This article describes how to address the issue when the DPI or its host agent cannot be reached by the poller server.
The DPI plugins depend on the agent service on the client to be able to communicate with the poller at all times. Whether it's an agent based communication or server based communication, the ports necessary for these two to speak must be accessible.
Necessary port requirements for DPI and Agents are listed in Port Requirements for SolarWinds Products.
The following is a common error from the Agent side:
2016-01-14 14:43:55,236  WARN SolarWindsAMSProxy.Communications - Exception - error code [0x274d], context [File [SyncHttpExchangeClient.cpp], line ], messageSystem.Net.Sockets.SocketException (0x80004005): No connection could be made because the target machine actively refused it 10.110.68.205:17790
To fix this error:
1. The port maybe blocked on the client server
2. The agent is in Passive Mode using port# 17790 so make sure Firewall is blocking that port
The following is an error displayed from the poller side:
This occurs when ports are blocked or inaccessible for the application and agent, or the port being used for server-based communication is incorrect. These ports must be opened and working to allow communication to work, whether it's a server-initiated or agent-initiated based communication.