Im using release 1.6.5-947-g39819f0 on my Mac.
Using the example NTP UDP client in the package I can set the port to 2390, indeed reading the port back returns the same port number, however my router which I'm currently using as an NTP time sever logs as request with the source port of 4097 thus the NTP request fails.
I noticed this is an intermittent issue as it some times works ok and the stats in my router show the request from 2390 which is the port I set in the code.
Happy to post code however I several include files and not sure if there is a posting limit.
Any feedback would be greatly appreciated.