You need to verify that the SSIM can connect to another system or SSIM on a specific port but SSIM 4.8.x does not include the telnet package.
Telnet was removed in order to meet CIS RHEL OS Hardening Standards.
You can test this connection using ssh. To use ssh for testing if a port is open and can be connected to from the SSIM run the command below:
ssh -v <Destination IP> -p <port>
For example, if I wanted to test the connection on port 443 from one of my test SSIM's to my other test SSIM at 10.167.28.224 I would use the command:
ssh -v 10.167.28.224 -p 443