# TCP

The **tcp** input plugin allows to retrieve structured JSON or raw messages over a TCP network interface (TCP port).

## Configuration Parameters

The plugin supports the following configuration parameters:

| Key          | Description                                                                                                                                                                                                                                                    | Default |
| ------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------- |
| Listen       | Listener network interface.                                                                                                                                                                                                                                    | 0.0.0.0 |
| Port         | TCP port where listening for connections                                                                                                                                                                                                                       | 5170    |
| Buffer\_Size | Specify the maximum buffer size in KB to receive a JSON message. If not set, the default size will be the value of *Chunk\_Size*.                                                                                                                              |         |
| Chunk\_Size  | By default the buffer to store the incoming JSON messages, do not allocate the maximum memory allowed, instead it allocate memory when is required. The rounds of allocations are set by *Chunk\_Size* in KB. If not set, *Chunk\_Size* is equal to 32 (32KB). | 32      |
| Format       | Specify the expected payload format. It support the options *json* and *none*. When using *json*, it expects JSON maps, when is set to *none*, it will split every record using the defined *Separator* (option below).                                        | json    |
| Separator    | When the expected *Format* is set to *none*, Fluent Bit needs a separator string to split the records. By default it uses the breakline character (LF or 0x10).                                                                                                |         |

## Getting Started

In order to receive JSON messages over TCP, you can run the plugin from the command line or through the configuration file:

### Command Line

From the command line you can let Fluent Bit listen for *JSON* messages with the following options:

```bash
$ fluent-bit -i tcp -o stdout
```

By default the service will listen an all interfaces (0.0.0.0) through TCP port 5170, optionally you can change this directly, e.g:

```bash
$ fluent-bit -i tcp://192.168.3.2:9090 -o stdout
```

In the example the JSON messages will only arrive through network interface under 192.168.3.2 address and TCP Port 9090.

### Configuration File

In your main configuration file append the following *Input* & *Output* sections:

```python
[INPUT]
    Name        tcp
    Listen      0.0.0.0
    Port        5170
    Chunk_Size  32
    Buffer_Size 64
    Format      json

[OUTPUT]
    Name        stdout
    Match       *
```

## Testing

Once Fluent Bit is running, you can send some messages using the *netcat*:

```bash
$ echo '{"key 1": 123456789, "key 2": "abcdefg"}' | nc 127.0.0.1 5170
```

In [Fluent Bit](http://fluentbit.io) we should see the following output:

```bash
$ bin/fluent-bit -i tcp -o stdout -f 1
Fluent Bit v1.x.x
* Copyright (C) 2019-2020 The Fluent Bit Authors
* Copyright (C) 2015-2018 Treasure Data
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

[2019/10/03 09:19:34] [ info] [storage] initializing...
[2019/10/03 09:19:34] [ info] [storage] in-memory
[2019/10/03 09:19:34] [ info] [engine] started (pid=14569)
[2019/10/03 09:19:34] [ info] [in_tcp] binding 0.0.0.0:5170
[2019/10/03 09:19:34] [ info] [sp] stream processor started
[0] tcp.0: [1570115975.581246030, {"key 1"=>123456789, "key 2"=>"abcdefg"}]
```

## Performance Considerations

When receiving payloads in JSON format, there are high performance penalties. Parsing JSON is a very expensive task so you could expect your CPU usage increase under high load environments.

To get faster data ingestion, consider to use the option `Format none` to avoid JSON parsing if not needed.