The in_tcp Input plugin enables Fluentd to accept TCP payload.

Don't use this plugin for receiving logs from client libraries. Use in_forward for such cases.

Example Configuration

in_tcp is included in Fluentd's core. No additional installation process is required.

  @type tcp
  tag # required
  format /^(?<field1>\d+):(?<field2>\w+)$/ # required
  port 20001 # optional. 5170 by default
  bind # optional. by default
  delimiter \n # optional. \n (newline) by default

Please see the Config File article for the basic structure and syntax of the configuration file.

We\'ve observed the drastic performance improvements on Linux, with proper kernel parameter settings. If you have high-volume TCP traffic, please make sure to follow the instruction described at Before Installing Fluentd.


type (required)

The value must be tcp.

tag (required)

tag of output events.


The port to listen to. Default Value = 5170


The bind address to listen to. Default Value =


The payload is read up to this character. By default, it is "\n".


The field name of the client's hostname. If set the value, the client's hostname will be set to its key. The default is nil (no adding hostname).

If you set following configuration:

source_hostname_key client_host

then the client's hostname is set to client_host field.

    "foo": "bar",
    "client_host": ""

format (required)

The format of the TCP payload. Here is the example by regular expression.

format /^(?<field1>\d+):(?<field2>\w+)$/

If you execute following command:

$ echo '123456:awesome' | netcat 5170

then got parsed result like below:


in_tcp uses parser plugin to parse the payload. See parser article for more detail.

log_level option

The log_level option allows the user to set different levels of logging for each plugin. The supported log levels are: fatal, error, warn, info, debug, and trace.

Please see the logging article for further details.

If this article is incorrect or outdated, or omits critical information, please let us know. Fluentd is a open source project under Cloud Native Computing Foundation (CNCF). All components are available under the Apache 2 License.

Last updated