1. Error message: The TCP/IP connection to the host 100.xxx.xx.xx, port xxx has failed.
Error cause: The port number of the self-built database is incorrect, or the network is disconnected.
Solution: Ensure that the port number of the self-built database is correct and that the port is included in the security group rule and firewall whitelist. For details, see Modifying ECS Security Group Rules and Modifying Firewall Rules.