Accepting incoming network connections makes iOS Simulator tests run significantly slower

I’m running tests for an iOS app on the Simulator (8.1). I am on version Appium v1.3.2-beta2, though this was also observed in Appium v1.3.1.

The app I am testing accepts incoming network connections. If I allow these connections through Apple’s Firewall (or turn off Apple Firewall so that they are always allowed) my tests run significantly slower. Each individual command seems to take longer to get sent to the Appium server.

A test that took 52.04 seconds to run when the network connections were blocked took 4 minutes 31.2 seconds to run when the network connections were allowed. On another machine, the Appium server timed out because commands were taking too long to arrive.

I thought this was kind of odd. Any thoughts as to why this might be happening?