socket.setTimeout() is an idle timeout in Node.js (node docs)[https://nodejs.org/api/net.html#socketsettimeouttimeout-callback]
- it fires after N ms of inactivity, not N ms after the connection attempt. This
caused false timeout errors after successful data transfers when connections
went idle for longer than the timeout period.
Replace with JS setTimeout() that:
- Fires N ms after connection attempt starts
- Gets cleared on successful connect
- Return 504 Gateway Timeout (more accurate than 502)
Also adds proper close event handlers for socket cleanup.
Fixes#228
