WiFi shield can detect some transmission problems. The deault management provides a complete Arduino automatic reset if error is < 73.
But you can chose to manage error in customized way.
If you want manage error create a function and assign its name to a WiFi function pointer MWiFi.errorHandle
"errorHandle" function pointer has an argument that is the error code number:
void (*errorHandle)(int);
Example : MWiFi.errorHandle=myFun ; where myFun: void myFun(int code){....}
If ERRORLOG define is 1 : code is printed.
If code < 73 : reset . Else nothing.
N.B. Wi-Fi connection lost is not a error code and in this case reset is always performed (another routine manages this asyncronous event)