+#include <sys/types.h>
+#if (defined(VMS) || defined(__VMS)) && !defined(FD_SET)
+/* VAX C does not defined fd_set and friends, but it's actually quite simple */
+/* These definitions are borrowed from SOCKETSHR. /Richard Levitte */
+#define MAX_NOFILE 32
+#define NBBY 8 /* number of bits in a byte */
+
+#ifndef FD_SETSIZE
+#define FD_SETSIZE MAX_NOFILE
+#endif /* FD_SETSIZE */
+
+/* How many things we'll allow select to use. 0 if unlimited */
+#define MAXSELFD MAX_NOFILE
+typedef int fd_mask; /* int here! VMS prototypes int, not long */
+#define NFDBITS (sizeof(fd_mask) * NBBY) /* bits per mask (power of 2!)*/
+#define NFDSHIFT 5 /* Shift based on above */
+
+typedef fd_mask fd_set;
+#define FD_SET(n, p) (*(p) |= (1 << ((n) % NFDBITS)))
+#define FD_CLR(n, p) (*(p) &= ~(1 << ((n) % NFDBITS)))
+#define FD_ISSET(n, p) (*(p) & (1 << ((n) % NFDBITS)))
+#define FD_ZERO(p) memset((char *)(p), 0, sizeof(*(p)))
+#endif
+