We have a design using a K60f120 and MQX 4.02 with an FTP server, Telnet server and a periodic UDP broadcast. We're using the Atheros AR4100 Wi-Fi chip and the driver that currently only supports MQX 220.127.116.11 (support for 4.1 has apparently been developed but is caught up with "marketing and lawyers").
Our FTP server uses an MFS mounted to an SD card to allow us to copy files off of the SD card from an application running on a host PC; the Telnet server implements a command interface for the application on the PC; and the UDP broadcast is used as a keep alive and to convey the IP address and SSID to the host application so it knows which devices are available on the network to connect to.
We've got everything running rather nicely except for when the Wi-Fi signal fades out. After some period of time running with a poor Wi-Fi signal the UDP (which opens and closes a socket every second to perform it's broadcast) can no longer obtain a socket to connect to. Looking at the sockets that are currently allocated in this condition reveals that there are some sockets allocated to FTP and Telnet, but none free. If we don't limit the maximum number of TCP connections then we end up running out of memory in our application. Funnily enough, Telnet usually keeps on chugging along with no problems.
Given the information we've gathered so far, it looks FTP is using up all of the available sockets and not releasing them. We've tried playing around with the TCP and FTP timeouts to no avail.
I've seen others in this forum complain about similar issues and the answer is usually to move to MQX 4.1, but unfortunately we are limited to MQX 4.0 due to our use of the AR4100 and its lack of support for 4.1.