How can pipeline agents(both self hosted & Microsoft hosted) communicate with on-prem target env?

Hi team,

I would like to know which protocol needs to be whitelisted on the target environment(On-premises) to fecilitate the communication between agents and target servers. I have a few on-premises servers where I want to deploy my application through automated pipelines. This will need the agents to be able to communicate to the target environment. How can I make sure that this communication happens and there aren't any firwall or network blocker preventing this.

Thanks 🙂