Probe-Central connection issues and their resolutions

The Probe-Central connection should be established for proper functioning of Network Configuration Manager Enterprise Edition. The Probe connection to the Central server can be checked in the corresponding Probe server under Settings > Configuration > Central Details.

Common problems faced with Probe-Central connection are discussed below.

I. ConnectException

  • Connection refused: connect :The Probe server is unable to contact the Central server port.

    Reason #1: The Central server port contacted by the Probe server is invalid.
    Reason #2: IP address of the Central server specified is wrong.
    Reason #3: The Central server is not running.

  • Connection Timeout:The Probe server could not establish a connection with the Central server.

    Reason #1: Network has connectivity issues.
    Reason #2: The Central server is overloaded with requests.
    Reason #3: The connection request is blocked by Windows Firewall.

  • Connection Failure :The Probe server is unable to establish connection with the Central server. Verify the protocol the Probe server uses for communication.

    Reason: The protocol configured in the Probe server is wrong.

II. SocketException

  • No route to host: connect :The Probe server is unable to find a path to contact the Central server.

    Reason #1: The connection is not established due to routing issues.
    Reason #2: The network connection has been changed.

  • UnknownHostException:The probe server is unable to identify the Central server.

    Reason #1: IP address of the given host name is not found.
    Reason #2: There is a problem with address resolution.

  • Connection reset:The Probe server request is not received by the Central server.

    Reason: Firewall in the Central server network is blocking the Probe server connection request.

  • Connection timed out:The Central server is unable to respond to the request of the Probe server.

    Reason: The Central server is unable to respond due to outbound firewall rules.

  • No Buffer space available:Probe server could not establish a connection.

    Reason: Ports in the Probe server are unavailable for establishing a connection with the Central server.

III. IOException

  • HTTP response code 400:Server returned HTTP response code: 400 for the specified URL.

    Reason: There is no such available host.

These connection issues can be rectified by following the troubleshooting steps given below.

Step 1: Verify the Central server details

Check if the Central server details specified in the Probe server (under Settings > Configuration > Central Details) are valid. If not, provide the valid details.

Step 2: Verify the Probe-Central connection

Check if the connection is established between the Probe and the Central servers using ping and netstat commands. If not, fix the issue causing the connection failure.

Step 3: Check port status

Check if the port is occupied by another service/application using utility tools such as Resource Monitor for Windows and netstat command for Linux.

Step 4: Analyze data packets

Analyze data packets using a packet analyzer and check if

  • The data is sent from Probe and received by the Central server
  • The Central server is responding to the request from the corresponding probe.
  • The Probe server is receiving the response

If not, fix the issue.

Step 5: Check firewall

Disable firewall and check if data transfer occurs (Case: when connection check passes and data transfer fails)

If the above steps do not work, please contact ncm-support@manageengine.com, with the following details:

  • Packet capture data
  • Screenshot of Step 2

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