Langchain websocket server example with TypeScript and Ollama

This is a simple websocket server that uses LangChain and Ollama to provide a chat interface.

Run Demo

Uses Node.js v22.6.0 or later.

Install Ollama or use another LLM compatible with LangChain. Run ollama run llama3.1 to start the Ollama server.

npm install
npm start

In a separate terminal, run the test to see the completion response:

npm test

How to create a new websocket client to connect to the server.

Examples were generated with an LLM and were not tested.

Vanilla example:

const ws = new WebSocket("ws://localhost:8080");

ws.on("open", () => {
  console.log("Connected to the server");
});

ws.on("message", (data) => {
  console.log("Received message:", data);
});

ws.on("close", () => {
  console.log("Disconnected from the server");
});

ws.send("Hello");

Example with React:

import { useEffect, useState } from "react";

const App = () => {
  const [messages, setMessages] = useState<string[]>([]);
  const [input, setInput] = useState<string>("");

  useEffect(() => {
    const ws = new WebSocket('ws://localhost:3000');

    ws.onopen = () => {
      console.log('WebSocket connection established.');
    };

    ws.onmessage = (event) => {
      setMessages((prevMessages) => [...prevMessages, event.data]);
    };

    return () => {
      ws.close();
    };
  }, []);

  return (
    <div>
      <h1>WebSocket Chat</h1>
      <div>
        {messages.map((message, index) => (
          <p key={index}>{message}</p>
        ))}
      </div>
      <div>
        <input type="text" value={input} onChange={(e) => setInput(e.target.value)} />
        <button onClick={sendMessage}>Send</button>
      </div>
    </div>
  );
};

export default App;