Hi there, thanks for your question.
First of all, can I just let you know about a couple of sources of information in case they help answer your queries:
Hi gh0st , it looks to me like your client is also in a docker container. This is fine, but you may want to consider launching the container with --net=host so that you get the public IP address pushed down to the client, not the 172.17 address.
In terms of the direction of traffic, since PMM uses Prometheus for metrics collection, this service is pull-based, meaning PMM Server initiates connections to the exporter. Therefore if you’re using docker for your clients you then need to make sure you enable the correct -p passthrough for network communications, and also ensure that the host’s firewall is permitting traffic on the open ports. For example 42000 is the port for linux metrics (node_exporter) and 42002 is the port for MySQL metrics (mysqld_exporter).