An easy way to add a serial port to your Mac is to buy a USB-to-Serial Adaptor. These adaptors are quite cheap and work.
A common chip used in USB-to-Serial Adaptors is the PL-2303. Drivers for Windows, Linux and Mac OS X are available. My advice is to get a PL-2303 based adaptor.
I got a generic adapter from eBay for 9.90 euros.
The goal of this project is to provide a Prolific PL2303 USB serial adapter driver for Mac OS X. This chip is used in various devices like usb serial dongles and as cheap embedded USB bridge in cellphones, GPS receivers and other applications with low data traffic.
从我两三年前接触 SSH 的时候我就在文档上见过 SSH tunnel 相关的东西，然而当时没有怎么看明白，也就一直没有深究，直到最近需求越来越多了，才终于发现这个东西原来这么有用，于是记录在此。