Easy Things that are Hard

Something that should be easy but weirdly isn’t is sharing text or files between two of my devices, say a laptop and a phone. There are lots of sometime solutions for this - if you have a Macbook and an iPhone on the same account, you have a shared clipboard, and KDE Connect is also designed to solve this, but unfortunately its support for macOS is experimental and doesn’t seem to support Apple Silicon. Failing that, there are the more prosaic workarounds: texting it to a trusted friend (and maybe deleting afterwards), or emailing it to yourself. These solutions are inelegant to me - why should I send a file all the way to a Google or WhatsApp or Dropbox server just to move it 20 centimetres physically, within the same local network? There must be a better way!

(My previous solutions have also included using my knowledge base Joplin, which also roundtrips to Dropbox [side point: another rainy day project is to use local sync most of the time for this, with a separate regular backup to Dropbox, but this does at least pose more difficult problems of consistency and resolving conflicts, etc], or else using the unpretentious https://sharetxt.live, built for this purpose, but sharing everything publicly unless you log in.)

Anyway, I’ve recently been writing long messages to send on my phone, so I want to edit them in Emacs and then send them to my phone clipboard. This is actually easy to solve with a local server (so the title of this post is wrong I guess…), and I’m mainly just putting it here to remember the exact command. I use buffer.txt for editing, then in app.py I have:

from flask import Flask

app = Flask(__name__)

@app.route("/")
def message():
    with open('buffer.txt') as f:
        return f"<p>{'<br>'.join(f.readlines())}</p>"

And then launch with flask --debug run --host=0.0.0.0 --port=5001. Explanations for the options:

• debug is to auto-reload the server whenever one of the files in the directory changes (in this case buffer.txt)
• host given explicitly is to make it available to other machines on the network, which is otherwise disabled as a security precaution. Python’s http.server doesn’t restrict this, but it only allows files to be viewed and downloaded, not code execution.
• Explicit port is only needed because the default, 5000, is used by Apple for some dumb service of its own (AirPlay Receiver, whatever that is).

Then the text is accessible to any device connected to the local network at http://<internal IP address>:5001.