# Self-Built Databases on ECSs

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.

Parent topic: Microsoft SQL Server