options to forward trace data to the remote
relay daemon.

The relay daemon listens on two different TCP ports: one for control
information and the other for actual trace data.

Starting the relay daemon on the remote machine is as easy as:

<pre class="term">
lttng-relayd
</pre>

This will make it listen to its default ports: 5342 for control and
5343 for trace data. The `--control-port` and `--data-port` options may
be used to specify different ports.

Traces written by `lttng-relayd` are written to
<code>~/lttng-traces/<em>hostname</em>/<em>session</em></code> by
default, where <code><em>hostname</em></code> is the host name of the
traced (monitored) system and <code><em>session</em></code> is the
tracing session name. Use the `--output` option to write trace data
outside `~/lttng-traces`.

On the sending side, a tracing session must be created using the
`lttng` tool with the `--set-url` option to connect to the distant
relay daemon:

<pre class="term">
lttng create my-session --set-url net://distant-host
</pre>

The URL format is described in the output of `lttng create --help`.
The above example will use the default ports; the `--ctrl-url` and
`--data-url` options may be used to set the control and data URLs
individually.

Once this basic setup is completed and the connection is established,
you may use the `lttng` tool on the target machine as usual; everything
you do will be transparently forwarded to the remote machine if needed.
For example, a parameter changing the maximum size of trace files will
have an effect on the distant relay daemon actually writing the trace.
Commit	Line	Data
5e0cbfb0 PP	1	---
	2	id: sending-trace-data-over-the-network
	3	---
	4
	5	The possibility of sending trace data over the network comes as a
	6	built-in feature of LTTng-tools. For this to be possible, an LTTng
	7	_relay daemon_ must be executed and listening on the machine where
	8	trace data is to be received, and the user must create a tracing
	9	session using appropriate options to forward trace data to the remote
	10	relay daemon.
	11
	12	The relay daemon listens on two different TCP ports: one for control
	13	information and the other for actual trace data.
	14
	15	Starting the relay daemon on the remote machine is as easy as:
	16
	17	<pre class="term">
	18	lttng-relayd
	19	</pre>
	20
	21	This will make it listen to its default ports: 5342 for control and
	22	5343 for trace data. The `--control-port` and `--data-port` options may
	23	be used to specify different ports.
	24
	25	Traces written by `lttng-relayd` are written to
	26	<code>~/lttng-traces/<em>hostname</em>/<em>session</em></code> by
	27	default, where <code><em>hostname</em></code> is the host name of the
	28	traced (monitored) system and <code><em>session</em></code> is the
	29	tracing session name. Use the `--output` option to write trace data
	30	outside `~/lttng-traces`.
	31
	32	On the sending side, a tracing session must be created using the
	33	`lttng` tool with the `--set-url` option to connect to the distant
	34	relay daemon:
	35
	36	<pre class="term">
	37	lttng create my-session --set-url net://distant-host
	38	</pre>
	39
	40	The URL format is described in the output of `lttng create --help`.
	41	The above example will use the default ports; the `--ctrl-url` and
	42	`--data-url` options may be used to set the control and data URLs
	43	individually.
	44
	45	Once this basic setup is completed and the connection is established,
	46	you may use the `lttng` tool on the target machine as usual; everything
	47	you do will be transparently forwarded to the remote machine if needed.
	48	For example, a parameter changing the maximum size of trace files will
	49	have an effect on the distant relay daemon actually writing the trace.