dgram: default send address to 127.0.0.1 or ::1

In net we default to 'localhost' as the default address for connect.
Not doing the same on dgram is confusing, because sending to 0.0.0.0
works on Linux/OS X but not on Windows. Defaulting that to 127.0.0.1 /
::1 addresses that.

Related: #5407
Related: #5398
Fixes: #5487
PR-URL: #5493
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>

doc/api/dgram.markdown

@@ -209,10 +209,7 @@ If `msg` is an array, `offset` and `length` must not be specified.
 
 The `address` argument is a string. If the value of `address` is a host name,
 DNS will be used to resolve the address of the host. If the `address` is not
-specified or is an empty string, `'0.0.0.0'` or `'::0'` will be used instead.
-It is possible, depending on the network configuration, that these defaults
-may not work; accordingly, it is best to be explicit about the destination
-address.
+specified or is an empty string, `'127.0.0.1'` or `'::1'` will be used instead.
 
 If the socket has not been previously bound with a call to `bind`, the socket
 is assigned a random port number and is bound to the "all interfaces" address

lib/dgram.js

@@ -29,12 +29,12 @@ function lookup(address, family, callback) {
 
 
 function lookup4(address, callback) {
-  return lookup(address || '0.0.0.0', 4, callback);
+  return lookup(address || '127.0.0.1', 4, callback);
 }
 
 
 function lookup6(address, callback) {
-  return lookup(address || '::0', 6, callback);
+  return lookup(address || '::1', 6, callback);
 }
 
 
@@ -166,6 +166,13 @@ Socket.prototype.bind = function(port_ /*, address, callback*/) {
     exclusive = false;
   }
 
+  // defaulting address for bind to all interfaces
+  if (!address && self._handle.lookup === lookup4) {
+    address = '0.0.0.0';
+  } else if (!address && self._handle.lookup === lookup6) {
+    address = '::';
+  }
+
   // resolve address first
   self._handle.lookup(address, function(err, ip) {
     if (err) {

test/parallel/test-dgram-send-default-host.js

@@ -4,19 +4,8 @@ const common = require('../common');
 const assert = require('assert');
 const dgram = require('dgram');
 
-if (common.isWindows) {
-  // on Windows this test will fail
-  // see https://github.com/nodejs/node/pull/5407
-  console.log('1..0 # Skipped: This test does not apply on Windows.');
-  return;
-}
-
 const client = dgram.createSocket('udp4');
 
-const timer = setTimeout(function() {
-  throw new Error('Timeout');
-}, common.platformTimeout(2000));
-
 const toSend = [new Buffer(256), new Buffer(256), new Buffer(256), 'hello'];
 
 toSend[0].fill('x');
@@ -36,7 +25,6 @@ client.on('message', function(buf, info) {
 
   if (toSend.length === 0) {
     client.close();
-    clearTimeout(timer);
   }
 });
 

test/parallel/test-dgram-udp6-send-default-host.js

@@ -0,0 +1,36 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const dgram = require('dgram');
+
+if (!common.hasIPv6) {
+  console.log('1..0 # Skipped: no IPv6 support');
+  return;
+}
+
+const client = dgram.createSocket('udp6');
+
+const toSend = [new Buffer(256), new Buffer(256), new Buffer(256), 'hello'];
+
+toSend[0].fill('x');
+toSend[1].fill('y');
+toSend[2].fill('z');
+
+client.on('listening', function() {
+  client.send(toSend[0], 0, toSend[0].length, common.PORT);
+  client.send(toSend[1], common.PORT);
+  client.send([toSend[2]], common.PORT);
+  client.send(toSend[3], 0, toSend[3].length, common.PORT);
+});
+
+client.on('message', function(buf, info) {
+  const expected = toSend.shift().toString();
+  assert.ok(buf.toString() === expected, 'message was received correctly');
+
+  if (toSend.length === 0) {
+    client.close();
+  }
+});
+
+client.bind(common.PORT);