Question
How can I verify communication over a specific port using the Telnet Client?
Prerequisite
Install the Telnet Client on the server from which you want to test your connection.
Answer
- On the server from which you'd like to test communication, open a Command Prompt
- Run the command
telnet
- Watch to see if you get a response (typically indicated by strings of gibberish) or if the connection fails
Example:
To see if your Site Server machine "mySiteServer" can communicate with the Agent installed on "myAgent" over port 3999, you'd run the command telnet myAgent 3999
from "mySiteServer".
If you receive a response similar to the screenshot below, it indicates communication is open over port 3999 between "mySiteServer" and "myAgent":
If you receive a message like "Connect Failed", there is something between "mySiteServer" and "myAgent" blocking communication over port 3999 (firewall, security software, etc).
Overview
The Telnet Client can be used as a sort of super-ping, allowing you to initiate communication to a target over a desired port to look for a response.