Quite frequently, the connection between the debug client and xdebug breaks (debug clients tried: eclipse (Mars SR1), netbeans (8.1), sublime3). (It might be a connection reset due to php timeout, though that is set quite high.)

Unfortunately very often, xdebug subsequently enters into a frenzy of trying to connect back to the client. In the xampp-control window, one can see the apache process counting rapidly through ports. Looking at ProcessHacker, it's at least 10 connection attempts (= ports) per second.
The churning is so consuming that xdebug manages to make the whole Windows network stack throw up because it runs out of ports (error WSAENOBUFS blocks any further attempt open any kind of connection until apache is stopped, resulting in major disturbance for everything network-related, including the local mysql<->apache connection).

The problem is worsened by the fact that even restarting Apache can keep xdebug churning through connection attempts if the browser tries to access the afflicted site, even if clearing all cookies before trying so.

1. The error message in the log should include the concrete error returned by the stack:
   xdebug_create_socket should return the actual error code, xdebug_init_debugger log it (at least numerically)

2. xdebug should honor return codes of failed connections:
   On errors which are indicating a persistent failure - like connection refused -, xdebug_do_jit should stop trying to connect back (for a configurable hold-off period).

3. A way to reset xdebug would be very helpful. It seems to keep some (corrupted?) state information somewhere between apache restarts, any instruction how to clear that would make this a lot less painful.