changes in udp crashes in server side code

CHANGELOG

@@ -1,5 +1,12 @@
 # CHANGELOG
 
+
+- 20211020
+
+    		Tidy-up server shutdown
+
+    		Trying to find cause of lockup when client disappears
+
 - 20211006
 
     		Send TX/Freq changes multiple times with rigctld

WHATSNEW

@@ -15,3 +15,5 @@ The following highlights are in this 1.x-release:
         when we use rigctld. 
 
         people should use "fake it" in wsjtx as the split code is not reliable.
+
+        tidied up udp server function for better reliability