From fc99afcd6a15803782ba42020a2e52ed89e3df7e Mon Sep 17 00:00:00 2001
From: Sam Tobin-Hochstadt <samth@iu.edu>
Date: Thu, 22 Jan 2026 13:08:36 -0500
Subject: [PATCH] Fix intermittent universe-restart.rkt DrDr failure

Handle network errors in broadcast when universe drops a world.

Example: https://drdr.racket-lang.org/71877/racket/share/pkgs/htdp-test/2htdp/tests/universe-restart.rkt
---
 htdp-lib/2htdp/private/world.rkt | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/htdp-lib/2htdp/private/world.rkt b/htdp-lib/2htdp/private/world.rkt
index 28222173..b693a52a 100644
--- a/htdp-lib/2htdp/private/world.rkt
+++ b/htdp-lib/2htdp/private/world.rkt
@@ -132,9 +132,10 @@
               (thread (RECEIVE in))))))
       
       (define/private (broadcast msg)
-        (when *out* 
+        (when *out*
           (check-result 'send sexp? "Sexp expected; given ~e\n" msg)
-          (tcp-send *out* msg)))
+          (with-handlers ([exn:fail:network? (lambda (e) (set! *out* #f))])
+            (tcp-send *out* msg))))
       
       ;; -----------------------------------------------------------------------
       (field