WifiGeckoReader allows you to view the gecko debug messages over the wifi connection. Only use this when debugging.  There is no need to use it regularly.  Set wifi_gecko=no when not needed.
It uses UDP port 4405.

To make it work with wiiflow, edit or add the following wiiflow.ini lines:

[DEBUG]
wifi_gecko=yes
wifi_gecko_port=4405

wifi_gecko_ip=your.computer.ipAddr.here
eg:
wifi_gecko_ip=192.168.0.199

Once this is done, run WifiGeckoReader, then run wiiflow.  You should start seeing debug messages.