From a3725374ca3a38fd80d10bdab92e5f36f2f18854 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sat, 17 Jun 2017 07:35:09 -0600
Subject: [PATCH] rktio: repair for UDP disconnect

---
 racket/src/racket/src/network.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/racket/src/racket/src/network.c b/racket/src/racket/src/network.c
index ade238836f..85ea0a74de 100644
--- a/racket/src/racket/src/network.c
+++ b/racket/src/racket/src/network.c
@@ -1893,13 +1893,15 @@ static Scheme_Object *udp_bind_or_connect(const char *name, int argc, Scheme_Obj
 
     if (SCHEME_FALSEP(argv[1]) && SCHEME_FALSEP(argv[2])) {
       /* DISCONNECT */
-      if (!rktio_udp_disconnect(scheme_rktio, udp->s)) {
-        scheme_raise_exn(MZEXN_FAIL_NETWORK, 
-                         "%s: can't disconnect\n"
-                         "  system error: %R",
-                         name);
+      if (udp->connected) {
+        if (!rktio_udp_disconnect(scheme_rktio, udp->s)) {
+          scheme_raise_exn(MZEXN_FAIL_NETWORK,
+                           "%s: can't disconnect\n"
+                           "  system error: %R",
+                           name);
+        }
+        udp->connected = 0;
       }
-      udp->connected = 0;
       return scheme_void;
     }