Simulating a slow network on a Mac

I ran across these very handy commands to simulate a connection of only 4kbps.  This is helpful when developing mobile applications in particular because some cell connections are horrible.

sudo ipfw pipe 1 config bw 4KByte/s
sudo ipfw add 100 pipe 1 tcp from any to me 3000

There are several interesting parts to these commands.

The 4KByte/s which can be whatever speed you want.  This is the bandwidth, measured in [K|M]{bit/s|Byte/s}.

The other interesting part is 3000.  This is the port that will be slowed.  Port 3000 is the default port on which Ruby on Rails listens.  If you are doing Java, you would probably want to use 8080.

The 100 is the rule number.  Useful when it comes time to delete this rule.

To clear out this pipe, simply type the following when finished:

sudo ipfw delete 100

To clear all custom rules, you could type:

sudo ipfw flush