How to Fix Connection Timed Out, Connection Refused, and Network Unreachable Errors

Timeout vs Refused vs Unreachable — What Is the Difference?

All three errors indicate a failed connection attempt, but they tell you very different things about where the failure occurred:

Common Causes

Diagnosing the Error

Run these commands in order to narrow down the cause:

1. Ping the host

Confirms whether the host is reachable at the network level:

ping -c 4 example.com

2. Check if the port is open (telnet / nc)

If ping works but the connection still fails, the port may be blocked or the service may be down:

# Test if port 443 is open
telnet example.com 443

# Or with netcat (nc)
nc -zv example.com 443

3. Trace the network path

Identifies where in the network the packets are being dropped:

# Linux / macOS
traceroute example.com

# Windows
tracert example.com

4. Check what is listening on the server

Run this on the server itself to confirm the service is running and bound to the right address:

# Linux — show all listening TCP ports
ss -tlnp

# Or with netstat
netstat -tlnp | grep LISTEN

Fixing Connection Timed Out

Check firewall rules

The most common cause. Check both the server's local firewall and any cloud security groups:

# Check iptables rules (Linux)
sudo iptables -L -n -v | grep DROP

# Check UFW status
sudo ufw status verbose

# Allow a port through UFW
sudo ufw allow 443/tcp

Check cloud security groups

If your server is on AWS, Azure, or GCP, check that the security group / network security group allows inbound traffic on the required port from the client's IP range.

Check server load

# Check CPU and memory
top

# Check if the service is running
systemctl status nginx
systemctl status apache2

Fixing Connection Refused Error

Start or restart the service

# Restart Nginx
sudo systemctl restart nginx

# Restart Apache
sudo systemctl restart apache2

# Restart a Node.js app via PM2
pm2 restart app-name

Check the service is binding to the right address

A service bound to 127.0.0.1 is only accessible locally. It must bind to 0.0.0.0 to accept external connections:

# Check what address Nginx is listening on
ss -tlnp | grep nginx

# In Nginx config — listen on all interfaces:
listen 0.0.0.0:443 ssl;

Check service logs for crash reason

# Nginx error log
sudo tail -50 /var/log/nginx/error.log

# Systemd journal for the service
sudo journalctl -u nginx -n 50 --no-pager

Fixing Network Unreachable

Check your routing table

# Linux
ip route show

# Windows
route print

Look for a default route (0.0.0.0/0). If it is missing, your machine has no gateway configured.

Add a default gateway

# Temporarily add a default route (Linux)
sudo ip route add default via 192.168.1.1

# Permanently (edit /etc/network/interfaces or netplan config)
gateway 192.168.1.1

Restart the network interface

# Linux (NetworkManager)
sudo systemctl restart NetworkManager

# Or bring the interface down and up
sudo ip link set eth0 down && sudo ip link set eth0 up

Prevention and Monitoring

• Document your firewall rules — keep a record of which ports are open and why. Undocumented rules get forgotten and cause outages when servers are rebuilt.
• Use process supervisors — run services under systemd, PM2, or Supervisor so they restart automatically if they crash.
• Set up health checks in your load balancer — so traffic is automatically routed away from unhealthy instances.
• Monitor with Alive24x7 — TCP port monitors check whether your ports are open every minute. If a service stops accepting connections, you get an instant alert before users notice.

Frequently Asked Questions