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How to Fix Python ConnectionRefusedError

Resolve Python ConnectionRefusedError when network connections are rejected, covering server availability, port issues, and firewall configurations.

Published: Nov 27, 202510 min readBy FixWikiHub Editorial Team

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# How to Fix Python ConnectionRefusedError

The ConnectionRefusedError occurs when a network connection attempt is actively rejected by the remote host. This typically means the target server is not listening on the specified port, or a firewall is blocking the connection.

Introduction

This article covers troubleshooting steps and solutions for How to Fix Python ConnectionRefusedError. The error typically occurs in production environments and can cause service disruptions if not addressed promptly.

Symptoms

Basic ConnectionRefusedError

text

Traceback (most recent call last):
  File "app.py", line 5, in <module>
    socket.connect(('localhost', 8080))
ConnectionRefusedError: [Errno 111] Connection refused

HTTP Request Connection Refused

text

Traceback (most recent call last):
  File "app.py", line 10, in <module>
    requests.get('http://localhost:8080/api')
ConnectionRefusedError: [Errno 111] Connection refused

Database Connection Refused

text

Traceback (most recent call last):
  File "app.py", line 15, in <module>
    psycopg2.connect(host='localhost', port=5432)
ConnectionRefusedError: [Errno 111] Connection refused

WebSocket Connection Refused

text

Traceback (most recent call last):
  File "app.py", line 20, in <module>
    websocket.connect('ws://localhost:8080/ws')
ConnectionRefusedError: [Errno 111] Connection refused

Common Causes

1.Server not running - Target service is not started
2.Wrong port - Connecting to different port than server listens on
3.Wrong host - Server on different IP address
4.Firewall blocking - Network firewall rejecting connections
5.Service crashed - Server process crashed or stopped
6.Port not bound - Server not configured to listen on port
7.IPv4/IPv6 mismatch - Connecting with wrong protocol version
8.Local firewall - Host firewall blocking inbound connections

Step-by-Step Fix

Step 1: Check if Server is Running

```bash # Linux/Mac ps aux | grep nginx # Check process ps aux | grep python netstat -tlnp # Listening ports ss -tlnp # Alternative to netstat

# Windows tasklist | findstr python netstat -an # All connections ```

Step 2: Check Port is Listening

```bash # Check specific port netstat -tlnp | grep 8080 ss -tlnp | grep 8080 lsof -i :8080

# Or test with nc nc -zv localhost 8080 # Output: localhost 8080 open (if listening) # Output: localhost 8080 refused (if not) ```

Step 3: Check Firewall Rules

```bash # Linux (iptables) iptables -L -n

# Linux (firewalld) firewall-cmd --list-all

# Linux (ufw) ufw status

# Windows netsh advfirewall show allprofiles ```

Step 4: Test from Python

```python import socket

def test_connection(host, port): """Test if connection is possible.""" sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.settimeout(2)

try: result = sock.connect_ex((host, port)) if result == 0: print(f"Connection to {host}:{port} successful") return True else: print(f"Connection failed: error code {result}") return False finally: sock.close()

# Test common ports test_connection('localhost', 80) # HTTP test_connection('localhost', 443) # HTTPS test_connection('localhost', 5432) # PostgreSQL test_connection('localhost', 3306) # MySQL ```

Solution 1: Start the Server

```bash # If server is not running, start it

# HTTP server python -m http.server 8080 # Simple HTTP server

# Flask app python app.py # Or flask run

# Django python manage.py runserver 0.0.0.0:8080

# PostgreSQL sudo systemctl start postgresql

# MySQL sudo systemctl start mysql

# Redis redis-server

# Custom server python server_script.py ```

```python # Quick HTTP server in Python from http.server import HTTPServer, SimpleHTTPRequestHandler

server = HTTPServer(('localhost', 8080), SimpleHTTPRequestHandler) print("Starting server on port 8080...") server.serve_forever() ```

Solution 2: Verify Correct Port

```python import socket

# Problem: Wrong port sock = socket.socket() sock.connect(('localhost', 8000)) # Server on 8080

# Fix: Use correct port sock.connect(('localhost', 8080)) # Correct port

# Discover correct port def find_service_port(service_name): """Get standard port for service.""" ports = { 'http': 80, 'https': 443, 'ssh': 22, 'ftp': 21, 'postgresql': 5432, 'mysql': 3306, 'redis': 6379, 'mongodb': 27017, 'rabbitmq': 5672, } return ports.get(service_name.lower())

# Check config files for actual port import configparser config = configparser.ConfigParser() config.read('server.conf') port = config.getint('server', 'port', fallback=8080) ```

Solution 3: Check Host Address

```python import socket

# Problem: Wrong host sock.connect(('127.0.0.1', 8080)) # Server on different IP

# Fix: Check available addresses def find_server_addresses(port): """Find addresses listening on port.""" import subprocess result = subprocess.run(['ss', '-tlnp'], capture_output=True, text=True)

addresses = [] for line in result.stdout.split('\n'): if str(port) in line: parts = line.split() if len(parts) >= 4: addr = parts[3].split(':')[0] addresses.append(addr)

return addresses

# Or try all common addresses addresses = ['localhost', '127.0.0.1', '0.0.0.0', '::1'] for addr in addresses: try: sock = socket.socket() sock.settimeout(1) sock.connect((addr, 8080)) print(f"Connected to {addr}:8080") break except ConnectionRefusedError: continue ```

Solution 4: Handle Firewall Issues

```bash # Linux - Allow port sudo iptables -A INPUT -p tcp --dport 8080 -j ACCEPT

# Or using firewalld sudo firewall-cmd --add-port=8080/tcp --permanent sudo firewall-cmd --reload

# Or using ufw sudo ufw allow 8080/tcp

# Windows netsh advfirewall firewall add rule name="Allow 8080" dir=in action=allow protocol=tcp localport=8080 ```

```python # Python code to handle firewall gracefully def connect_with_retry(host, port, retries=5, delay=1): """Connect with retry logic.""" import time

for attempt in range(retries): try: sock = socket.socket() sock.settimeout(5) sock.connect((host, port)) print(f"Connected after {attempt + 1} attempts") return sock except ConnectionRefusedError: if attempt < retries - 1: print(f"Connection refused, retrying in {delay}s...") time.sleep(delay) else: print("Connection refused after all retries") raise ```

Solution 5: Bind Server to Correct Address

```python # Server code - bind to accessible address

# Problem: Server bound to 127.0.0.1 only server = HTTPServer(('127.0.0.1', 8080), handler) # Only localhost can connect

# Fix: Bind to all interfaces server = HTTPServer(('0.0.0.0', 8080), handler) # Any address can connect

# Flask example # app.run(host='0.0.0.0', port=8080) # Accessible from all

# Socket server example import socket

server_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server_sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) server_sock.bind(('0.0.0.0', 8080)) # Bind to all interfaces server_sock.listen(5)

print("Server listening on 0.0.0.0:8080") ```

Solution 6: Handle IPv4/IPv6 Mismatch

```python import socket

# Problem: IPv4 connection to IPv6 server sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) sock.connect(('localhost', 8080)) # Fails if server is IPv6

# Fix: Use IPv6 socket sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM) sock.connect(('::1', 8080)) # IPv6 localhost

# Fix: Use dual-stack (works for both) sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM) sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0) # Dual stack sock.connect(('localhost', 8080))

# Best: Use socket.create_connection (auto-selects) sock = socket.create_connection(('localhost', 8080)) ```

Solution 7: Implement Connection Pooling

```python import socket import time from queue import Queue

class ConnectionPool: """Pool of reusable connections."""

def __init__(self, host, port, pool_size=5, timeout=30): self.host = host self.port = port self.pool_size = pool_size self.timeout = timeout self.pool = Queue(maxsize=pool_size) self._initialize_pool()

def _initialize_pool(self): for _ in range(self.pool_size): try: sock = self._create_connection() self.pool.put(sock) except ConnectionRefusedError: print("Warning: Could not initialize full pool")

def _create_connection(self): sock = socket.create_connection((self.host, self.port), timeout=self.timeout) return sock

def get_connection(self): try: sock = self.pool.get(timeout=5) # Verify connection is still valid try: sock.send(b'') # Test return sock except: return self._create_connection() except: return self._create_connection()

def return_connection(self, sock): try: self.pool.put(sock, timeout=1) except: sock.close()

# Usage pool = ConnectionPool('localhost', 8080) conn = pool.get_connection() try: conn.send(data) finally: pool.return_connection(conn) ```

Solution 8: Use Connection Timeout Gracefully

```python import socket

def safe_connect(host, port, timeout=5, message=None): """Connect with comprehensive error handling.""" if message: print(f"Connecting to {host}:{port}...")

try: sock = socket.create_connection((host, port), timeout=timeout) if message: print("Connection successful") return sock

except ConnectionRefusedError: print(f"Connection refused by {host}:{port}") print("Possible causes:") print(" - Server not running") print(" - Wrong port number") print(" - Firewall blocking connection") return None

except socket.timeout: print(f"Connection timed out after {timeout}s") print("Possible causes:") print(" - Server overloaded") print(" - Network latency") return None

except socket.gaierror: print(f"Could not resolve hostname: {host}") return None

except OSError as e: print(f"OS error: {e}") return None

# Usage sock = safe_connect('localhost', 8080, message=True) if sock: # Use connection sock.close() ```

Service-Specific Troubleshooting

PostgreSQL

```python import psycopg2

def connect_postgresql(host='localhost', port=5432, dbname='postgres'): """Connect to PostgreSQL with error handling.""" try: conn = psycopg2.connect( host=host, port=port, dbname=dbname ) return conn except ConnectionRefusedError: print("PostgreSQL connection refused") print("Check if PostgreSQL is running:") print(" sudo systemctl status postgresql") print("Check PostgreSQL port:") print(" cat /etc/postgresql/*/main/postgresql.conf | grep port") raise ```

Redis

```python import redis

def connect_redis(host='localhost', port=6379): """Connect to Redis with error handling.""" try: client = redis.Redis(host=host, port=port) client.ping() # Test connection return client except redis.exceptions.ConnectionError: print("Redis connection refused") print("Check if Redis is running:") print(" redis-cli ping") print("Start Redis:") print(" redis-server") raise ```

HTTP/Web APIs

```python import requests from requests.exceptions import ConnectionError

def safe_request(url, timeout=5, retries=3): """Make HTTP request with error handling.""" for attempt in range(retries): try: response = requests.get(url, timeout=timeout) return response except ConnectionError as e: if 'Connection refused' in str(e): print(f"Server refused connection: {url}") if attempt < retries - 1: print("Retrying...") continue raise return None ```

Verification

After applying the fixes, verify that the ConnectionRefusedError is resolved by testing the connection:

```python import socket

def verify_connection(host, port): """Verify that connection works correctly.""" try: sock = socket.create_connection((host, port), timeout=5) print(f"Successfully connected to {host}:{port}") sock.close() return True except ConnectionRefusedError: print(f"Connection still refused to {host}:{port}") return False except Exception as e: print(f"Connection error: {e}") return False

# Run verification verify_connection('localhost', 8080) ```

Prevention

1.Check server status before connecting
2.Verify port number in configuration
3.Use connection retry logic for transient failures
4.Implement health checks in your clients
5.Use connection pools for repeated connections

```python # Good pattern: Connection with health check class ConnectionManager: def __init__(self, host, port): self.host = host self.port = port self._sock = None

def connect(self): """Establish connection.""" self._sock = socket.create_connection((self.host, self.port)) return self._sock

def is_connected(self): """Check if connection is valid.""" if not self._sock: return False try: self._sock.send(b'') return True except: return False

def reconnect(self): """Reconnect if needed.""" if not self.is_connected(): return self.connect() return self._sock

def close(self): """Close connection.""" if self._sock: self._sock.close() self._sock = None ```

ConnectionResetError - Connection closed by remote
socket.timeout - Connection attempt timed out
socket.gaierror - Hostname resolution failed
TimeoutError - Operation timed out

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Last updated: Nov 27, 2025

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How to Fix Python ConnectionRefusedError

Introduction

Symptoms

Basic ConnectionRefusedError

HTTP Request Connection Refused

Database Connection Refused

WebSocket Connection Refused

Common Causes

Step-by-Step Fix

Step 1: Check if Server is Running

Step 2: Check Port is Listening

Step 3: Check Firewall Rules

Step 4: Test from Python

Solution 1: Start the Server

Solution 2: Verify Correct Port

Solution 3: Check Host Address

Solution 4: Handle Firewall Issues

Solution 5: Bind Server to Correct Address

Solution 6: Handle IPv4/IPv6 Mismatch

Solution 7: Implement Connection Pooling

Solution 8: Use Connection Timeout Gracefully

Service-Specific Troubleshooting

PostgreSQL

Redis

HTTP/Web APIs

Verification

Prevention

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Python Troubleshooting FAQs

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How to Fix Python ConnectionRefusedError

Introduction

Symptoms

Basic ConnectionRefusedError

HTTP Request Connection Refused

Database Connection Refused

WebSocket Connection Refused

Common Causes

Step-by-Step Fix

Step 1: Check if Server is Running

Step 2: Check Port is Listening

Step 3: Check Firewall Rules

Step 4: Test from Python

Solution 1: Start the Server

Solution 2: Verify Correct Port

Solution 3: Check Host Address

Solution 4: Handle Firewall Issues

Solution 5: Bind Server to Correct Address

Solution 6: Handle IPv4/IPv6 Mismatch

Solution 7: Implement Connection Pooling

Solution 8: Use Connection Timeout Gracefully

Service-Specific Troubleshooting

PostgreSQL

Redis

HTTP/Web APIs

Verification

Prevention

Related Errors

Related Articles

People also search for

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