Issue How to use the Telnet command to troubleshoot network connectivity and check for blocked network ports. Product Line TAC INET, TAC Vista, Andover Continuum, Satchwell MicroNet, Satchwell Sigma, TAC IA Series, Field Devices, EcoStruxure Building Operation, Other, Pelco, EcoStruxure Building Expert, Access Expert, Security Expert Environment TCP/IP Communication Command Prompt Telnet Command Cause Suspect certain network ports are blocked and need to verify Resolution Note:- Telnet operates using the TCP protocol. UDP connectivity cannot be tested using Telnet.