Dynatrace OneAgent is essentially a set of specialized processes running on each monitored host. Dynatrace OneAgent collects metrics from the operating system it runs in, analyzes host performance to determine whether or not there are any anomalies in comparison to baseline performance, and reports the most important metrics back to the Dynatrace Server.
Additionally Dynatrace OneAgent detects which processes run on each host and collects performance metrics for the most important processes. Dynatrace OneAgent can also monitor specific technologies (Java, Node.js, .NET, and more) in greater detail by injecting itself into those processes and monitoring them from the inside. This provides you with code level insight into the services that your application relies on.
Communication from Dynatrace OneAgent to Dynatrace Server is outbound only—Dynatrace Server never initiates communication with Dynatrace OneAgent. So there is no need to open ports for inbound communication when using Dynatrace. Dynatrace OneAgent can communicate directly to Dynatrace Server or it can communicate via a Dynatrace Security Gateway. Security Gateways allow you to limit the number of hosts in your datacenter that send outbound communications to Dynatrace Server, making firewall configuration more manageable in large environments. Security Gateways can additionally collect information from vCenter installations. Even without a Security Gateway however, all communication to Dynatrace Server is secured using strong encryption mechanisms.