diff --git a/src/vcl/ldp.c b/src/vcl/ldp.c
index e7a80cb..d31cd2c 100644
--- a/src/vcl/ldp.c
+++ b/src/vcl/ldp.c
@@ -796,6 +796,34 @@
       return -1;
     }
 
+  if (timeout)
+    {
+      time_out = (timeout->tv_sec == 0 && timeout->tv_nsec == 0) ?
+	(f64) 0 : (f64) timeout->tv_sec +
+	(f64) timeout->tv_nsec / (f64) 1000000000;
+
+      /* select as fine grained sleep */
+      if (!nfds)
+	{
+	  if (LDP_DEBUG > 3)
+	    clib_warning ("LDP<%d>: sleeping for %.02f seconds",
+			  getpid (), time_out);
+
+	  time_out += clib_time_now (&ldp->clib_time);
+	  while (clib_time_now (&ldp->clib_time) < time_out)
+	    ;
+	  return 0;
+	}
+    }
+  else if (!nfds)
+    {
+      errno = EINVAL;
+      return -1;
+    }
+  else
+    time_out = -1;
+
+
   if (nfds <= ldp->sid_bit_val)
     {
       func_str = "libc_pselect";
@@ -821,34 +849,6 @@
       return -1;
     }
 
-  if (timeout)
-    {
-      time_out = (timeout->tv_sec == 0 && timeout->tv_nsec == 0) ?
-	(f64) 0 : (f64) timeout->tv_sec +
-	(f64) timeout->tv_nsec / (f64) 1000000000 +
-	(f64) (timeout->tv_nsec % 1000000000) / (f64) 1000000000;
-
-      /* select as fine grained sleep */
-      if (!nfds)
-	{
-	  if (LDP_DEBUG > 3)
-	    clib_warning ("LDP<%d>: sleeping for %f seconds",
-			  getpid (), time_out);
-
-	  time_out += clib_time_now (&ldp->clib_time);
-	  while (clib_time_now (&ldp->clib_time) < time_out)
-	    ;
-	  return 0;
-	}
-    }
-  else if (!nfds)
-    {
-      errno = EINVAL;
-      return -1;
-    }
-  else
-    time_out = -1;
-
   sid_bits = libc_bits = 0;
   if (readfds)
     {
@@ -3014,13 +3014,18 @@
   if ((errno = -ldp_init ()))
     return -1;
 
-  if (vep_idx != INVALID_SESSION_ID)
+  if (PREDICT_TRUE (vep_idx != INVALID_SESSION_ID))
     {
       u32 sid = ldp_sid_from_fd (fd);
 
+      if (LDP_DEBUG > 1)
+	clib_warning ("LDP<%d>: epfd %d (0x%x), vep_idx %d (0x%x), "
+		      "sid %d (0x%x)", getpid (), epfd, epfd,
+		      vep_idx, vep_idx, sid, sid);
+
       if (sid != INVALID_SESSION_ID)
 	{
-	  func_str = "vppcom_epoll_create";
+	  func_str = "vppcom_epoll_ctl";
 
 	  if (LDP_DEBUG > 1)
 	    clib_warning ("LDP<%d>: epfd %d (0x%x): calling %s(): "
@@ -3037,30 +3042,45 @@
 	}
       else
 	{
-	  int epfd;
+	  int libc_epfd;
 	  u32 size = sizeof (epfd);
 
 	  func_str = "vppcom_session_attr[GET_LIBC_EPFD]";
-	  epfd = vppcom_session_attr (vep_idx, VPPCOM_ATTR_GET_LIBC_EPFD,
-				      0, 0);
-	  if (!epfd)
+	  libc_epfd = vppcom_session_attr (vep_idx,
+					   VPPCOM_ATTR_GET_LIBC_EPFD, 0, 0);
+	  if (LDP_DEBUG > 1)
+	    clib_warning ("LDP<%d>: epfd %d (0x%x), vep_idx %d (0x%x): "
+			  "%s() returned libc_epfd %d (0x%x)",
+			  getpid (), epfd, epfd, vep_idx, vep_idx,
+			  func_str, libc_epfd, libc_epfd);
+
+	  if (!libc_epfd)
 	    {
 	      func_str = "libc_epoll_create1";
 
 	      if (LDP_DEBUG > 1)
-		clib_warning ("LDP<%d>: calling %s(): EPOLL_CLOEXEC",
-			      getpid (), func_str);
+		clib_warning ("LDP<%d>: epfd %d (0x%x), vep_idx %d (0x%x): "
+			      "calling %s(): EPOLL_CLOEXEC",
+			      getpid (), epfd, epfd, vep_idx, vep_idx,
+			      func_str);
 
-	      epfd = libc_epoll_create1 (EPOLL_CLOEXEC);
-	      if (epfd < 0)
+	      libc_epfd = libc_epoll_create1 (EPOLL_CLOEXEC);
+	      if (libc_epfd < 0)
 		{
-		  rv = epfd;
+		  rv = libc_epfd;
 		  goto done;
 		}
 
 	      func_str = "vppcom_session_attr[SET_LIBC_EPFD]";
+	      if (LDP_DEBUG > 1)
+		clib_warning ("LDP<%d>: epfd %d (0x%x): calling %s(): "
+			      "vep_idx %d (0x%x), VPPCOM_ATTR_SET_LIBC_EPFD, "
+			      "libc_epfd %d (0x%x), size %d",
+			      getpid (), epfd, epfd, func_str,
+			      vep_idx, vep_idx, libc_epfd, libc_epfd, size);
+
 	      rv = vppcom_session_attr (vep_idx, VPPCOM_ATTR_SET_LIBC_EPFD,
-					&epfd, &size);
+					&libc_epfd, &size);
 	      if (rv < 0)
 		{
 		  errno = -rv;
@@ -3068,18 +3088,32 @@
 		  goto done;
 		}
 	    }
-	  else if (PREDICT_FALSE (epfd < 0))
+	  else if (PREDICT_FALSE (libc_epfd < 0))
 	    {
 	      errno = -epfd;
 	      rv = -1;
 	      goto done;
 	    }
 
-	  rv = libc_epoll_ctl (epfd, op, fd, event);
+	  func_str = "libc_epoll_ctl";
+
+	  if (LDP_DEBUG > 1)
+	    clib_warning ("LDP<%d>: epfd %d (0x%x): calling %s(): "
+			  "libc_epfd %d (0x%x), op %d, "
+			  "fd %d (0x%x), event %p",
+			  getpid (), epfd, epfd, func_str,
+			  libc_epfd, libc_epfd, op, fd, fd, event);
+
+	  rv = libc_epoll_ctl (libc_epfd, op, fd, event);
 	}
     }
   else
     {
+      /* The LDP epoll_create1 always creates VCL epfd's.
+       * The app should never have a kernel base epoll fd unless it
+       * was acquired outside of the LD_PRELOAD process context.
+       * In any case, if we get one, punt it to libc_epoll_ctl.
+       */
       func_str = "libc_epoll_ctl";
 
       if (LDP_DEBUG > 1)
@@ -3152,9 +3186,10 @@
   if (LDP_DEBUG > 2)
     clib_warning ("LDP<%d>: epfd %d (0x%x): vep_idx %d (0x%x), "
 		  "libc_epfd %d (0x%x), events %p, maxevents %d, "
-		  "timeout %d, sigmask %p", getpid (), epfd, epfd,
-		  vep_idx, vep_idx, libc_epfd, libc_epfd, events,
-		  maxevents, timeout, sigmask);
+		  "timeout %d, sigmask %p: time_to_wait %.02f",
+		  getpid (), epfd, epfd, vep_idx, vep_idx,
+		  libc_epfd, libc_epfd, events, maxevents, timeout,
+		  sigmask, time_to_wait, time_out);
   do
     {
       if (!ldp->epoll_wait_vcl)
diff --git a/src/vcl/sock_test.h b/src/vcl/sock_test.h
index b4a22ad..0729c31 100644
--- a/src/vcl/sock_test.h
+++ b/src/vcl/sock_test.h
@@ -48,6 +48,11 @@
 #define SOCK_TEST_CFG_BUF_SIZE_MIN    128
 #define SOCK_TEST_CFG_MAX_TEST_SCKTS  5
 
+#define SOCK_TEST_AF_UNIX_FILENAME    "/tmp/ldp_server_af_unix_socket"
+#define SOCK_TEST_MIXED_EPOLL_DATA    "Hello, world! (over an AF_UNIX socket)"
+#define SOCK_TEST_AF_UNIX_ACCEPT_DATA 0xaf0000af
+#define SOCK_TEST_AF_UNIX_FD_MASK     0x00af0000
+
 typedef enum
 {
   SOCK_TEST_TYPE_NONE,
@@ -302,6 +307,13 @@
             stats->stop.tv_sec, stats->stop.tv_nsec);
             
   printf (SOCK_TEST_SEPARATOR_STRING);
+  
+#if SOCK_SERVER_USE_EPOLL && !defined (VCL_TEST)
+  printf ("  af_unix xacts:  %lu (0x%08lx)\n",
+          sock_server_main.af_unix_xacts);
+          
+  printf (SOCK_TEST_SEPARATOR_STRING);
+#endif
 }
 
 static inline int
diff --git a/src/vcl/sock_test_client.c b/src/vcl/sock_test_client.c
index ddb9e7f..7a735f5 100644
--- a/src/vcl/sock_test_client.c
+++ b/src/vcl/sock_test_client.c
@@ -23,11 +23,17 @@
 #include <time.h>
 #include <arpa/inet.h>
 #include <vcl/sock_test.h>
+#ifndef VCL_TEST
+#include <sys/un.h>
+#endif
 
 typedef struct
 {
 #ifdef VCL_TEST
   vppcom_endpt_t server_endpt;
+#else
+  int af_unix_echo_tx;
+  int af_unix_echo_rx;
 #endif
   struct sockaddr_in server_addr;
   sock_test_socket_t ctrl_socket;
@@ -201,6 +207,94 @@
     }
   clock_gettime (CLOCK_REALTIME, &ctrl->stats.stop);
 
+#ifndef VCL_TEST
+  {
+    int fd, errno_val;
+    struct sockaddr_un serveraddr;
+    uint8_t buffer[256];
+    size_t nbytes = strlen (SOCK_TEST_MIXED_EPOLL_DATA) + 1;
+    struct timeval timeout;
+
+    /* Open AF_UNIX socket and send an echo to test mixed epoll on server.
+     */
+    fd = socket (AF_UNIX, SOCK_STREAM, 0);
+    if (fd < 0)
+      {
+	errno_val = errno;
+	perror ("ERROR in echo_test_client(): socket(AF_UNIX) failed");
+	fprintf (stderr,
+		 "CLIENT: ERROR: socket(AF_UNIX, SOCK_STREAM, 0) failed "
+		 "(errno = %d)!\n", errno_val);
+	goto out;
+      }
+    memset (&serveraddr, 0, sizeof (serveraddr));
+    serveraddr.sun_family = AF_UNIX;
+    strcpy (serveraddr.sun_path, SOCK_TEST_AF_UNIX_FILENAME);
+    rv = connect (fd, (struct sockaddr *) &serveraddr, SUN_LEN (&serveraddr));
+    if (rv < 0)
+      {
+	errno_val = errno;
+	perror ("ERROR in echo_test_client(): connect() failed");
+	fprintf (stderr, "CLIENT: ERROR: connect(fd %d, \"%s\", %lu) "
+		 "failed (errno = %d)!\n", fd, SOCK_TEST_AF_UNIX_FILENAME,
+		 SUN_LEN (&serveraddr), errno_val);
+	goto done;
+      }
+
+    scm->af_unix_echo_tx++;
+    strcpy ((char *) buffer, SOCK_TEST_MIXED_EPOLL_DATA);
+    timeout.tv_sec = 0;
+    timeout.tv_usec = 250000;
+    select (0, NULL, NULL, NULL, &timeout);	/* delay .25 secs */
+    rv = write (fd, buffer, nbytes);
+    if (rv < 0)
+      {
+	errno_val = errno;
+	perror ("ERROR in echo_test_client(): write() failed");
+	fprintf (stderr, "CLIENT: ERROR: write(fd %d, \"%s\", %lu) "
+		 "failed (errno = %d)!\n", fd, buffer, nbytes, errno_val);
+	goto done;
+      }
+    else if (rv < nbytes)
+      {
+	fprintf (stderr, "CLIENT: ERROR: write(fd %d, \"%s\", %lu) "
+		 "returned %d!\n", fd, buffer, nbytes, rv);
+	goto done;
+      }
+
+    printf ("CLIENT (AF_UNIX): TX (%d bytes) - '%s'\n", rv, buffer);
+    memset (buffer, 0, sizeof (buffer));
+    rv = read (fd, buffer, nbytes);
+    if (rv < 0)
+      {
+	errno_val = errno;
+	perror ("ERROR in echo_test_client(): read() failed");
+	fprintf (stderr, "CLIENT: ERROR: read(fd %d, %p, %lu) "
+		 "failed (errno = %d)!\n", fd, buffer, nbytes, errno_val);
+	goto done;
+      }
+    else if (rv < nbytes)
+      {
+	fprintf (stderr, "CLIENT: ERROR: read(fd %d, %p, %lu) "
+		 "returned %d!\n", fd, buffer, nbytes, rv);
+	goto done;
+      }
+
+    if (!strncmp (SOCK_TEST_MIXED_EPOLL_DATA, (const char *) buffer, nbytes))
+      {
+	printf ("CLIENT (AF_UNIX): RX (%d bytes) - '%s'\n", rv, buffer);
+	scm->af_unix_echo_rx++;
+      }
+    else
+      printf ("CLIENT (AF_UNIX): ERROR: RX (%d bytes) - '%s'\n", rv, buffer);
+
+  done:
+    close (fd);
+  out:
+    ;
+  }
+#endif
+
   for (i = 0; i < ctrl->cfg.num_test_sockets; i++)
     {
       tsock = &scm->test_socket[i];
@@ -427,6 +521,10 @@
   sock_test_socket_t *tsock;
   int i;
 
+#ifndef VCL_TEST
+  printf ("CLIENT: af_unix_echo_tx %d, af_unix_echo_rx %d\n",
+	  scm->af_unix_echo_tx, scm->af_unix_echo_rx);
+#endif
   for (i = 0; i < ctrl->cfg.num_test_sockets; i++)
     {
       tsock = &scm->test_socket[i];
@@ -1085,10 +1183,11 @@
 #ifdef VCL_TEST
   vppcom_session_close (ctrl->fd);
   vppcom_app_destroy ();
+  return 0;
 #else
   close (ctrl->fd);
+  return (scm->af_unix_echo_tx == scm->af_unix_echo_rx) ? 0 : -1;
 #endif
-  return 0;
 }
 
 /*
diff --git a/src/vcl/sock_test_server.c b/src/vcl/sock_test_server.c
index 5476981..c0baefa 100644
--- a/src/vcl/sock_test_server.c
+++ b/src/vcl/sock_test_server.c
@@ -30,6 +30,9 @@
 
 #if SOCK_SERVER_USE_EPOLL
 #include <sys/epoll.h>
+#if !defined(VCL_TEST)
+#include <sys/un.h>
+#endif
 #endif
 
 #ifdef VCL_TEST
@@ -64,6 +67,13 @@
   int epfd;
   struct epoll_event listen_ev;
   struct epoll_event wait_events[SOCK_SERVER_MAX_EPOLL_EVENTS];
+#if !defined (VCL_TEST)
+  int af_unix_listen_fd;
+  int af_unix_fd;
+  struct epoll_event af_unix_listen_ev;
+  struct sockaddr_un serveraddr;
+  uint32_t af_unix_xacts;
+#endif
 #endif
   size_t num_conn;
   size_t conn_pool_size;
@@ -282,6 +292,75 @@
     }
 }
 
+#if SOCK_SERVER_USE_EPOLL && !defined (VCL_TEST)
+static inline void
+af_unix_echo (void)
+{
+  sock_server_main_t *ssm = &sock_server_main;
+  int af_unix_client_fd;
+  int rv;
+  int errno_val;
+  uint8_t buffer[256];
+  size_t nbytes = strlen (SOCK_TEST_MIXED_EPOLL_DATA) + 1;
+
+#if HAVE_ACCEPT4
+  af_unix_client_fd = accept4 (ssm->af_unix_listen_fd,
+			       (struct sockaddr *) NULL, NULL, NULL);
+#else
+  af_unix_client_fd = accept (ssm->af_unix_listen_fd,
+			      (struct sockaddr *) NULL, NULL);
+#endif
+  if (af_unix_client_fd < 0)
+    {
+      errno_val = errno;
+      perror ("ERROR in af_unix_accept()");
+      fprintf (stderr, "SERVER: ERROR: accept failed "
+	       "(errno = %d)!\n", errno_val);
+      return;
+    }
+
+  printf ("SERVER: Got an AF_UNIX connection -- fd = %d (0x%08x)!\n",
+	  af_unix_client_fd, af_unix_client_fd);
+
+  memset (buffer, 0, sizeof (buffer));
+
+  rv = read (af_unix_client_fd, buffer, nbytes);
+  if (rv < 0)
+    {
+      errno_val = errno;
+      perror ("ERROR in af_unix_echo(): read() failed");
+      fprintf (stderr, "SERVER: ERROR: read(af_unix_client_fd %d (0x%x), "
+	       "\"%s\", nbytes %lu) failed (errno = %d)!\n",
+	       af_unix_client_fd, af_unix_client_fd, buffer, nbytes,
+	       errno_val);
+      goto done;
+    }
+
+  printf ("SERVER (AF_UNIX): RX (%d bytes) - '%s'\n", rv, buffer);
+
+  if (!strncmp (SOCK_TEST_MIXED_EPOLL_DATA, (const char *) buffer, nbytes))
+    {
+      rv = write (af_unix_client_fd, buffer, nbytes);
+      if (rv < 0)
+	{
+	  errno_val = errno;
+	  perror ("ERROR in af_unix_echo(): write() failed");
+	  fprintf (stderr,
+		   "SERVER: ERROR: write(af_unix_client_fd %d (0x%x), "
+		   "\"%s\", nbytes %ld) failed (errno = %d)!\n",
+		   af_unix_client_fd, af_unix_client_fd, buffer, nbytes,
+		   errno_val);
+	  goto done;
+	}
+      printf ("SERVER (AF_UNIX): TX (%d bytes) - '%s'\n", rv, buffer);
+      ssm->af_unix_xacts++;
+    }
+done:
+  close (af_unix_client_fd);
+}
+
+#endif
+
 static inline void
 new_client (void)
 {
@@ -398,6 +477,50 @@
     }
 #else
   ssm->listen_fd = socket (AF_INET, SOCK_STREAM, 0);
+#if SOCK_SERVER_USE_EPOLL && !defined (VCL_TEST)
+  unlink ((const char *) SOCK_TEST_AF_UNIX_FILENAME);
+  ssm->af_unix_listen_fd = socket (AF_UNIX, SOCK_STREAM, 0);
+  if (ssm->af_unix_listen_fd < 0)
+    {
+      errno_val = errno;
+      perror ("ERROR in main(): socket(AF_UNIX) failed");
+      fprintf (stderr,
+	       "SERVER: ERROR: socket(AF_UNIX, SOCK_STREAM, 0) failed "
+	       "(errno = %d)!\n", errno_val);
+      return ssm->af_unix_listen_fd;
+    }
+
+  memset (&ssm->serveraddr, 0, sizeof (ssm->serveraddr));
+  ssm->serveraddr.sun_family = AF_UNIX;
+  strcpy (ssm->serveraddr.sun_path, SOCK_TEST_AF_UNIX_FILENAME);
+
+  rv = bind (ssm->af_unix_listen_fd, (struct sockaddr *) &ssm->serveraddr,
+	     SUN_LEN (&ssm->serveraddr));
+  if (rv < 0)
+    {
+      errno_val = errno;
+      perror ("ERROR in main(): bind(SOCK_TEST_AF_UNIX_FILENAME) failed");
+      fprintf (stderr, "SERVER: ERROR: bind() fd %d, \"%s\": "
+	       "failed (errno = %d)!\n", ssm->af_unix_listen_fd,
+	       SOCK_TEST_AF_UNIX_FILENAME, errno_val);
+      close (ssm->af_unix_listen_fd);
+      unlink ((const char *) SOCK_TEST_AF_UNIX_FILENAME);
+      return rv;
+    }
+
+  rv = listen (ssm->af_unix_listen_fd, 10);
+  if (rv < 0)
+    {
+      errno_val = errno;
+      perror ("ERROR in main(): listen(AF_UNIX) failed");
+      fprintf (stderr, "SERVER: ERROR: listen() fd %d, \"%s\": "
+	       "failed (errno = %d)!\n", ssm->af_unix_listen_fd,
+	       SOCK_TEST_AF_UNIX_FILENAME, errno_val);
+      close (ssm->af_unix_listen_fd);
+      unlink ((const char *) SOCK_TEST_AF_UNIX_FILENAME);
+      return rv;
+    }
+#endif /* SOCK_SERVER_USE_EPOLL */
 #endif
   if (ssm->listen_fd < 0)
     {
@@ -457,8 +580,6 @@
       return rv;
     }
 
-  printf ("\nSERVER: Waiting for a client to connect on port %d...\n", port);
-
 #if ! SOCK_SERVER_USE_EPOLL
 
   FD_ZERO (&ssm->wr_fdset);
@@ -492,6 +613,23 @@
   if (rv < 0)
     errno = -rv;
 #else
+  ssm->af_unix_listen_ev.events = EPOLLIN;
+  ssm->af_unix_listen_ev.data.u32 = SOCK_TEST_AF_UNIX_ACCEPT_DATA;
+  rv = epoll_ctl (ssm->epfd, EPOLL_CTL_ADD, ssm->af_unix_listen_fd,
+		  &ssm->af_unix_listen_ev);
+  if (rv < 0)
+    {
+      errno_val = errno;
+      perror ("ERROR in main(): mixed epoll_ctl(EPOLL_CTL_ADD)");
+      fprintf (stderr, "SERVER: ERROR: mixed epoll_ctl(epfd %d (0x%x), "
+	       "EPOLL_CTL_ADD, af_unix_listen_fd %d (0x%x), EPOLLIN) failed "
+	       "(errno = %d)!\n", ssm->epfd, ssm->epfd,
+	       ssm->af_unix_listen_fd, ssm->af_unix_listen_fd, errno_val);
+      close (ssm->af_unix_listen_fd);
+      unlink ((const char *) SOCK_TEST_AF_UNIX_FILENAME);
+      return rv;
+    }
+
   rv = epoll_ctl (ssm->epfd, EPOLL_CTL_ADD, ssm->listen_fd, &ssm->listen_ev);
 #endif
   if (rv < 0)
@@ -504,6 +642,8 @@
     }
 #endif
 
+  printf ("\nSERVER: Waiting for a client to connect on port %d...\n", port);
+
   while (1)
     {
 #if ! SOCK_SERVER_USE_EPOLL
@@ -569,6 +709,14 @@
 	      new_client ();
 	      continue;
 	    }
+#if !defined (VCL_TEST)
+	  else if (ssm->wait_events[i].data.u32 ==
+		   SOCK_TEST_AF_UNIX_ACCEPT_DATA)
+	    {
+	      af_unix_echo ();
+	      continue;
+	    }
+#endif
 	  conn = &ssm->conn_pool[ssm->wait_events[i].data.u32];
 #endif
 	  client_fd = conn->fd;
@@ -732,6 +880,12 @@
   vppcom_app_destroy ();
 #else
   close (ssm->listen_fd);
+
+#if SOCK_SERVER_USE_EPOLL && !defined (VCL_TEST)
+  close (ssm->af_unix_listen_fd);
+  unlink ((const char *) SOCK_TEST_AF_UNIX_FILENAME);
+#endif /* SOCK_SERVER_USE_EPOLL */
+
 #endif
   if (ssm->conn_pool)
     free (ssm->conn_pool);
diff --git a/test/scripts/socket_test.sh b/test/scripts/socket_test.sh
index 96a445e..5b65074 100755
--- a/test/scripts/socket_test.sh
+++ b/test/scripts/socket_test.sh
@@ -526,8 +526,8 @@
     if [ -n "$VCL_DEBUG" ] ; then
         echo "export VCL_DEBUG=$VCL_DEBUG" >> $1
     fi
-    if [ -n "$VCOM_DEBUG" ] ; then
-        echo "export VCOM_DEBUG=$VCOM_DEBUG" >> $1
+    if [ -n "$LDP_DEBUG" ] ; then
+        echo "export LDP_DEBUG=$LDP_DEBUG" >> $1
     fi
     if [ -n "$VCOM_APP_NAME" ] ; then
         echo "export VCOM_APP_NAME=$VCOM_APP_NAME" >> $1