diff --git a/esp32/main/spectfd.c b/esp32/main/spectfd.c
index fae60d6a..1f8dac3b 100644
--- a/esp32/main/spectfd.c
+++ b/esp32/main/spectfd.c
@@ -1,8 +1,10 @@
 #include "spectfd.h"
 #include <string.h>
 #include <unistd.h>
+#include <stdbool.h>
 
 #define MAX_SPECT_FD 16
+#define SPECTFD_RESERVED (0)
 
 static int spectfd_map[MAX_SPECT_FD];
 
@@ -11,11 +13,21 @@ void spectfd__init(void)
     memset(spectfd_map, 0xFF, sizeof(spectfd_map));
 }
 
+static bool spectfd__is_valid_system(int index)
+{
+    return (spectfd_map[index]>SPECTFD_RESERVED);
+}
+
+static bool spectfd__is_valid_system_or_reserved(int index)
+{
+    return (spectfd_map[index]>SPECTFD_RESERVED);
+}
+
 void spectfd__close_all(void)
 {
     unsigned i;
     for (i=0;i<MAX_SPECT_FD;i++) {
-        if (spectfd_map[i]<0)
+        if (!spectfd__is_valid_system(i))
             continue;
         close(spectfd_map[i]);
         spectfd_map[i] = SPECTFD_ERROR;
@@ -34,11 +46,33 @@ spectfd_t spectfd__alloc(int systemfd)
 {
     unsigned i;
     for (i=0;i<MAX_SPECT_FD;i++) {
-        if (spectfd_map[i]<0) {
+        if (spectfd__is_valid_system_or_reserved(i)) {
             continue;
         }
-        spectfd_map[i] =  systemfd;
+        spectfd_map[i] = systemfd;
         return i;
     }
     return SPECTFD_ERROR;
 }
+
+spectfd_t spectfd__prealloc()
+{
+    return spectfd__alloc( SPECTFD_RESERVED );
+}
+
+void spectfd__update_systemfd(spectfd_t fd, int systemfd)
+{
+    spectfd_map[fd] = systemfd;
+}
+
+int spectfd__close(spectfd_t fd)
+{
+    int sysfd = spectfd_map[fd];
+    if (spectfd__is_valid_system(fd))
+        close(sysfd);
+
+    spectfd_map[fd] = SPECTFD_ERROR;
+    return 0;
+}
+
+
diff --git a/esp32/main/spectfd.h b/esp32/main/spectfd.h
index dc11109f..0e871b6b 100644
--- a/esp32/main/spectfd.h
+++ b/esp32/main/spectfd.h
@@ -2,7 +2,6 @@
 #define __SPECTFD_H__
 
 #include <inttypes.h>
-
 /**
  * \defgrou Spectrum file descriptors
  * \ingroup misc
@@ -16,5 +15,8 @@ void spectfd__init(void);
 void spectfd__close_all(void);
 int spectfd__spect_to_system(spectfd_t fd);
 spectfd_t spectfd__alloc(int systemfd);
+spectfd_t spectfd__prealloc();
+void spectfd__update_systemfd(spectfd_t fd, int systemfd);
+int spectfd__close(spectfd_t fd);
 
 #endif