diff --git a/repl-server.rkt b/repl-server.rkt
index 3455512..75842c3 100644
--- a/repl-server.rkt
+++ b/repl-server.rkt
@@ -17,6 +17,8 @@
 
 (define *user-states* (make-hash))
 
+(define *login-limit* (make-semaphore 3))
+
 (define *interaction* (make-room 'interaction))
 (spy-on *interaction*)
 
@@ -120,9 +122,23 @@
     (close-input-port in)
     (close-output-port out)))
 
+(define (limited-repl-shell username in out)
+  (call-with-semaphore *login-limit*
+		       (lambda () (repl-shell username in out))
+		       (lambda () (reject-login username in out))))
+
+(define (reject-login username in out)
+  (parameterize ((current-input-port in)
+		 (current-output-port out)
+		 (current-error-port out))
+    (printf "Hello, ~a - unfortunately, the system is too busy to accept your\n" username)
+    (printf "login right now. Please try again later.\n")
+    (close-input-port in)
+    (close-output-port out)))
+
 (define (t-server)
   (define s (tcp-listen 2322 4 #t))
   (printf "Accepting...\n")
-  (tcp-pty-ssh-server s repl-shell #:prompt *prompt*))
+  (tcp-pty-ssh-server s limited-repl-shell #:prompt *prompt*))
 
 (t-server)