Feature: HTTP and WebSocket data source support

[SJ7F]

Summary

Adds support for WebSocket and streaming HTTP servers as a data source. Uses the same data format as the serial connection.

Motivation & Context

Implements the suggestion in #10 as close as possible (requires HTTP headers to be added to the beginning of the TCP stream)

Changes

• Added new HTTP/WS tab to connect modal
• Added useHttp.ts which does pretty much exactly what useSerial.ts does but with HTTP and WebSockets instead of Serial

How to Test

To test HTTP functionality:

1. Run the following python test code
2. Connect to http://localhost:8080 in the HTTP/WS Stream tab
3. Observe two sine waves being plotted

import asyncio
import math
import time

FREQ = 100  # messages per second
DT = 1 / FREQ
AMPLITUDE = 1.0
FREQ1 = 1.0  # Hz for first sine wave
FREQ2 = 0.5  # Hz for second sine wave

async def send_sine(reader, writer):
    t = 0.0
    
    try:
        writer.write(b"HTTP/1.1 200 OK\r\n")
        writer.write(b"Content-Type: text/plain; charset=utf-8\r\n")
        writer.write(b"Access-Control-Allow-Origin: *\r\n")
        writer.write(b"Cache-Control: no-cache\r\n")
        writer.write(b"Connection: keep-alive\r\n")
        writer.write(b"\r\n")
        while True:
            val1 = AMPLITUDE * math.sin(2 * math.pi * FREQ1 * t)
            val2 = AMPLITUDE * math.sin(2 * math.pi * FREQ2 * t)
            
            message = f"{val1},{val2}\n"
            writer.write(message.encode())
            await writer.drain()
            
            t += DT
            await asyncio.sleep(DT)
    except (asyncio.CancelledError, ConnectionResetError):
        print(f"client disconnected")
    finally:
        writer.close()
        await writer.wait_closed()

async def main():
    async with await asyncio.start_server(send_sine, "localhost", 8080) as server:
        addr = server.sockets[0].getsockname()
        print(f"TCP server running on {addr}")
        await server.serve_forever()

if __name__ == "__main__":
    asyncio.run(main())

To test WebSocket functionality:

1. Run the following python test code
2. Connect to ws://localhost:8080 in the HTTP/WS Stream tab
3. Observe two sine waves being plotted

import asyncio
import math
import websockets

FREQ = 100  # messages per second
DT = 1 / FREQ
AMPLITUDE = 1.0
FREQ1 = 1.0  # Hz for first sine wave
FREQ2 = 0.5  # Hz for second sine wave

async def send_sine(websocket, path):
    t = 0.0
    while True:
        val1 = AMPLITUDE * math.sin(2 * math.pi * FREQ1 * t)
        val2 = AMPLITUDE * math.sin(2 * math.pi * FREQ2 * t)
        
        await websocket.send(f"{val1},{val2}")
        
        t += DT
        await asyncio.sleep(DT)

async def main():
    async with websockets.serve(send_sine, "localhost", 8080):
        print("WebSocket server running on ws://localhost:8080")
        await asyncio.Future()  # run forever

if __name__ == "__main__":
    asyncio.run(main())

Checklist

• I ran npm run lint and fixed any issues
• I ran npm run typecheck (TypeScript) with no errors
• I ran npm test and tests pass
• I ran npm run test:coverage if code paths changed significantly
• I added/updated tests where appropriate
• I updated docs/README if needed
• No breaking changes without clear migration notes

Additional Notes

You cannot request resources served over an insecure protocol from a page served over HTTPS, and it is often impractical to set up TLS. @cgreening Perhaps a bundled single-file version of this web app could be provided to make it simpler for people to run locally?
I have duplicated a bit of text parsing code from useSerial.ts, it would probably be better to move that somewhere else and then call it from both useSerial.ts and useHttp.ts
I used Claude 3.5 Sonnet and GPT-5 to help write a portion of the code in this pull request.