diff --git a/src/api/sockets.c b/src/api/sockets.c
index 8b03e8f4..e3ab4df3 100644
--- a/src/api/sockets.c
+++ b/src/api/sockets.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001-2003 Swedish Institute of Computer Science.
+ * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modification,
@@ -1079,7 +1079,7 @@ int lwip_getsockopt (int s, int level, int optname, void *optval, socklen_t *opt
     /* UNIMPL case SO_DONTROUTE: */
     case SO_KEEPALIVE:
     /* UNIMPL case SO_OOBINCLUDE: */
-#ifdef SO_REUSE
+#if SO_REUSE
     case SO_REUSEADDR:
     case SO_REUSEPORT:
 #endif /* SO_REUSE */
@@ -1182,7 +1182,7 @@ int lwip_setsockopt (int s, int level, int optname, const void *optval, socklen_
     /* UNIMPL case SO_SNDBUF: */
     /* UNIMPL case SO_RCVLOWAT: */
     /* UNIMPL case SO_SNDLOWAT: */
-#ifdef SO_REUSE
+#if SO_REUSE
     case SO_REUSEADDR:
     case SO_REUSEPORT:
 #endif /* SO_REUSE */
@@ -1264,7 +1264,7 @@ int lwip_setsockopt (int s, int level, int optname, const void *optval, socklen_
     /* UNIMPL case SO_DONTROUTE: */
     case SO_KEEPALIVE:
     /* UNIMPL case SO_OOBINCLUDE: */
-#ifdef SO_REUSE
+#if SO_REUSE
     case SO_REUSEADDR:
     case SO_REUSEPORT:
 #endif /* SO_REUSE */
diff --git a/src/core/tcp.c b/src/core/tcp.c
index f7c76572..35ad15f1 100644
--- a/src/core/tcp.c
+++ b/src/core/tcp.c
@@ -5,7 +5,7 @@
  */
 
 /*
- * Copyright (c) 2001-2003 Swedish Institute of Computer Science.
+ * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
  * All rights reserved. 
  * 
  * Redistribution and use in source and binary forms, with or without modification, 
@@ -249,7 +249,7 @@ tcp_bind(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)
   if (port == 0) {
     port = tcp_new_port();
   }
-#ifndef SO_REUSE
+#if SO_REUSE == 0
   /* Check if the address already is in use. */
   for(cpcb = (struct tcp_pcb *)tcp_listen_pcbs;
       cpcb != NULL; cpcb = cpcb->next) {
@@ -444,6 +444,16 @@ tcp_recved(struct tcp_pcb *pcb, u16_t len)
   }
   if (!(pcb->flags & TF_ACK_DELAY) &&
      !(pcb->flags & TF_ACK_NOW)) {
+    /*
+     * We send an ACK here (if one is not already pending, hence
+     * the above tests) as tcp_recved() implies that the application
+     * has processed some data, and so we can open the receiver's
+     * window to allow more to be transmitted.  This could result in
+     * two ACKs being sent for each received packet in some limited cases
+     * (where the application is only receiving data, and is slow to
+     * process it) but it is necessary to guarantee that the sender can
+     * continue to transmit.
+     */
     tcp_ack(pcb);
   }
 
diff --git a/src/core/tcp_in.c b/src/core/tcp_in.c
index f9d5bd8b..d09e1c70 100644
--- a/src/core/tcp_in.c
+++ b/src/core/tcp_in.c
@@ -5,7 +5,7 @@
  */
 
 /*
- * Copyright (c) 2001-2003 Swedish Institute of Computer Science.
+ * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without modification,
@@ -153,7 +153,6 @@ tcp_input(struct pbuf *p, struct netif *inp)
     return;
   }
 
-
   /* Move the payload pointer in the pbuf so that it points to the
      TCP data instead of the TCP header. */
   hdrlen = TCPH_HDRLEN(tcphdr);
@@ -173,7 +172,7 @@ tcp_input(struct pbuf *p, struct netif *inp)
      for an active connection. */
   prev = NULL;
 
-#ifdef SO_REUSE
+#if SO_REUSE
   pcb_temp = tcp_active_pcbs;
   
  again_1:
@@ -191,7 +190,7 @@ tcp_input(struct pbuf *p, struct netif *inp)
        ip_addr_cmp(&(pcb->remote_ip), &(iphdr->src)) &&
        ip_addr_cmp(&(pcb->local_ip), &(iphdr->dest))) {
 
-#ifdef SO_REUSE
+#if SO_REUSE
       if(pcb->so_options & SOF_REUSEPORT) {
         if(reuse) {
           /* We processed one PCB already */
@@ -361,7 +360,7 @@ tcp_input(struct pbuf *p, struct netif *inp)
     tcp_debug_print_state(pcb->state);
 #endif /* TCP_DEBUG */
 #endif /* TCP_INPUT_DEBUG */
-#ifdef SO_REUSE
+#if SO_REUSE
     /* First socket should receive now */
     if(reuse_port) {
       LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: searching next PCB.\n"));
@@ -373,7 +372,7 @@ tcp_input(struct pbuf *p, struct netif *inp)
 #endif /* SO_REUSE */
 
   } else {
-#ifdef SO_REUSE
+#if SO_REUSE
     if(reuse) {
       LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_input: freeing PBUF with reference counter set to %i\n", p->ref));
       pbuf_free(p);
@@ -392,7 +391,7 @@ tcp_input(struct pbuf *p, struct netif *inp)
     }
     pbuf_free(p);
   }
-#ifdef SO_REUSE
+#if SO_REUSE
  end:
 #endif /* SO_REUSE */
   LWIP_ASSERT("tcp_input: tcp_pcbs_sane()", tcp_pcbs_sane());