Hi Mohan,
Please test the below to confirm issue and verify Endpoint Agent to Endpoint Server communication is over port 8000 by default. This port can be changed in the UI, under the Endpoint Server configuration page:
If your Endpoint server IP address is, 192.168.2.52 You can perform the following telnet test from a endpoint agent that is not checking in.
open a Command window:
telnet 192.168.2.52 8000
<If the port is open, this command should take you to a blank screen, if it is blocked you will receive a connection refused message>
Another good test you can perform from the Endpoint Agent is a netstat test which will show you what ports are connected/established or listening.
The endpoint server should be listening on port 8000 (0.0.0.0:8000 LISTENING), The endpoint agent, if connected will show ESTABLISHED on port 8000
Example From Endpoint server:
<Endpoint Server> C:\>netstat -aon | find "8000"
TCP 0.0.0.0:8000 0.0.0.0:0 LISTENING 2192
TCP 192.168.2.52:8000 192.168.2.53:1433 ESTABLISHED 2192
TCP 192.168.2.52:8000 192.168.2.54:49306 ESTABLISHED 2192
TCP 192.168.2.52:8000 192.168.2.55:49160 ESTABLISHED 2192
<The endpoint server example above shows that the server is listening on port 8000, and that 3 Endpoint Agents are ESTABLISHED (192.168.2.53,54,55)>
You can perform the same test from the Endpoint Agent. Here are the type results you "should" see if the agent is connected.
<Endpoint Agent> C:\>netstat -aon | find "8000"
TCP 192.168.2.53:1433 192.168.2.52:8000 ESTABLISHED 2016
Also refer the below links to download and test
https://www-secure.symantec.com/connect/downloads/required-tools-troubleshoot-dlp-endpoint-agents-v11