From 3244bb931b48ebfa0ce6634549e1fdf869d218bb Mon Sep 17 00:00:00 2001
From: Samuel Williams <samuel.williams@oriontransfer.co.nz>
Date: Fri, 12 Apr 2024 23:22:50 +1200
Subject: [PATCH] Check for availability of `MSG_DONTWAIT`.

---
 ext/socket/basicsocket.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/ext/socket/basicsocket.c b/ext/socket/basicsocket.c
index 1b18077d61..d9afb5b981 100644
--- a/ext/socket/basicsocket.c
+++ b/ext/socket/basicsocket.c
@@ -745,7 +745,12 @@ bsock_readable_p(VALUE self)
         RB_IO_POINTER(self, fptr);
 
         char buffer[1];
+#ifdef MSG_DONTWAIT
         int result = recv(fptr->fd, buffer, 1, MSG_PEEK | MSG_DONTWAIT);
+#else
+        rb_io_set_nonblock(fptr);
+        int result = recv(fptr->fd, buffer, 1, MSG_PEEK);
+#endif
 
         if (result > 0) {
             return Qtrue;