diff --git a/configs/clicker2-stm32/README.txt b/configs/clicker2-stm32/README.txt
index ae090f760c..af3cdcf38c 100644
--- a/configs/clicker2-stm32/README.txt
+++ b/configs/clicker2-stm32/README.txt
@@ -513,11 +513,8 @@ Configurations
           logic.  A major redesign was done to better handle ACKs and
           retransmissions, and to work with TCP dynamic windowing.
 
-       2017-05-25:  TCP w/HC06 currently sends on packet than hangs.  That
-          one packet is 1220 bytes long (of 4096 byte total message length).
-          It is received by the server application correctly.  The hang is
-          probably due to remaining ACK-related problems. One retransmission
-          is recorded in network stastics.
+       2017-05-25:  After some rather extensive debug, the TCP test was made
+          to with (HC06 and short addressing).
 
      Test Matrix:
        The following configurations have been tested:
@@ -525,7 +522,7 @@ Configurations
                                 TEST DATE
          COMPRESSION ADDRESSING UDP  TCP
          ----------- ---------- ---- ----
-         hc06        short      6/21 ---
+         hc06        short      6/21 6/25
                      extended   6/22 ---
          hc1         short      6/23 ---
                      extended   6/23 ---
@@ -597,10 +594,10 @@ Configurations
        emptied and dumped to the system logging device (USART3 in this
        configuration):
 
-       CONFIG_USBDEV_TRACE=y                   : Enable USB trace feature
-       CONFIG_USBDEV_TRACE_NRECORDS=128        : Buffer 128 records in memory
-       CONFIG_NSH_USBDEV_TRACE=n               : No builtin tracing from NSH
-       CONFIG_NSH_ARCHINIT=y                   : Automatically start the USB monitor
+       CONFIG_USBDEV_TRACE=y            : Enable USB trace feature
+       CONFIG_USBDEV_TRACE_NRECORDS=128 : Buffer 128 records in memory
+       CONFIG_NSH_USBDEV_TRACE=n        : No builtin tracing from NSH
+       CONFIG_NSH_ARCHINIT=y            : Automatically start the USB monitor
        CONFIG_USBMONITOR=y              : Enable the USB monitor daemon
        CONFIG_USBMONITOR_STACKSIZE=2048 : USB monitor daemon stack size
        CONFIG_USBMONITOR_PRIORITY=50    : USB monitor daemon priority
diff --git a/net/sixlowpan/sixlowpan_tcpsend.c b/net/sixlowpan/sixlowpan_tcpsend.c
index d79a1f8a65..4e3701e6fe 100644
--- a/net/sixlowpan/sixlowpan_tcpsend.c
+++ b/net/sixlowpan/sixlowpan_tcpsend.c
@@ -477,8 +477,6 @@ static uint16_t tcp_send_interrupt(FAR struct net_driver_s *dev,
       uint16_t winleft;
       uint16_t sndlen;
 
-      DEBUGASSERT((flags & WPAN_POLL) != 0);
-
       /* Get the amount of TCP payload data that we can send in the next
        * packet.
        */
@@ -537,15 +535,32 @@ static uint16_t tcp_send_interrupt(FAR struct net_driver_s *dev,
               goto end_wait;
             }
 
-          /* Increment the count of bytes sent and count of packets sent */
+          /* Increment the count of bytes sent, the number of unacked bytes,
+           * and the total count of TCP packets sent.
+           *
+           * NOTE: tcp_appsend() normally increments conn->unacked based on
+           * the value of dev->d_sndlen.  However, dev->d_len is always
+           * zero for 6LoWPAN since it does no send via the dev->d_bufuse
+           * but, rather, uses a backdoor frame interface with the IEEE
+           * 802.15.4 MAC.
+           */
+
+          sinfo->s_sent   += sndlen;
+          conn->unacked   += sndlen;
+
+#ifdef CONFIG_NET_TCP_WRITE_BUFFERS
+          /* For compability with buffered send logic */
+
+          conn->sndseq_max = tcp_addsequence(conn->sndseq, conn->unacked);
+#endif
 
-          sinfo->s_sent += sndlen;
 #ifdef CONFIG_NET_STATISTICS
           g_netstats.tcp.sent++;
 #endif
 
-          ninfo("Sent: acked=%d sent=%d buflen=%d\n",
-                sinfo->s_acked, sinfo->s_sent, sinfo->s_buflen);
+          ninfo("Sent: acked=%d sent=%d buflen=%d unacked=%d\n",
+                sinfo->s_acked, sinfo->s_sent, sinfo->s_buflen,
+                conn->unacked);
         }
     }
 
@@ -642,7 +657,7 @@ static int sixlowpan_send_packet(FAR struct socket *psock,
        * device related events, no connect-related events.
        */
 
-      sinfo.s_cb = devif_callback_alloc(dev, &conn->list);
+      sinfo.s_cb = tcp_callback_alloc(conn);
       if (sinfo.s_cb != NULL)
         {
           int ret;
@@ -666,7 +681,8 @@ static int sixlowpan_send_packet(FAR struct socket *psock,
 
           /* Set up the callback in the connection */
 
-          sinfo.s_cb->flags = (NETDEV_DOWN | WPAN_POLL);
+          sinfo.s_cb->flags = (NETDEV_DOWN | TCP_ACKDATA | TCP_REXMIT |
+                               TCP_DISCONN_EVENTS | WPAN_POLL);
           sinfo.s_cb->priv  = (FAR void *)&sinfo;
           sinfo.s_cb->event = tcp_send_interrupt;
 
@@ -696,7 +712,7 @@ static int sixlowpan_send_packet(FAR struct socket *psock,
 
           /* Make sure that no further interrupts are processed */
 
-           devif_conn_callback_free(dev, sinfo.s_cb, &conn->list);
+          tcp_callback_free(conn, sinfo.s_cb);
         }
     }
 
diff --git a/net/tcp/tcp_input.c b/net/tcp/tcp_input.c
index 10be0edc78..8b34988401 100644
--- a/net/tcp/tcp_input.c
+++ b/net/tcp/tcp_input.c
@@ -451,8 +451,10 @@ found:
 
           if ((conn->tcpstateflags & TCP_STATE_MASK) == TCP_ESTABLISHED)
             {
-              nwarn("WARNING: conn->sndseq %d, conn->unacked %d\n",
-                    tcp_getsequence(conn->sndseq), conn->unacked);
+              nwarn("WARNING: ackseq > unackseq\n");
+              nwarn("         sndseq=%u unacked=%u unackseq=%u ackseq=%u\n",
+                    tcp_getsequence(conn->sndseq), conn->unacked, unackseq,
+                    ackseq);
               goto reset;
             }
         }