Updated HttpServer documentation to specify that only IPv6 connections can be made when specifying …

tests/standalone/io/http_loopback_test.dart

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "dart:io";
+import "package:expect/expect.dart";
+
+RawServerSocket server;
+RawSocket client;
+
+serverListen(RawSocket serverSide) {
+  serveData(RawSocketEvent event) {
+    serverSide.shutdown(SocketDirection.SEND);
+  }
+
+  serverSide.listen(serveData);
+}
+
+IPv4ToIPv6FailureTest() async {
+  server = await RawServerSocket.bind(InternetAddress.LOOPBACK_IP_V6, 0);
+  server.listen(serverListen);
+  bool testFailure = false;
+  try {
+    client =
+        await RawSocket.connect(InternetAddress.LOOPBACK_IP_V4, server.port);
+    await client.close();
+    testFailure = true;
+  } on SocketException catch (e) {
+    // We shouldn't be able to connect to the IPv6 loopback adapter using the
+    // IPv4 loopback address.
+  } catch (e) {
+    testFailure = true;
+  } finally {
+    Expect.equals(testFailure, false);
+    await server.close();
+  }
+}
+
+IPv6ToIPv4FailureTest() async {
+  server = await RawServerSocket.bind(InternetAddress.LOOPBACK_IP_V4, 0);
+  server.listen(serverListen);
+  bool testFailure = false;
+  try {
+    client =
+        await RawSocket.connect(InternetAddress.LOOPBACK_IP_V6, server.port);
+    await client.close();
+    testFailure = true;
+  } on SocketException catch (e) {
+    // We shouldn't be able to connect to the IPv4 loopback adapter using the
+    // IPv6 loopback address.
+  } catch (e) {
+    testFailure = true;
+  } finally {
+    Expect.equals(testFailure, false);
+    await server.close();
+  }
+}
+
+loopbackSuccessTest(InternetAddress address) async {
+  server = await RawServerSocket.bind(address, 0);
+  server.listen(serverListen);
+  bool testFailure = false;
+  try {
+    client = await RawSocket.connect(address, server.port);
+    await client.close();
+  } catch (e) {
+    testFailure = true;
+  } finally {
+    Expect.equals(testFailure, false);
+    await server.close();
+  }
+}
+
+main() async {
+  await IPv4ToIPv6FailureTest();
+  await IPv6ToIPv4FailureTest();
+  await loopbackSuccessTest(InternetAddress.LOOPBACK_IP_V4);
+  await loopbackSuccessTest(InternetAddress.LOOPBACK_IP_V6);
+}