telnet nc command returns "Connection failed"
When usingncOrderortelnet commandWhen testing the host port
If "connection refused" and "connection failed" error is returned
This may be due to several reasons:
1. The port is not listened
telnet is a tool for testing network connections that requires the target port to be listening and accepting connections. If the port is not listened in Linux and no service is running on the specified port, you will not be able to connect to the port via telnet.
Trying to connect to the port using nc will result in a "connection refused" error.
If you try to connect to an unlisted port using telnet, you will receive an error message similar to "Cannot connect" or "Connection timeout".
Therefore, before telnet connects to a specific port, make sure that the target port is correctly configured and listened in the Linux system. You can use the netstat command or similar tool to check if the port is listening
2. Firewall policy
The firewall blocks the port:
- The firewall settings on the target host may deny attempts to connect to the port.
- You can check the host's firewall configuration and make sure that connection traffic from that port is allowed to pass.
3. The target host does not accept external connections
Some services may be configured to allow only connections to specific IP addresses or subnets.
If your IP address is not on the whitelist, attempting to connect to the port may be denied.
In summary:
The "connection refused" error does not mean that there is something wrong with your command, but indicates that the port on the target host is not in a listening state or that the connection is blocked by the firewall.
Summarize
The above is personal experience. I hope you can give you a reference and I hope you can support me more.