Lots of things changed under the hood in MacOS high sierra. One of those was to enable a sandbox like environment and to remove insecure communication protocols. This breaks things like console communication to the network modeling and virtualization platform Eve-NG. It’s fairly trivial to re-enable it, however. This can be accomplished by doing the following steps.
1. Reboot your Mac and hold the CMD + R keys
2. When presented with the recovery options, click Utilities at the top and choose Terminal
3. Type; csrutil disable
4. Reboot as normal
6. terminal and type;
brew install telnet
sudo ln -s /usr/local/bin/telnet /usr/bin/telnet
7. Again, Reboot your Mac and hold the CMD + R keys
8. When presented with the recovery options, click Utilities at the top and choose Terminal
9. Type; csrutil enable
10. Reboot as normal
You’re done. You can have telnet for your internal communication to Eve-NG consoles. Don’t use it to talk to production network gear, because it’s not 1998.