Telnet has been removed from Mac OS High Sierra, but can still be useful for developers to check ports are open etc.
If you need to enable it, you can do so with Homebrew:
Homebrew Telnet
Update (10/10/17): I received an email from David Waitzman in which he notes you can get telnet from an old Time Machine backup and then copy it into /usr/local/bin – I’d recommend that options too if you have a backup.
使用 homebrew 安装telnet brew install telnet 查看是否安装成功 shifeiyandeMacBook-Pro: shifeiyan$ telnet telnet 到这一步就安装完成了. Telnet使用 shifeiyandeMacBook-Pro: shifeiyan$ telnet www.baidu.com 80 Trying 115.239.210.27. Connected to www.a.shifen.com. Escape character is '^'. Homebrew-core / Formula / telnet.rb / Jump to. Code definitions. Telnet Class install Method. Code navigation index up-to-date Go to file Go to file T; Go to line L; Go to definition R; Copy path Cannot retrieve contributors at this time. 58 lines (47 sloc) 2.08 KB Raw Blame. Homebrew’s package index. ShawnstationdeMacBook-Pro: shawnstation$ brew -version Homebrew 1.6.9 Homebrew/homebrew-core (git revision fab7d; last commit 2018-07-07) catalina homebrew Share. Homebrew จะดาวน์โหลดและติดตั้ง Telnet จากนั้นคุณสามารถเรียกใช้คำสั่ง Telnet ใด ๆ ได้อย่างง่ายดายโดยไม่มีข้อผิดพลาด.
Update (25/11/17): I received a second email from Michael Bazik which details how you can install the telnet client directly from GNU provided tarballs:
Update (05/01/18): Jonny Bradley emailed in to address an issue with installing non homebrew telnet. If you encounter the error:
then you’ll need to chmod ping to allow it permission to run with:
Homebrew Telnet Install
Update (08/02/18): Matthew Ward got in touch to say that you can compile telnet without all of the other gunk that still comes with Mac OS, using the following: