### Understand the alert

The `portcheck_connection_timeouts` alert calculates the average ratio of connection timeouts when trying to connect to a TCP endpoint over the last 5 minutes. If you receive this alert, it means that the monitored TCP endpoint is unreachable, potentially due to networking issues or an overloaded host/service.

This alert triggers a warning state when the ratio of timeouts is between 10-40% and a critical state if the ratio is greater than 40%.

### Troubleshoot the alert

1. Check the network connectivity
   - Use the `ping` command to check network connectivity between your system and the monitored TCP endpoint.
   ```
   ping <tcp_endpoint_ip>
   ```
   If the connectivity is intermittent or not established, it indicates network issues. Reach out to your network administrator for assistance.

2. Check the status of the monitored TCP service
   - Identify the service running on the monitored TCP endpoint by checking the port number.
   - Use the `netstat` command to check the service status:

   ```
   netstat -tnlp | grep <port_number>
   ```
   If the service is not running or unresponsive, restart the service or investigate further into the application logs for any issues.

3. Verify the load on the TCP endpoint host
   - Connect to the host and analyze its resource consumption (CPU, memory, disk I/O, and network bandwidth) with tools like `top`, `vmstat`, `iostat`, and `iftop`.
   - Identify resource-consuming processes or applications and apply corrective measures (kill/restart the process, allocate more resources, etc.).

4. Examine the firewall rules and security groups
   - Ensure that there are no blocking rules or security groups for your incoming connections to the TCP endpoint.
   - If required, update the rules or create new allow rules for the required ports and IP addresses.

5. Check the Netdata configuration
   - Review the Netdata configuration file `/etc/netdata/netdata.conf` to ensure the `portcheck` plugin settings are correctly configured for monitoring the TCP endpoint.
   - If necessary, update and restart the Netdata agent.

### Useful resources

1. [Netstat Command in Linux](https://www.tecmint.com/20-netstat-commands-for-linux-network-management/)
2. [Iostat Command Usage and Examples](https://www.thomas-krenn.com/en/wiki/Iostat_command_usage_and_examples)
3. [Iftop Guide](https://www.tecmint.com/iftop-linux-network-bandwidth-monitoring-tool/)