Fix test_u_async_comprehensive: add Windows socketpair replacement using UDP sockets

tests/test_u_async_comprehensive.c

@@ -384,7 +384,28 @@ static void test_concurrent_operations(void) {
     /* Create socket pair for testing */
     int sockets[2];
     void* socket_ids[2];
+#ifdef _WIN32
+    // Windows doesn't have socketpair, use UDP sockets instead
+    sockets[0] = socket(AF_INET, SOCK_DGRAM, 0);
+    sockets[1] = socket(AF_INET, SOCK_DGRAM, 0);
+    ASSERT_TRUE(sockets[0] >= 0 && sockets[1] >= 0, "Failed to create sockets");
+    
+    struct sockaddr_in addr1, addr2;
+    memset(&addr1, 0, sizeof(addr1));
+    addr1.sin_family = AF_INET;
+    addr1.sin_addr.s_addr = inet_addr("127.0.0.1");
+    addr1.sin_port = htons(0);  // Let system choose port
+    
+    memset(&addr2, 0, sizeof(addr2));
+    addr2.sin_family = AF_INET;
+    addr2.sin_addr.s_addr = inet_addr("127.0.0.1");
+    addr2.sin_port = htons(0);
+    
+    ASSERT_EQ(bind(sockets[0], (struct sockaddr*)&addr1, sizeof(addr1)), 0, "Failed to bind socket 0");
+    ASSERT_EQ(bind(sockets[1], (struct sockaddr*)&addr2, sizeof(addr2)), 0, "Failed to bind socket 1");
+#else
     ASSERT_EQ(socketpair(AF_UNIX, SOCK_DGRAM, 0, sockets), 0, "Failed to create socket pair");
+#endif
     
     /* Make non-blocking */
     for (int i = 0; i < 2; i++) {