mage node.js api eka post man eken test karama hodata weda get, post , put request okkoma check kra. mongoose ekka ynne . post eken data idan insert wenawa kisi aulak nethuva postman eken test karaddi. but flutter android app ekaen api eka haraha data send kranna hedhuvama 500 internal error ekak enavane. fix kranne komada meka ?

http.dart file

import 'dart:convert';
import 'package:http/http.dart' as http;

class RequestResult
{
  bool ok;
  dynamic data;
  RequestResult(this.ok, this.data);
}

const PROTOCOL = 'http';
const DOMAIN = "192.168.*.**:3000";
//const ROUTE = "users/signup";
Future<RequestResult> http_post(String route, [dynamic data]) async
{
  var url = "$PROTOCOL://$DOMAIN/$route";
  var dataStr = jsonEncode(data);
  var result = await http.post(url, body: dataStr, headers:{"Content_Type": "application/json"});
  return RequestResult(true, jsonDecode(result.body));
}

signup.dart file

class _SignUpState extends State<SignUp> {

TextEditingController userNameController = TextEditingController();
TextEditingController emailController = TextEditingController();
TextEditingController phoneNumberController = TextEditingController();
TextEditingController nicController = TextEditingController();
TextEditingController passwordController = TextEditingController();
String response = "";

createUser() async {
  var result = await http_post("users/signup", {
    "userName": userNameController.text,
    "email": emailController.text,
    "phoneNumber": phoneNumberController.text,
    "nic": nicController.text,
    "password": passwordController.text,
  });
  if(result.ok)
  {
    setState(() {
      response = result.data['status'];
    });
  }
}

Api app.js code headers middlewaes

mongoose.Promise = global.Promise;
//middlewares
app.use(morgan('dev'));
app.use(bodyParser.urlencoded({extended: false}));
app.use(bodyParser.json());


//set access to all  connect to this api
 app.use((req, res, next) => {
    res.header('Access-Control-Allow-Origin', '*');
    res.header('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
    res.header('Access-Control-Allow-Headers', 'X-Requested-With, Origin, Content-Type, Accept, Authorization');
    next();
    
});

app.use('/users', usersRoutes);
app.use('/posts', postsRoutes);


app.use((req, res, next) =>{
    const error = new error('Not found');
    error.status= 404;
    next(error);
})

app.use((error, req, res, next) => {
    res.status(error.status || 500);
    res.json({
        error: {
            message: error.message
        }
    });
});
module.exports = app;