[ DDS ] Prefer IPv6 addresses if the VM service is using IPv6

Fixes #56557

Change-Id: I6c18f31a49e6e0d924a467b4b8c1f9d5709d47d8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/382020
Commit-Queue: Derek Xu <[email protected]>
Commit-Queue: Ben Konyi <[email protected]>
Reviewed-by: Derek Xu <[email protected]>
Auto-Submit: Ben Konyi <[email protected]>

pkg/dds/lib/src/dds_cli_entrypoint.dart

@@ -55,16 +55,21 @@ ${argParser.usage}
     argResults[DartDevelopmentServiceOptions.vmServiceUriOption],
   );
 
+  // Prefer IPv4 addresses if we can't determine the address type from the
+  // VM service host.
+  final preferredProtocolType =
+      InternetAddress.tryParse(remoteVmServiceUri.host)?.type ??
+          InternetAddressType.IPv4;
+
   // Resolve the address which is potentially provided by the user.
   late InternetAddress address;
   final bindAddress =
       argResults[DartDevelopmentServiceOptions.bindAddressOption];
   try {
     final addresses = await InternetAddress.lookup(bindAddress);
-    // Prefer IPv4 addresses.
     for (int i = 0; i < addresses.length; i++) {
       address = addresses[i];
-      if (address.type == InternetAddressType.IPv4) break;
+      if (address.type == preferredProtocolType) break;
     }
   } on SocketException catch (e, st) {
     writeErrorResponse('Invalid bind address: $bindAddress', st);