How to diagnose a 'Connection refused' error when connecting to a service on the same machine?
sobes.tech AI
Answer from AI
The "Connection refused" error when trying to connect to a service on the same machine means that the client cannot establish a TCP connection because the server either is not listening on the specified port or the connection is being blocked.
For diagnostics:
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Check if the service is running and listening on the required port:
netstat -tuln | grep <port> # or ss -tuln | grep <port>If the port does not appear, the service is not running or is listening on a different port.
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Check firewall settings: Ensure that local connections to this port are not blocked.
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Check which interface the service is listening on: Sometimes the service listens only on localhost (127.0.0.1), while the client tries to connect via another IP, or vice versa.
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Check the service logs: The service may have crashed or failed to initialize correctly.
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Verify the address and port in the client: Configuration errors can lead to attempts to connect to the wrong port.
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Use connection testing utilities:
telnet 127.0.0.1 <port> # or nc -vz 127.0.0.1 <port> -
Check SELinux/AppArmor: In some systems, they may block connections.
Thus, diagnostics start with verifying that the service is indeed running and listening on the required port, then checking the network stack and security settings.