Connect RPI with Bangle and send data

Hmm - when you get Software caused connection abort did you try it more than once just in case it was a glitch?

And how big is the JSON you're sending? Maybe it's huge and that causes a problem? You could just try something really basic.

command = "Y('+json.dumps(dict)+')\n"

Yes, that's what you'd expect - because as above you're sending the actual text, but not dict at all.

Maybe you could post up your complete code for us to take a look at?