JSON WebSocket Sender @ vrch.ai

If the WebSocket Channel Loader is the pack's radio, this is the transmitter. The VrchJsonWebSocketSenderNode takes a JSON string and broadcasts it over a WebSocket channel to any listener connected to the same server - most commonly the matching loader node running on another machine. It's how a ComfyUI workflow on one box tells a ComfyUI instance (or browser, or custom script) on another what it's doing, live.

What it does

The inputs are the same trio the loader uses, plus the payload itself:

• server - the WebSocket server address as host:port. The default 172.17.0.2:8001 is a Docker bridge IP straight out of the developers' own container setup; you will almost certainly replace it with your own relay or endpoint. This is the single most common gotcha in the whole WebSocket set.
• channel - one of 8 numbered channels (1–8). Sender and receiver must agree on it, and it's your way of running multiple independent data streams over one server.
• json_string - the payload, typed in as multiline JSON. Defaults to {}.

It outputs JSON as a passthrough of what you sent, and it's an output node. That passthrough is handy for chaining: you can broadcast your payload and still have it flow onward in the graph without needing a reroute.

The debug toggle prints what's happening so you can confirm the send actually went out - worth switching on the first time, because a silent node that thinks it's sending when nobody's listening is a classic source of confusion.

Why you'd reach for it

This is the "talk to another machine" node. Pair it with the JSON WebSocket Channel Loader on a second instance and you've got a simple message bus between two ComfyUI boxes - send a prompt change, a status flag, or live control values and have the other side react in real time. It's the same pattern the pack uses for its real-time gamepad and control tutorials, just for JSON instead of pixels or latents. If you're not running anything multi-machine, this node does nothing for you on its own; it's the loaders and viewers that make it worth having.

Installing and fixing it

Shared pack install: clone VrchStudio/comfyui-web-viewer into ComfyUI/custom_nodes, pip install -r comfyui-web-viewer/requirements.txt, restart - or just search ComfyUI Web Viewer in Manager. No model files involved.

When a receiver stays silent: check the server address first, then the channel on both ends, then flip debug on the sender and confirm the message left. A typo in json_string (invalid JSON) is the other classic failure - the sender can't serialize what you typed.