Trying to harden client.getUrl() in Dart, so it never crashes my HTTP server and never completes with an error.

gistfile1.dart

Future getTag() {
    final Completer  c      = new Completer();
    final HttpClient client = new HttpClient();

    client.getUrl(Uri.parse(tagUrl))
      .then((HttpClientRequest request) {
        return request.close();
      })
      .catchError((e) {
        // If the tagUrl server is down, we catch and log it here.
        log('MetaData.getTag() -> client.getUrl() failed to establish connection ${e}');
      })
      .then((HttpClientResponse response) {
        // It seems this null check is necessary, in case the connection failed. If I don't
        // check for null, I end up trying to access stuff in the null response object.
        if(response != null) {
          switch(response.statusCode) {
            case 200:
              log('MetaData.getTag() -> client.getUrl() ${tagUrl} fetched OK');
              response.listen((value) {
                try {
                  tag = LATIN1.decode(value).trim();
                } catch(e) {
                  // I feel I must catch decoding errors here, but it seems somewhat excessive
                  // with a "massive" try-catch block.  
                  log('${e} - ${this}');
                  tag = null;
                }
              }, onError: (e) {
                // Catch stream errors and drain the response. I've no idea what would trigger
                // this, but better safe than sorry I guess.
                response.drain();
                log('${e} - ${this}');
              });
              break;
            default:
              response.drain();
              log('MetaData.getTag() -> client.getUrl() failed with status code ${response.statusCode} - ${this}');
          }
        }
      })
      .catchError((e) {
        log('${e} - ${this}');
      })
      .whenComplete(() {
        // Complete with success, no matter what happened above.
        c.complete();
      });
   
    // This client.close() call seems to be OK , even if the connection fails. I'm not sure
    // where else to put it. Is it even necessary?
    client.close();

    return c.future;
  }