net: use close callback, not process.nextTick

Don't emit the 'close' event with process.nextTick.

Closing a handle is an operation that usually *but not always* completes
on the next tick of the event loop, hence using process.nextTick is not
reliable.

Use a proper handle close callback and emit the 'close' event from
inside the callback.

Update tests that depend on the intricacies of the old model.

Fixes #3459.

lib/net.js

@@ -430,18 +430,16 @@ Socket.prototype._destroy = function(exception, cb) {
   if (this._handle) {
     if (this !== process.stderr)
       debug('close handle');
-    this._handle.close();
+    var isException = exception ? true : false;
+    this._handle.close(function() {
+      debug('emit close');
+      self.emit('close', isException);
+    });
     this._handle.onread = noop;
     this._handle = null;
   }
 
   fireErrorCallbacks();
-
-  process.nextTick(function() {
-    debug('emit close');
-    self.emit('close', exception ? true : false);
-  });
-
   this.destroyed = true;
 
   if (this.server) {

test/simple/test-http-agent-destroyed-socket.js

@@ -65,7 +65,7 @@ var request1 = http.get(requestOptions, function(response) {
     // is triggered.
     request1.socket.destroy();
 
-    process.nextTick(function() {
+    response.once('close', function() {
       // assert request2 was removed from the queue
       assert(!agent.requests[key]);
       console.log("waiting for request2.onSocket's nextTick");

test/simple/test-net-server-close.js

@@ -28,7 +28,11 @@ var sockets = [];
 
 process.on('exit', function() {
   assert.equal(server.connections, 0);
-  assert.deepEqual(events, 'client client server'.split(' '));
+  assert.equal(events.length, 3);
+  // Expect to see one server event and two client events. The order of the
+  // events is undefined because they arrive on the same event loop tick.
+  assert.equal(events.join(' ').match(/server/g).length, 1);
+  assert.equal(events.join(' ').match(/client/g).length, 2);
 });
 
 var server = net.createServer(function(c) {

test/simple/test-process-active-wraps.js

@@ -29,12 +29,15 @@ function expect(activeHandles, activeRequests) {
   assert.equal(process._getActiveRequests().length, activeRequests);
 }
 
+var handles = [];
+
 (function() {
   expect(0, 0);
   var server = net.createServer().listen(common.PORT);
   expect(1, 0);
   server.close();
   expect(1, 0); // server handle doesn't shut down until next tick
+  handles.push(server);
 })();
 
 (function() {
@@ -44,18 +47,15 @@ function expect(activeHandles, activeRequests) {
   expect(2, 1);
   conn.destroy();
   expect(2, 1); // client handle doesn't shut down until next tick
+  handles.push(conn);
 })();
 
-// Force the nextTicks to be deferred to a later time.
-process.maxTickDepth = 1;
-
-process.nextTick(function() {
-  process.nextTick(function() {
-    process.nextTick(function() {
-      process.nextTick(function() {
-        // the handles should be gone but the connect req could still be alive
-        assert.equal(process._getActiveHandles().length, 0);
-      });
-    });
-  });
+(function() {
+  var n = 0;
+  handles.forEach(function(handle) {
+    handle.once('close', onclose);
   });
+  function onclose() {
+    if (++n === handles.length) setImmediate(expect, 0, 0);
+  }
+})();