Using Telnet to test connectivity

[LocNguyen]

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.

1. Open Windows Command Prompt
2. Enter :telnet <address_of_remote_server> <port_number>" - telnet 192.168.1.2 443
   1. Result if Port open: blank window with blinking cursor
   2. Result if Port closed: error message displayed similar to "Connecting To 192.168.1.2…Could not open connection to the host, on port xx: Connect failed"
3. The example above test for connectivity against the remote server that has the IP address of 192.168.1.2 over port 443