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Home > Success Center > Network Performance Monitor (NPM) > NPM - Knowledgebase Articles > Polling server is unable to reach the host agent

Polling server is unable to reach the host agent

Created by Matthew Lamb, last modified by MindTouch on Jun 23, 2016

Views: 5,890 Votes: 1 Revisions: 4



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 [54] WARN  SolarWindsAMSProxy.Communications - Exception - error code [0x274d], context [File [SyncHttpExchangeClient.cpp], line [897]], messageSystem.Net.Sockets.SocketException (0x80004005): No connection could be made because the target machine actively refused it


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:

2016/01/15 12:36:10:139 PID: 1016 TID:   564 [ERROR] ProvisionClientLib::SignalRClientBase::OnError - Hub [FilesHub], SignalR error: Error code [windows:12029], Message: Error in: WinHttpSendRequest
2016/01/15 12:36:10:139 PID: 1016 TID:  2064 [WARN] w32_exception caught: Error [1627L], [ProvisionClientLib::SignalRClientBase::StartInternal - Hub [FilesHub] failed to connect to[]], File: ..\AsyncRpcCommon\AsyncRpcClientLoopImpl.cpp, Line: 201


  • NPM v11+
  • Port-restricted or firewall-restricted environment


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.



  1. Disable firewall or open necessary ports.
  2. Set client NIC to priority network device in binding order. 
  3. Free any port that is currently bound.
  4. For Server based communication, make sure that the port being used is correctly configured for the Agent in NPM:
    1. Go to Settings > Manage Agents.
    2. Locate and edit the affected agent.
    3. Click Advanced Options.
    4. Verify that the selected port is the one that you require.


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