Relay Server acts as a reverse proxy for client devices communicating with the SAP Mobile Server cluster, and it provides load balancing for the SAP Mobile Server cluster.
Relay Servers are deployed on the DMZ subnet. With a corresponding Outbound Enabler (RSOE), Relay Server enables communication from the SAP Mobile Server cluster to client devices, via the Internet, without opening an inbound port on the internal firewall.
Each SAP Mobile Server instance is supported by one or more RSOEs. Each RSOE opens outbound connections to the Relay Server, to handle both inbound and outbound communication channels, on behalf of the SAP Mobile Server. Connections between the RSOE and Relay Server use HTTPS protocol.
Relay Server also provides load balancing for the SAP Mobile Server cluster by forwarding requests from client devices to SAP Mobile Servers in the cluster, by round-robin distribution. However, in most production deployment environments, multiple Relay Servers are used with a third-party load balancer, which provides complete load balancing and failover capability. In this case, Relay Servers are deployed as a farm, and you need to perform additional steps at the end of the file generation task.