Probe-Central connection issues and their resolutions

The Probe-Central connection should be established for proper functioning of OpManager 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.

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 opmanager-support@manageengine.com, with the following details:

  • Packet capture data
  • Screenshot of Step 2