Use begin/dataflow to log allocated ports and statevecs

examples/netstack/port-allocator.rkt

@@ -18,8 +18,8 @@
           (define local-ips (query-local-ip-addresses))
           (define used-ports (query-used-ports))
 
-          ;; TODO: How can I get this to run whenever used-ports changes?
-          ;; (log-info "port-allocator ~v used ports: ~v" allocator-type new-used-ports)
+          (begin/dataflow
+            (log-info "port-allocator ~v used ports: ~v" allocator-type (used-ports)))
 
           (on (message (port-allocation-request $reqid allocator-type))
               (define currently-used-ports (used-ports))

examples/netstack/tcp.rkt

@@ -200,9 +200,10 @@
              (else #f))))
         (else #f)))
 
-    ;; TODO: again, want to print this when local-ips or
-    ;; active-state-vectors change.
-    ;; (log-info "gestalt yielded statevecs ~v and local-ips ~v" statevecs local-ips)
+    (begin/dataflow
+      (log-info "SCN yielded statevecs ~v and local-ips ~v"
+                (active-state-vectors)
+                (local-ips)))
 
     (define (deliver-outbound-packet p)
       (match-define (tcp-packet #f