better offline reconnect behavior

[feross]

When internet connectivity is lost, webtorrent (websocket) tracker connections are lost and no reconnect happens. We should detect this condition and improve how it's handled.

This module might help: https://github.com/feross/connectivity

[feross]

Reconnect behavior could still be improved. I don't see https://instant.io reconnecting to the websocket tracker after my laptop battery has died, or I've shut the lid.

[feross]

The socket's readyState is 1, which is WebSocket.OPEN. Maybe we need to send heartbeats or something? Why isn't the 'close' event firing?

[feross]

This is fixed now. You can go offline, come back online, and the download should resume. Also, remote peers who may be waiting for peers (because they have 0), will be able to connect to you.

There were many bugs that I squashed to close this issue:

simple-websocket

• emit 'close' event correctly when we go offline feross/simple-websocket@3ff3010

bittorrent-tracker

• announce on reconnect webtorrent/bittorrent-tracker@6ef2d98
• remove socket from pool on destroy webtorrent/bittorrent-tracker@4128604
• webtorrent/bittorrent-tracker@6ef2d98

This fix is live on https://instant.io, and in webtorrent if you run npm update.