Problem Description: I'm working on a full-stack application using React (frontend), Express.js (backend), and MongoDB. While trying to send a POST request from my React frontend to the Express backend, I encounter the following error: ERR_CONNECTION_REFUSED.

The error i get

//Register.jsx (Frontend)
import React, {Component, useState } from 'react'
import styled from "styled-components"
import {Link} from "react-router-dom"
import  "../css/register.css"
import axios from "axios";

const Register = () => {

  const [username,setUserName] = useState("");
  const [email,setEmail] = useState("");
  const [password,setPassword] = useState("");
  const [passwordagain,setPasswordAgain] = useState("");
  const [errorMessage, setErrorMessage] = useState("");


  const handleSubmit = async (event) => {
    event.preventDefault();
  
    if (password === passwordagain) {
      const userData = { username, email, password };
      console.log("We want post:", userData);  
  
      try {
        const response = await fetch('http://localhost:5000/auth/register', {
          method: 'POST',
          headers: {
            'Content-Type': 'application/json',
          },
          body: JSON.stringify(userData),
        });
        
  
        const data = await response.json(); // JSON Data
        if (response.ok) {
          console.log("Register Success:", data);
        } else {
          console.log("Register Unsuccesfull:", data);
          setErrorMessage("Please Try Again.");
        }
      } catch (error) {
        console.error("Error:", error.message);
        setErrorMessage("Register Unsuccesfull,Please Try Again.");
      }
    } else {
      setErrorMessage("passwords do not match");
    }
  };


  return (
    <div>
      <div className="formcontainer">
      <form className="form" onSubmit={(event)=>(handleSubmit(event))}>
          <input
            type="text"
            value={username}
            placeholder="Enter your username"
            name="username"
            className="input"
            onChange={(e) => setUserName(e.target.value)}
          />
          <input
            type="email"
            value={email}
            placeholder="Enter your email"
            name="email"
            className="input"
            onChange={(e) => setEmail(e.target.value)}
          />
          <input
            type="password"
            value={password}
            placeholder="Enter password"
            name="password"
            className="input"
            onChange={(e) => setPassword(e.target.value)}
          />
          <input
            type="password"
            value={passwordagain}
            placeholder="Enter password again"
            name="passwordagain"
            className="input"
            onChange={(e) => setPasswordAgain(e.target.value)}
          />
          <button type="submit">Register</button>
        </form>
        {errorMessage && <p style={{ color: "red" }}>{errorMessage}</p>}

      </div>


    </div>
  )
}

export default Register

//index.js

const express = require("express");
const cors = require("cors");
const mongoose = require("mongoose");
const dotenv = require("dotenv");
const authRoutes = require("./routes/authRoutes");
dotenv.config();

const app = express();

// Middleware
app.use(cors({
  origin: "http://localhost:3000", // Frontend
  methods: "GET,POST,PUT,DELETE",
  credentials: true,
}));
app.use(express.json()); // JSON 
app.use(express.urlencoded({ extended: true })); // URL-encoded 

mongoose.connect(process.env.MONGO_URI, {
  useNewUrlParser: true,
  useUnifiedTopology: true,
})
  .then(() => console.log("MongoDB Connected."))
  .catch(err => console.log("MongoDB Connection Error:", err));

app.use("/auth", authRoutes);

const PORT = 5000;
app.listen(PORT, () => {
  console.log(`Server is running. Port: ${PORT}`);
});

//authRoutes.js

const express = require("express");
const router = express.Router();

const authPost = require("../controllers/authControllers");

router.post("/register", authPost);

module.exports = router;

//authController.js

// authController.js
const Auth = require("../models/authModel"); // Import Model

const authPost = async (req, res) => {
  const { username, email, password } = req.body;
  console.log("Request Data In Server:", req.body); // Logging Request

  const newUser = new Auth({
    username,
    email,
    password,
  });

  try {
    // Kullanıcıyı veritabanına kaydediyoruz
    const savedUser = await newUser.save();
    console.log("Yeni kullanıcı kaydedildi:", savedUser);  // Detailed log
    res.status(201).send("Kayıt başarılı");
  } catch (error) {
    console.error("Veritabanı hatası:", error);  // Error Message
    res.status(500).send("Kayıt başarısız: " + error.message);
  }
};
module.exports = authPost;

//authModel.js
const mongoose= require("mongoose");


 const authSchema = mongoose.Schema({
    username: { type: String, required: true },
  email: { type: String, required: true },
  password: { type: String, required: true }

});


const Auth = mongoose.model("Auth", authSchema); // Collection name 'User'

I've already tried the following steps:

I checked my routes and used Postman to verify it. Verified that the backend is running on http://localhost:5000. Added the cors middleware to the backend. Checked the fetch request configuration in the frontend. However, the issue persists, and the backend doesn't seem to receive the request.

Problem Description: I'm working on a full-stack application using React (frontend), Express.js (backend), and MongoDB. While trying to send a POST request from my React frontend to the Express backend, I encounter the following error: ERR_CONNECTION_REFUSED.

The error i get

//Register.jsx (Frontend)
import React, {Component, useState } from 'react'
import styled from "styled-components"
import {Link} from "react-router-dom"
import  "../css/register.css"
import axios from "axios";

const Register = () => {

  const [username,setUserName] = useState("");
  const [email,setEmail] = useState("");
  const [password,setPassword] = useState("");
  const [passwordagain,setPasswordAgain] = useState("");
  const [errorMessage, setErrorMessage] = useState("");


  const handleSubmit = async (event) => {
    event.preventDefault();
  
    if (password === passwordagain) {
      const userData = { username, email, password };
      console.log("We want post:", userData);  
  
      try {
        const response = await fetch('http://localhost:5000/auth/register', {
          method: 'POST',
          headers: {
            'Content-Type': 'application/json',
          },
          body: JSON.stringify(userData),
        });
        
  
        const data = await response.json(); // JSON Data
        if (response.ok) {
          console.log("Register Success:", data);
        } else {
          console.log("Register Unsuccesfull:", data);
          setErrorMessage("Please Try Again.");
        }
      } catch (error) {
        console.error("Error:", error.message);
        setErrorMessage("Register Unsuccesfull,Please Try Again.");
      }
    } else {
      setErrorMessage("passwords do not match");
    }
  };


  return (
    <div>
      <div className="formcontainer">
      <form className="form" onSubmit={(event)=>(handleSubmit(event))}>
          <input
            type="text"
            value={username}
            placeholder="Enter your username"
            name="username"
            className="input"
            onChange={(e) => setUserName(e.target.value)}
          />
          <input
            type="email"
            value={email}
            placeholder="Enter your email"
            name="email"
            className="input"
            onChange={(e) => setEmail(e.target.value)}
          />
          <input
            type="password"
            value={password}
            placeholder="Enter password"
            name="password"
            className="input"
            onChange={(e) => setPassword(e.target.value)}
          />
          <input
            type="password"
            value={passwordagain}
            placeholder="Enter password again"
            name="passwordagain"
            className="input"
            onChange={(e) => setPasswordAgain(e.target.value)}
          />
          <button type="submit">Register</button>
        </form>
        {errorMessage && <p style={{ color: "red" }}>{errorMessage}</p>}

      </div>


    </div>
  )
}

export default Register

//index.js

const express = require("express");
const cors = require("cors");
const mongoose = require("mongoose");
const dotenv = require("dotenv");
const authRoutes = require("./routes/authRoutes");
dotenv.config();

const app = express();

// Middleware
app.use(cors({
  origin: "http://localhost:3000", // Frontend
  methods: "GET,POST,PUT,DELETE",
  credentials: true,
}));
app.use(express.json()); // JSON 
app.use(express.urlencoded({ extended: true })); // URL-encoded 

mongoose.connect(process.env.MONGO_URI, {
  useNewUrlParser: true,
  useUnifiedTopology: true,
})
  .then(() => console.log("MongoDB Connected."))
  .catch(err => console.log("MongoDB Connection Error:", err));

app.use("/auth", authRoutes);

const PORT = 5000;
app.listen(PORT, () => {
  console.log(`Server is running. Port: ${PORT}`);
});

//authRoutes.js

const express = require("express");
const router = express.Router();

const authPost = require("../controllers/authControllers");

router.post("/register", authPost);

module.exports = router;

//authController.js

// authController.js
const Auth = require("../models/authModel"); // Import Model

const authPost = async (req, res) => {
  const { username, email, password } = req.body;
  console.log("Request Data In Server:", req.body); // Logging Request

  const newUser = new Auth({
    username,
    email,
    password,
  });

  try {
    // Kullanıcıyı veritabanına kaydediyoruz
    const savedUser = await newUser.save();
    console.log("Yeni kullanıcı kaydedildi:", savedUser);  // Detailed log
    res.status(201).send("Kayıt başarılı");
  } catch (error) {
    console.error("Veritabanı hatası:", error);  // Error Message
    res.status(500).send("Kayıt başarısız: " + error.message);
  }
};
module.exports = authPost;

//authModel.js
const mongoose= require("mongoose");


 const authSchema = mongoose.Schema({
    username: { type: String, required: true },
  email: { type: String, required: true },
  password: { type: String, required: true }

});


const Auth = mongoose.model("Auth", authSchema); // Collection name 'User'

I've already tried the following steps:

I checked my routes and used Postman to verify it. Verified that the backend is running on http://localhost:5000. Added the cors middleware to the backend. Checked the fetch request configuration in the frontend. However, the issue persists, and the backend doesn't seem to receive the request.

• reactjs
• node.js
• mongodb
• mern

1 Answer 1

• In index.js dotenv.config() should be used
• Go to your MongoDB network access and change it to access from everywhere.
• Clear browser cache
• Check your API keys

If error still occurred use your local MONGODB