Connecting to a remote server using PuTTY is a routine task for developers, system administrators, and IT professionals. However, it’s not uncommon to encounter errors, with one of the most frustrating being the infamous “Network error: Connection refused” message. This error can bring productivity to a grinding halt if not addressed properly. Fortunately, it’s usually fixable with systematic troubleshooting. This article will explore common causes and provide a thorough guide on solving this issue on Windows systems.
Understanding the “Connection Refused” Error
Before diving into solutions, it’s essential to understand what the “Connection refused” error actually means. This message typically occurs when PuTTY successfully reaches the desired server or IP address, but the server actively denies the connection attempt.
This is different from a timeout or DNS resolution error—in fact, a “connection refused” response usually indicates that the network path is fine, but something on the destination side is rejecting the request.
Common Causes and How to Fix Them
1. SSH Service Not Running on the Server
PuTTY uses the SSH protocol for secure remote login. If the SSH service (sshd) is not running or installed on the server, the client cannot establish a connection.
- On Linux: Connect to the server locally and run
sudo systemctl status sshorsudo service ssh status. - Solution: If inactive, start the SSH service with
sudo systemctl start ssh.
If you’re attempting to reach a non-Linux system (such as Windows running SSH), ensure that the SSH server software (like OpenSSH for Windows) is installed and running.
2. Incorrect Port Number
By default, PuTTY uses port 22 for SSH connections. However, some servers are configured to use a different port to enhance security.
- Check the server settings or contact your administrator to confirm the port number and update it in PuTTY accordingly.
[ai-img]putty configuration port settings[/ai-img]
3. Firewall Blocking the Connection
Firewalls on either your local machine or the server can block TCP port 22 (or your custom SSH port), leading to a refused connection.
- Ensure that outbound SSH connections are allowed on your local Windows Firewall or antivirus software.
- Check the server’s firewall rules (like UFW, firewalld, or iptables on Linux) to confirm SSH access is allowed from your IP.
4. Incorrect IP Address or Hostname
It might seem obvious, but always double-check the IP address or domain name you’ve entered in PuTTY. A common mistake is a typo in the destination which could route your request to the wrong server, one that’s not expecting SSH traffic.
- Use the
pingortracertcommand to verify network connectivity.
5. Server-Side Restrictions
In some cases, you may be restricted based on IP allowlisting or failed login attempts from your IP. Hosting providers and cloud platforms often have automated systems that block repeated failed login attempts.
- Check if your IP has been blocked on the server using tools like
fail2banor sshd logs. - Try connecting from a different network to determine if the problem is IP-specific.
6. Router or ISP Restrictions
Some networks, especially in public places like schools or coffee shops, may block SSH traffic altogether. Similarly, certain ISPs implement restrictions on outbound port 22 traffic.
Try switching to a mobile hotspot or VPN and see if the issue persists. If connecting works over these alternatives, then it’s time to investigate the network or ISP-level filters.
Additional Diagnostic Tools
For advanced troubleshooting, consider using additional tools:
- Telnet: Try
telnet [hostname] 22from the command prompt to test if the port is open. - Netcat (nc): If installed, it can be used to check open ports and banner grabbing.
- Wireshark: Useful for analyzing packet flows and identifying blocked or rejected traffic.
[ai-img]windows telnet command screenshot[/ai-img]
Pro Tips for Avoiding Future Errors
- Keep PuTTY updated to ensure compatibility with modern SSH configurations.
- Save your session configurations with verified IPs, ports, and settings to minimize entering incorrect information.
- Use SSH keys to enhance security and avoid brute-force bans.
Conclusion
The PuTTY “Connection refused” error might be frustrating, but it’s typically due to a configuration mishap, firewall issue, or service unavailability. With a systematic approach—like checking server status, verifying ports, and eliminating network barriers—you can resolve the issue efficiently. Understanding the root cause not only helps in resolving the current error but also prepares you to handle similar problems in the future with confidence.
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