> ## Documentation Index
> Fetch the complete documentation index at: https://docs.comfy.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Server Overview

## Overview

The Comfy server runs on top of the [aiohttp framework](https://docs.aiohttp.org/), which in turn uses [asyncio](https://pypi.org/project/asyncio/).

Messages from the server to the client are sent by socket messages through the `send_sync` method of the server,
which is an instance of `PromptServer` (defined in `server.py`). They are processed
by a socket event listener registered in `api.js`. See [messages](/development/comfyui-server/comms_messages).

Messages from the client to the server are sent by the `api.fetchApi()` method defined in `api.js`,
and are handled by http routes defined by the server. See [routes](/development/comfyui-server/comms_routes).

<Tip>The client submits the whole workflow (widget values and all) when you queue a request.
The server does not receive any changes you make after you send a request to the queue.
If you want to modify server behavior during execution, you'll need routes.</Tip>