lib/application: improve URL building algo

When running on Unix and no hostname is specified, use `0.0.0.0`
as the hostname instead of `localhost`.

When running on Windows and the hostname is either not specified or
it is `0.0.0.0` or `::`, use `localhost` in the URL. The reason is
that Windows cannot open URLs using `0.0.0.0` as a hostname.

lib/application.js

@@ -435,10 +435,24 @@ app.listen = function(cb) {
 
   server.on('listening', function() {
     self.set('port', this.address().port);
+
+    var listeningOnAll = false;
+    var host = self.get('host');
+    if (!host) {
+      listeningOnAll = true;
+      host = this.address().address;
+      self.set('host', host);
+    } else if (host === '0.0.0.0' || host === '::') {
+      listeningOnAll = true;
+    }
+
     if (!self.get('url')) {
-      // A better default host would be `0.0.0.0`,
-      // but such URL is not supported by Windows
-      var host = self.get('host') || '127.0.0.1';
+      if (process.platform === 'win32' && listeningOnAll) {
+        // Windows browsers don't support `0.0.0.0` host in the URL
+        // We are replacing it with localhost to build a URL
+        // that can be copied and pasted into the browser.
+        host = 'localhost';
+      }
       var url = 'http://' + host + ':' + self.get('port') + '/';
       self.set('url', url);
     }

test/app.test.js

@@ -213,8 +213,9 @@ describe('app', function() {
       app.set('host', undefined);
 
       app.listen(function() {
-        expect(app.get('url'), 'url')
-          .to.equal('http://127.0.0.1:' + app.get('port') + '/');
+        var host = process.platform === 'win32' ? 'localhost' : app.get('host');
+        var expectedUrl = 'http://' + host + ':' + app.get('port') + '/';
+        expect(app.get('url'), 'url').to.equal(expectedUrl);
         done();
       });
     });

test/remote-connector.test.js

@@ -12,7 +12,7 @@ describe('RemoteConnector', function() {
       remoteApp.use(loopback.rest());
       remoteApp.listen(0, function() {
         test.dataSource = loopback.createDataSource({
-          host: remoteApp.get('host'),
+          host: 'localhost',
           port: remoteApp.get('port'),
           connector: loopback.Remote
         });
@@ -38,7 +38,7 @@ describe('RemoteConnector', function() {
 
     remoteApp.listen(0, function() {
       test.remote = loopback.createDataSource({
-        host: remoteApp.get('host'),
+        host: 'localhost',
         port: remoteApp.get('port'),
         connector: loopback.Remote
       });
@@ -63,6 +63,7 @@ describe('RemoteConnector', function() {
 
     var m = new RemoteModel({foo: 'bar'});
     m.save(function(err, inst) {
+      if (err) return done(err);
       assert(inst instanceof RemoteModel);
       assert(calledServerCreate);
       done();