> For the complete documentation index, see [llms.txt](https://captic-2.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://captic-2.gitbook.io/docs/overview/hands-on/integrating-your-robot/integration-flow/protocols/tcp.md).

# TCP

Connect to systems over raw TCP sockets.

Use the TCP nodes to talk to systems that expose a raw socket, such as a robot controller or a legacy system. You'll find them under **tcp** in the palette.

| Node        | What it does                                                                   |
| ----------- | ------------------------------------------------------------------------------ |
| tcp in      | Receives data, either by listening on a port or by connecting to a remote host |
| tcp out     | Sends data, either as a reply, to a connected client, or to a remote host      |
| tcp request | Sends a request to a remote host and outputs the reply                         |

A common pattern: run a pipeline with [Run Pipeline](/docs/overview/hands-on/integrating-your-robot/integration-flow.md), format the result as the string the other system expects, and send it with **tcp request**.

For node details, see the [Node-RED documentation](https://nodered.org/docs/user-guide/nodes).