Can't reach SSM port-forwarded service within docker

Question

Hi,
I'm connecting to a remote DB with a port forward (with [AWS ssm][1], `AWS-StartPortForwardingSessionToRemoteHost`): `aws ssm start-session --target i-XXXXX --document-name AWS-StartPortForwardingSessionToRemoteHost --parameters '{"portNumber":["5432"],"localPortNumber":["5432"], "host":["XXXXX.rds.amazonaws.com"]}'`

The connection locally works fine:
```
$ telnet localhost 5432
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
```

But if I try to reach it within docker, it doesn't work:

```
$ docker run --add-host host.docker.internal:host-gateway mikesplain/telnet host.docker.internal 5432
telnet: can't connect to remote host (172.17.0.1): Connection refused
```

I'm in a situation where **I can't use** `--network=host`.

Am I missing something here ?

Seems strongly related to https://stackoverflow.com/questions/69222946/access-aws-ssm-port-inside-docker-container

Thanks,

[1]: https://docs.aws.amazon.com/systems-manager/latest/userguide/session-manager-working-with-sessions-start.html#sessions-remote-port-forwarding

RobinF · Accepted Answer

https://stackoverflow.com/a/76705498/5692012

Riku_Kobayashi · Answer

The following commands would need to be running on the back end to start the container.  
Are you able to start the container with the port-forward tunnel open?  
```
aws ssm start-session --target i-XXXXX --document-name AWS-StartPortForwardingSessionToRemoteHost --parameters '{"portNumber":["5432"],"localPortNumber":["5432"], "host":["XXXXX.rds.amazonaws.com"]}'
```

Can't reach SSM port-forwarded service within docker

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