diff --git a/racketmq/config.rkt b/racketmq/config.rkt
new file mode 100644
index 0000000..30c1651
--- /dev/null
+++ b/racketmq/config.rkt
@@ -0,0 +1,32 @@
+#lang syndicate/actor
+;; Server Configuration
+
+(provide (struct-out config)
+         spawn-configuration
+         define/query-config
+         config-ref)
+
+(require racket/file)
+(require/activate syndicate/drivers/filesystem)
+
+(struct config (item) #:prefab)
+
+(define (spawn-configuration path)
+  (actor #:name (list 'configuration-monitor path)
+         (during (file-content path file->list $items)
+           (log-info "config ~s: ~s" path items)
+           (for [(item items)]
+             (assert (config item))))))
+
+(define-syntax define/query-config
+  (syntax-rules ()
+    [(_ id default)
+     (define/query-config id id default)]
+    [(_ id key default)
+     (define/query-value id default (config (list 'key $val)) val)]))
+
+(define (config-ref key default)
+  (react/suspend (k)
+                 (define/query-value actual default (config (list key $val)) val)
+                 (on-start (flush!)
+                           (k (actual)))))
diff --git a/racketmq/defaults.rktd b/racketmq/defaults.rktd
new file mode 100644
index 0000000..2ded0b5
--- /dev/null
+++ b/racketmq/defaults.rktd
@@ -0,0 +1,22 @@
+;; REQUIRED:
+;; (canonical-host "localhost" 7827)
+
+;; OPTIONAL:
+
+;; (accepted-host "localhost" 7827)
+;; (accepted-host "localhost" 80)
+;; etc.
+
+(max-upstream-redirects 5)
+
+(min-poll-interval 60)
+
+(default-lease 86400) ;; seconds
+
+(default-poll-interval "none") ;; seconds, or "none"
+
+(max-dead-letters 10)
+(max-delivery-retries 10)
+(initial-retry-delay 5.0) ;; seconds
+(retry-delay-multiplier 1.618)
+(max-retry-delay 30)
diff --git a/racketmq/protocol.rkt b/racketmq/protocol.rkt
new file mode 100644
index 0000000..29fa88f
--- /dev/null
+++ b/racketmq/protocol.rkt
@@ -0,0 +1,60 @@
+#lang racket/base
+;; Assertions, Messages and Protocols for RacketMQ
+
+(provide (struct-out notification)
+         (struct-out update-subscription)
+         (struct-out subscription)
+         (struct-out subscription-settings)
+         (struct-out local-topic-config)
+         (struct-out topic-demand)
+         (struct-out local-topic-demand)
+         (struct-out local-host)
+         (struct-out canonical-local-host))
+
+;; A Topic is a URIString.
+
+;; A Deadline is an (Option Number), where #f indicates "unbounded",
+;; and numbers indicate a moment in time as a Unix epoch timestamp as
+;; might be returned from `current-seconds`.
+
+;; A Notification contains both `topic-name`, indicating the *local*
+;; name for the topic that is being subscribed to, as well as
+;; `canonical-topic`, which is the rel=self URL given by the upstream
+;; topic itself. The former is our local key for finding resources;
+;; the latter is a property of the topic content, not a property of
+;; the subscription. The same is true of `canonical-hub`: it pertains
+;; to the topic, not the subscription. The `topic-name` is the only
+;; field pertaining to a subscription; all the others pertain to the
+;; content.
+(struct notification (topic-name ;; Topic
+                      canonical-hub ;; Option URLString
+                      canonical-topic ;; Option Topic
+                      content ;; Bytes
+                      content-type) ;; Option String
+  #:prefab) ;; MESSAGE
+
+;; (update-subscription Topic URLString (Option SubscriptionSettings))
+(struct update-subscription (topic callback settings) #:prefab) ;; MESSAGE
+
+;; (subscription Topic URLString SubscriptionSettings)
+(struct subscription (topic callback settings-) #:prefab) ;; ASSERTION
+
+(struct subscription-settings (expiry-deadline ;; Deadline
+                               secret ;; Option Bytes
+                               poll-interval-seconds) ;; Option Number
+  #:prefab)
+
+;; (local-topic-config Topic (Option Number) (Option Number))
+(struct local-topic-config (name max-age max-count) #:prefab) ;; ASSERTION
+
+;; (topic-demand Topic (Option Number))
+(struct topic-demand (topic-name poll-interval-seconds) #:prefab) ;; ASSERTION
+
+;; (local-topic-demand String)
+(struct local-topic-demand (name) #:prefab) ;; ASSERTION
+
+;; (local-host String)
+(struct local-host (name port) #:prefab) ;; ASSERTION
+
+;; (canonical-local-host String)
+(struct canonical-local-host (name port) #:prefab) ;; ASSERTION
diff --git a/racketmq/server.rkt b/racketmq/server.rkt
index 5a27659..e3a5d4b 100644
--- a/racketmq/server.rkt
+++ b/racketmq/server.rkt
@@ -21,107 +21,26 @@
 (require syndicate/functional-queue)
 
 (require "private/util.rkt")
+(require "protocol.rkt")
+(require "config.rkt")
 
-(module+ test (require rackunit))
+(define (vh host-name port) (web-virtual-host "http" host-name port))
 
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-
-;; TODO: sane defaults
-(define *max-upstream-redirects* 5)
-(define *server-port* 7827)
-(define *canonical-host* "localhost")
-(define *accepted-hosts* (list *canonical-host*))
-(define *min-poll-interval* 10) ;; seconds
-(define *default-lease* "unbounded")
-(define *default-poll-interval* "none")
-(define *max-dead-letters* 10)
-(define *max-delivery-retries* 10)
-(define *initial-retry-delay* 5.0) ;; seconds
-(define *retry-delay-multiplier* 1.618)
-(define *max-retry-delay* 30) ;; seconds
-
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-
-;; A Topic is a URIString.
-
-;; A Deadline is an (Option Number), where #f indicates "unbounded",
-;; and numbers indicate a moment in time as a Unix epoch timestamp as
-;; might be returned from `current-seconds`.
-
-;; A Notification contains both `topic-name`, indicating the *local*
-;; name for the topic that is being subscribed to, as well as
-;; `canonical-topic`, which is the rel=self URL given by the upstream
-;; topic itself. The former is our local key for finding resources;
-;; the latter is a property of the topic content, not a property of
-;; the subscription. The same is true of `canonical-hub`: it pertains
-;; to the topic, not the subscription. The `topic-name` is the only
-;; field pertaining to a subscription; all the others pertain to the
-;; content.
-(struct notification (topic-name ;; Topic
-                      canonical-hub ;; Option URLString
-                      canonical-topic ;; Option Topic
-                      content ;; Bytes
-                      content-type) ;; Option String
-  #:prefab)
-
-;; (update-subscription Topic URLString (Option SubscriptionSettings))
-(struct update-subscription (topic callback settings) #:prefab) ;; message
-
-;; (subscription Topic URLString SubscriptionSettings)
-(struct subscription (topic callback settings-) #:prefab) ;; assertion
-
-(struct subscription-settings (expiry-deadline ;; Deadline
-                               secret ;; Option Bytes
-                               poll-interval-seconds) ;; Option Number
-  #:prefab)
-
-;; (local-topic-config Topic (Option Number) (Option Number))
-(struct local-topic-config (name max-age max-count) #:prefab)
-
-;; (topic-demand Topic (Option Number))
-(struct topic-demand (topic-name poll-interval-seconds) #:prefab)
-
-;; (local-topic-demand String)
-(struct local-topic-demand (name) #:prefab)
-
-;; (local-host String)
-(struct local-host (name) #:prefab)
-
-;; (canonical-local-host String)
-(struct canonical-local-host (name) #:prefab)
-
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-
-;; (define (number->path n)
-;;   (let ((top (quotient n 256))
-;;         (bot (remainder n 256)))
-;;     (define bot-piece (~r bot #:base 16 #:min-width 2 #:pad-string "0"))
-;;     (if (zero? top)
-;;         bot-piece
-;;         (string-append (number->path top) "-/" bot-piece))))
-
-;; (module+ test
-;;   (check-equal? (number->path 0) "00")
-;;   (check-equal? (number->path 123) "7b")
-;;   (check-equal? (number->path 12345) "30-/39")
-;;   (check-equal? (number->path 123456789012345678901234567890)
-;;                 "01-/8e-/e9-/0f-/f6-/c3-/73-/e0-/ee-/4e-/3f-/0a-/d2"))
-
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-
-(define (vh host-name) (web-virtual-host "http" host-name *server-port*))
+(spawn-configuration "defaults.rktd")
 
 (actor #:name 'main
 
-       (for [(h *accepted-hosts*)]
-         (assert (local-host h)))
+       (during (config (list 'canonical-host $h $p))
+         (assert (canonical-local-host h p))
+         (assert (local-host h p)))
 
-       (assert (canonical-local-host *canonical-host*))
+       (during (config (list 'accepted-host $h $p))
+         (assert (local-host h p)))
 
-       (during (local-host $host-name)
-         (assert (vh host-name))
+       (during (local-host $host-name $port)
+         (assert (vh host-name port))
 
-         (on (web-request-get (id req) (vh host-name) ("" ()))
+         (on (web-request-get (id req) (vh host-name port) ("" ()))
              (actor*
               (web-respond/xexpr! id
                                   `(html
@@ -138,8 +57,8 @@
 
 (actor #:name 'static-content-server
        (define url->path (make-url->path htdocs-path))
-       (during (local-host $host-name)
-         (on (web-request-get (id req) (vh host-name) ,_)
+       (during (local-host $host-name $port)
+         (on (web-request-get (id req) (vh host-name port) ,_)
              (define-values (path path-pieces)
                (url->path (resource->url (web-request-header-resource req))))
              (when (file-exists? path)
@@ -151,8 +70,8 @@
 
        (field [topics (set)])
 
-       (during (local-host $host-name)
-         (on (web-request-incoming (id req) (vh host-name) 'put ("topic" (,$topic ())))
+       (during (local-host $host-name $port)
+         (on (web-request-incoming (id req) (vh host-name port) 'put ("topic" (,$topic ())))
              (when (not (set-member? (topics) topic))
                (topics (set-add (topics) topic))
                (assert! (local-topic-demand topic))
@@ -160,7 +79,7 @@
                (assert! (local-topic-config topic #f #f))) ;; TODO: maximums
              (web-respond/bytes! id #""))
 
-         (on (web-request-incoming (id req) (vh host-name) 'delete ("topic" (,$topic ())))
+         (on (web-request-incoming (id req) (vh host-name port) 'delete ("topic" (,$topic ())))
              (when (set-member? (topics) topic)
                (topics (set-remove (topics) topic))
                (retract! (local-topic-demand topic))
@@ -172,28 +91,32 @@
          (local-topic-main topic)))
 
 (actor #:name 'topic-demand-analyzer
-       (define/query-set local-hosts (local-host $host-name) host-name)
+       (define/query-set local-hosts ($ h (local-host _ _)) h)
        (during/actor (topic-demand $full-topic _)
          #:name (list 'general-topic full-topic)
          #:let [(local-hosts-snapshot (local-hosts))]
          (with-handlers [(exn? (lambda (e)
                                  (log-error "Topic demand error: ~a" (exn->string e))))]
-           (match-define (web-resource (web-virtual-host _ topic-host _) topic-path)
+           (match-define (web-resource (web-virtual-host _ topic-host topic-port) topic-path)
              (url->resource (string->url full-topic)))
            (define maybe-local-topic
              (match topic-path [`("topic" (,topic ())) topic] [_ #f]))
            (general-topic-main full-topic
                                topic-host
+                               topic-port
                                maybe-local-topic
-                               (set-member? local-hosts-snapshot topic-host)))))
+                               (set-member? local-hosts-snapshot
+                                            (local-host topic-host topic-port))))))
 
-(define (general-topic-main full-topic topic-host maybe-local-topic start-as-local?)
+(define (general-topic-main full-topic topic-host topic-port maybe-local-topic start-as-local?)
   (define (local-state)
-    (react (stop-when (retracted (local-host topic-host)) (remote-state))
+    (react (stop-when (retracted (local-host topic-host topic-port))
+                      (remote-state))
            (assert (local-topic-demand maybe-local-topic))))
 
   (define (remote-state)
-    (react (stop-when #:when maybe-local-topic (asserted (local-host topic-host)) (local-state))
+    (react (stop-when #:when maybe-local-topic (asserted (local-host topic-host topic-port))
+                      (local-state))
            (remote-topic-main full-topic)))
 
   (on-start
@@ -204,8 +127,8 @@
 (define (req-content-type req)
   (dict-ref (web-request-header-headers req) 'content-type #f))
 
-(define (canonical-url canonical-host-name path)
-  (url->string (resource->url (web-resource (vh canonical-host-name) path))))
+(define (canonical-url canonical-host-name cport path)
+  (url->string (resource->url (web-resource (vh canonical-host-name cport) path))))
 
 (define (local-topic-main topic)
   (field [max-age #f]
@@ -227,10 +150,10 @@
               (max-count)))
   (on-stop (log-info "Terminating local topic ~v" topic))
 
-  (during (local-host $host-name)
-    (during (canonical-local-host $canonical-host-name)
-      (define hub-url (canonical-url canonical-host-name `("hub" ())))
-      (define self-url (canonical-url canonical-host-name `("topic" (,topic ()))))
+  (during (local-host $host-name $port)
+    (during (canonical-local-host $canonical-host-name $cport)
+      (define hub-url (canonical-url canonical-host-name cport `("hub" ())))
+      (define self-url (canonical-url canonical-host-name cport `("topic" (,topic ()))))
       (define discovery-headers (list (cons 'link (format "<~a>; rel=hub" hub-url))
                                       (cons 'link (format "<~a>; rel=self" self-url))))
 
@@ -252,11 +175,11 @@
                                           #:headers discovery-headers)
                                 #""))) ;; MUST NOT include a response body for 204
 
-      (on (web-request-incoming (id req) (vh host-name) 'head ("topic" (,topic ())))
+      (on (web-request-incoming (id req) (vh host-name port) 'head ("topic" (,topic ())))
           (topic-response id #f))
-      (on (web-request-get (id req) (vh host-name) ("topic" (,topic ())))
+      (on (web-request-get (id req) (vh host-name port) ("topic" (,topic ())))
           (topic-response id #t))
-      (on (web-request-incoming (id req) (vh host-name) 'post ("topic" (,topic ())) $body)
+      (on (web-request-incoming (id req) (vh host-name port) 'post ("topic" (,topic ())) $body)
           (define content-type (req-content-type req))
           (log-info "Local topic ~a got ~v message ~v" topic content-type body)
           (current-content body)
@@ -283,12 +206,13 @@
          [poll-interval-seconds #f])
 
   (define/query-set poll-intervals (topic-demand full-topic $i) i)
+  (define/query-config min-poll-interval 60)
   (begin/dataflow
     (define candidate (for/fold [(i #f)] [(candidate (in-set (poll-intervals)))]
                         (cond [(not i) candidate]
                               [(< candidate i) candidate]
                               [else i])))
-    (poll-interval-seconds (and candidate (max candidate *min-poll-interval*))))
+    (poll-interval-seconds (and candidate (max candidate (min-poll-interval)))))
   (begin/dataflow
     (log-info "Poll interval for ~a is now ~a"
               full-topic
@@ -296,8 +220,8 @@
                 [#f "disabled"]
                 [n (format "~a seconds" n)])))
 
-  (during (canonical-local-host $canonical-host-name)
-    (define callback (canonical-url canonical-host-name `("sub" (,sub-id ()))))
+  (during (canonical-local-host $canonical-host-name $cport)
+    (define callback (canonical-url canonical-host-name cport `("sub" (,sub-id ()))))
 
     (define (refresh-subscription!)
       ;; TODO: shared secret
@@ -326,10 +250,12 @@
         (unsubscribe!)
         (refresh-subscription!)))
 
+    (define/query-config max-upstream-redirects 5)
+
     (on (asserted (later-than (+ (last-upstream-check) (* 1000 (or (poll-interval-seconds) 0)))))
         (log-info "Checking upstream ~a" full-topic)
         (define-values (resp response-body)
-          (web-request! 'get full-topic #:redirect-budget *max-upstream-redirects*))
+          (web-request! 'get full-topic #:redirect-budget (max-upstream-redirects)))
         (last-upstream-check (current-inexact-milliseconds))
         (match (web-response-header-code-type resp)
           ['successful
@@ -356,12 +282,12 @@
                         other
                         (web-response-header-code resp))]))
 
-    (on (web-request-get (id req) (vh canonical-host-name) ("sub" (,sub-id ())))
+    (on (web-request-get (id req) (vh canonical-host-name cport) ("sub" (,sub-id ())))
         (define challenge (dict-ref (web-request-header-query req) 'hub.challenge ""))
         (log-info "Received verification-of-intent: ~v" (web-request-header-query req))
         (web-respond/bytes! id (string->bytes/utf-8 challenge)))
 
-    (on (web-request-incoming (id req) (vh canonical-host-name) 'post ("sub" (,sub-id ())) $body)
+    (on (web-request-incoming (id req) (vh canonical-host-name cport) 'post ("sub" (,sub-id ())) $body)
         ;; TODO: verify the use of the shared secret
         (actor*
          (define parsed-link-headers (parse-link-headers (web-request-header-headers req)))
@@ -385,10 +311,10 @@
          (web-respond/status! id 201 #"Created")))))
 
 (actor #:name 'hub
-       (during (local-host $host-name)
-         (during (canonical-local-host $canonical-host-name)
-           (on (web-request-incoming (id req) (vh host-name) 'post ("hub" ()) $body)
-               (asynchronous-verification-of-intent id req body canonical-host-name)
+       (during (local-host $host-name $port)
+         (during (canonical-local-host $canonical-host-name $cport)
+           (on (web-request-incoming (id req) (vh host-name port) 'post ("hub" ()) $body)
+               (asynchronous-verification-of-intent id req body canonical-host-name cport)
                (web-respond/status! id 202 #"Accepted"))))
 
        (on (message (update-subscription $topic $callback $settings))
@@ -400,7 +326,7 @@
          #:on-crash (retract! (subscription topic callback ?))
          (subscription-main topic callback)))
 
-(define (asynchronous-verification-of-intent id req body canonical-host-name)
+(define (asynchronous-verification-of-intent id req body canonical-host-name cport)
   (actor* (define params (make-immutable-hash (form-urlencoded->alist (bytes->string/utf-8 body))))
           (define callback (hash-ref params 'hub.callback))
           (define mode (match (hash-ref params 'hub.mode)
@@ -410,13 +336,18 @@
           (define topic
             (url->string
              (combine-url/relative (string->url (canonical-url canonical-host-name
+                                                               cport
                                                                `("topic" ("" ()))))
                                    requested-topic)))
-          (define lease-seconds (match (hash-ref params 'hub.lease_seconds *default-lease*)
+          (define lease-seconds (match (hash-ref params
+                                                 'hub.lease_seconds
+                                                 (config-ref 'default-lease 86400))
                                   ["unbounded" #f]
                                   [n (string->number n)]))
           (define poll-interval-seconds
-            (match (hash-ref params 'hub.poll_interval_seconds *default-poll-interval*)
+            (match (hash-ref params
+                             'hub.poll_interval_seconds
+                             (config-ref 'default-poll-interval "none"))
               ["none" #f]
               [n (string->number n)]))
           (define secret-string (hash-ref params 'hub.secret #f))
@@ -464,19 +395,25 @@
          [message-queue (make-queue)]
          [dead-letters (make-queue)])
 
-  (stop-when (rising-edge (> (queue-length (dead-letters)) *max-dead-letters*))
+  (define/query-config max-dead-letters 10)
+  (define/query-config initial-retry-delay 5.0)
+  (define/query-config max-delivery-retries 10)
+  (define/query-config retry-delay-multiplier 1.618)
+  (define/query-config max-retry-delay 30)
+
+  (stop-when (rising-edge (> (queue-length (dead-letters)) (max-dead-letters)))
              (log-info "Too many dead letters for ~a" callback))
 
   (define (deliver-queued-notifications)
     (delivery-active? #t)
-    (let deliver-rest ((retry-delay *initial-retry-delay*))
+    (let deliver-rest ((retry-delay (initial-retry-delay)))
       (when (not (queue-empty? (message-queue)))
         (define-values (n newq) (dequeue (message-queue)))
         (message-queue newq)
         (match-define (notification _ canonical-hub canonical-topic body content-type) n)
         (define link-headers (append (maybe-link-header canonical-hub 'hub)
                                      (maybe-link-header canonical-topic 'self)))
-        (let deliver-one ((retries-remaining *max-delivery-retries*)
+        (let deliver-one ((retries-remaining (max-delivery-retries))
                           (retry-delay retry-delay))
           (define-values (resp _body)
             (web-request! 'post
@@ -487,7 +424,7 @@
                           #:body body))
           (cond
             [(eq? (web-response-header-code-type resp) 'successful)
-             (deliver-rest *initial-retry-delay*)]
+             (deliver-rest (initial-retry-delay))]
             [(zero? retries-remaining)
              (log-info "Dead letter for ~v" callback)
              (dead-letters (enqueue (dead-letters) n))
@@ -501,8 +438,8 @@
               resp)
              (sleep retry-delay)
              (deliver-one (- retries-remaining 1)
-                          (min (* retry-delay *retry-delay-multiplier*)
-                               *max-retry-delay*))]))))
+                          (min (* retry-delay (retry-delay-multiplier))
+                               (max-retry-delay)))]))))
     (delivery-active? #f))
 
   (during (subscription topic callback (subscription-settings