net: track and close connections in a pre-exit hook

This is an attempt to fix the flaky failures on http(s) and
tcp tests on Windows.

Signed-off-by: James M Snell <jasnell@gmail.com>
Assisted-by: Opencode/Opus 4.6

Author: jasnell

lib/net.js

@@ -35,6 +35,7 @@ const {
   NumberParseInt,
   ObjectDefineProperty,
   ObjectSetPrototypeOf,
+  SafeSet,
   Symbol,
   SymbolAsyncDispose,
   SymbolDispose,
@@ -912,6 +913,7 @@ Socket.prototype._destroy = function(exception, cb) {
   if (this._server) {
     debug('has server');
     this._server._connections--;
+    this._server._connectionSockets?.delete(this);
     if (this._server._emitCloseIfDrained) {
       this._server._emitCloseIfDrained();
     }
@@ -1867,6 +1869,7 @@ function Server(options, connectionListener) {
   }
 
   this._connections = 0;
+  this._connectionSockets = new SafeSet();
 
   this[async_id_symbol] = -1;
   this._handle = null;
@@ -2365,6 +2368,7 @@ function onconnection(err, clientHandle) {
   }
 
   self._connections++;
+  self._connectionSockets.add(socket);
   socket.server = self;
   socket._server = self;
   self.emit('connection', socket);
@@ -2436,6 +2440,22 @@ Server.prototype.close = function(cb) {
     this._handle = null;
   }
 
+  // Register a beforeExit handler to destroy any remaining connections
+  // before the process exits. This ensures connections are torn down
+  // during normal JS execution rather than during environment cleanup,
+  // where on Windows the IOCP completion processing can race with
+  // handle teardown.
+  if (this._connectionSockets.size > 0) {
+    const connections = this._connectionSockets;
+    const onBeforeExit = () => {
+      process.removeListener('beforeExit', onBeforeExit);
+      for (const socket of connections) {
+        socket.destroy();
+      }
+    };
+    process.on('beforeExit', onBeforeExit);
+  }
+
   if (this._usingWorkers) {
     let left = this._workers.length;
     const onWorkerClose = () => {