Diagnose Lindorm Network Issues with Telnet Port Testing - Lindorm

Use the telnet command to verify whether an Elastic Compute Service (ECS) instance can reach a Lindorm instance on a specific port. This is useful when a ping test succeeds but a connection issue persists — telnet checks port-level reachability and confirms whether the service port is accessible.

Prerequisites

Before you begin, ensure that:

On Linux: the telnet client is installed on the ECS instance
On Windows: the Telnet client feature is enabled on the ECS instance

Test port connectivity

View the endpoint of the Lindorm instance. Note the host (domain name) and port number.
Log in to the ECS instance and run the following command:
```
telnet <host> <port>
```
Replace <host> with the domain name from the endpoint, and <port> with the port number. The command works on both Linux and Windows. Example (Lindorm time series engine endpoint):
```
telnet ld-bp1mq0tdzbx1m****-proxy-lindorm-pub.lindorm.aliyuncs.com 33060
```
Check the output. In this example, the endpoint of the Lindorm time series engine is used.

Interpret the result

If telnet connects successfully but the application still cannot connect to Lindorm:

The network path between the ECS instance and the Lindorm instance is working as expected. The issue is likely in the application layer. Check the following:

Client configuration (connection string, credentials, driver version)
Application-level errors in your service code
Lindorm service-level restrictions (for example, IP allowlist or throttling)

See Lindorm connection issues and solutions for a full list of known issues and fixes.