diff --git a/src/core/ipv4/ip_addr.c b/src/core/ipv4/ip_addr.c
index c83dacb0..83da77f7 100644
--- a/src/core/ipv4/ip_addr.c
+++ b/src/core/ipv4/ip_addr.c
@@ -33,9 +33,6 @@
 #include "lwip/ip_addr.h"
 #include "lwip/inet.h"
 
+/* used by IP_ADDR_ANY and IP_ADDR_BROADCAST in ip_addr.h */
 const struct ip_addr ip_addr_any = { 0x00000000UL };
 const struct ip_addr ip_addr_broadcast = { 0xffffffffUL };
-
-/*-----------------------------------------------------------------------------------*/
-
-/*-----------------------------------------------------------------------------------*/
diff --git a/src/core/pbuf.c b/src/core/pbuf.c
index 993201eb..ead20bee 100644
--- a/src/core/pbuf.c
+++ b/src/core/pbuf.c
@@ -529,10 +529,11 @@ pbuf_free(struct pbuf *p)
    */
   SYS_ARCH_PROTECT(old_level);
   /* de-allocate all consecutive pbufs from the head of the chain that
-   * obtain a zero reference count */
+   * obtain a zero reference count after decrementing*/
   while (p != NULL) {
     /* all pbufs in a chain are referenced at least once */
     LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
+    /* decrease reference count (number of pointers to pbuf) */
     p->ref--;
     /* this pbuf is no longer referenced to? */
     if (p->ref == 0) {
@@ -543,10 +544,10 @@ pbuf_free(struct pbuf *p)
         p->len = p->tot_len = PBUF_POOL_BUFSIZE;
         p->payload = (void *)((u8_t *)p + sizeof(struct pbuf));
         PBUF_POOL_FREE(p);
-      /* a RAM/ROM referencing pbuf */
+      /* a ROM or RAM referencing pbuf */
       } else if (p->flags == PBUF_FLAG_ROM || p->flags == PBUF_FLAG_REF) {
         memp_freep(MEMP_PBUF, p);
-      /* pbuf with data */
+      /* p->flags == PBUF_FLAG_RAM */
       } else {
         mem_free(p);
       }
@@ -554,7 +555,7 @@ pbuf_free(struct pbuf *p)
       /* proceed to next pbuf */
       p = q;
     /* p->ref > 0, this pbuf is still referenced to */
-    /* (so the remaining pbufs in chain as well)    */
+    /* (and so the remaining pbufs in chain as well) */
     } else {
       /* stop walking through chain */
       p = NULL;
diff --git a/src/core/tcp.c b/src/core/tcp.c
index 663a5d9b..b4771364 100644
--- a/src/core/tcp.c
+++ b/src/core/tcp.c
@@ -266,9 +266,9 @@ tcp_bind(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)
       cpcb != NULL; cpcb = cpcb->next) {
     if(cpcb->local_port == port) {
       if(ip_addr_isany(&(cpcb->local_ip)) ||
-	 ip_addr_isany(ipaddr) ||
-	 ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
-	return ERR_USE;
+        ip_addr_isany(ipaddr) ||
+        ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
+          return ERR_USE;
       }
     }
   }
@@ -467,16 +467,16 @@ tcp_slowtmr(void)
   u32_t eff_wnd;
   u8_t pcb_remove;      /* flag if a PCB should be removed */
   err_t err;
-  
+
   err = ERR_OK;
 
   ++tcp_ticks;
-  
+
   /* Steps through all of the active PCBs. */
   prev = NULL;
   pcb = tcp_active_pcbs;
   if (pcb == NULL) DEBUGF(TCP_DEBUG, ("tcp_slowtmr: no active pcbs\n"));
-  while(pcb != NULL) {
+  while (pcb != NULL) {
     DEBUGF(TCP_DEBUG, ("tcp_slowtmr: processing active pcb\n"));
     LWIP_ASSERT("tcp_slowtmr: active pcb->state != CLOSED\n", pcb->state != CLOSED);
     LWIP_ASSERT("tcp_slowtmr: active pcb->state != LISTEN\n", pcb->state != LISTEN);
@@ -484,29 +484,27 @@ tcp_slowtmr(void)
 
     pcb_remove = 0;
 
-    if(pcb->state == SYN_SENT && pcb->nrtx == TCP_SYNMAXRTX) {
+    if (pcb->state == SYN_SENT && pcb->nrtx == TCP_SYNMAXRTX) {
       ++pcb_remove;
       DEBUGF(TCP_DEBUG, ("tcp_slowtmr: max SYN retries reached\n"));
     }
-    else if(pcb->nrtx == TCP_MAXRTX) {
+    else if (pcb->nrtx == TCP_MAXRTX) {
       ++pcb_remove;
       DEBUGF(TCP_DEBUG, ("tcp_slowtmr: max DATA retries reached\n"));
     } else {
       ++pcb->rtime;
-      if(pcb->unacked != NULL && pcb->rtime >= pcb->rto) {
+      if (pcb->unacked != NULL && pcb->rtime >= pcb->rto) {
 
-	/* Time for a retransmission. */
+        /* Time for a retransmission. */
         DEBUGF(TCP_RTO_DEBUG, ("tcp_slowtmr: rtime %u pcb->rto %u\n",
-                               pcb->rtime, pcb->rto));
+          pcb->rtime, pcb->rto));
 
-	/* Double retransmission time-out unless we are trying to
-           connect to somebody (i.e., we are in SYN_SENT). */
-	if(pcb->state != SYN_SENT) {
-	  pcb->rto = ((pcb->sa >> 3) + pcb->sv) << tcp_backoff[pcb->nrtx];
-	}
-
-	tcp_rexmit(pcb);
-	
+        /* Double retransmission time-out unless we are trying to
+         * connect to somebody (i.e., we are in SYN_SENT). */
+        if (pcb->state != SYN_SENT) {
+          pcb->rto = ((pcb->sa >> 3) + pcb->sv) << tcp_backoff[pcb->nrtx];
+        }
+        tcp_rexmit(pcb);
         /* Reduce congestion window and ssthresh. */
         eff_wnd = MIN(pcb->cwnd, pcb->snd_wnd);
         pcb->ssthresh = eff_wnd >> 1;
@@ -514,16 +512,14 @@ tcp_slowtmr(void)
           pcb->ssthresh = pcb->mss * 2;
         }
         pcb->cwnd = pcb->mss;
-
         DEBUGF(TCP_CWND_DEBUG, ("tcp_slowtmr: cwnd %u ssthresh %u\n",
                                 pcb->cwnd, pcb->ssthresh));
       }
     }
-	  
     /* Check if this PCB has stayed too long in FIN-WAIT-2 */
-    if(pcb->state == FIN_WAIT_2) {
+    if (pcb->state == FIN_WAIT_2) {
       if((u32_t)(tcp_ticks - pcb->tmr) >
-	 TCP_FIN_WAIT_TIMEOUT / TCP_SLOW_INTERVAL) {
+        TCP_FIN_WAIT_TIMEOUT / TCP_SLOW_INTERVAL) {
         ++pcb_remove;
         DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in FIN-WAIT-2\n"));
       }
diff --git a/src/core/udp.c b/src/core/udp.c
index d85ba41c..759b4090 100644
--- a/src/core/udp.c
+++ b/src/core/udp.c
@@ -337,12 +337,12 @@ udp_send(struct udp_pcb *pcb, struct pbuf *p)
 
   DEBUGF(UDP_DEBUG | DBG_TRACE | 3, ("udp_send\n"));
 
-  /* if the PCB is not yet bound, bind it here */
+  /* if the PCB is not yet bound to a port, bind it here */
   if (pcb->local_port == 0) {
-    DEBUGF(UDP_DEBUG | DBG_TRACE | 2, ("udp_send: not yet bound\n"));
+    DEBUGF(UDP_DEBUG | DBG_TRACE | 2, ("udp_send: not yet bound to a port, binding now\n"));
     err = udp_bind(pcb, &pcb->local_ip, pcb->local_port);
     if (err != ERR_OK) {
-      DEBUGF(UDP_DEBUG | DBG_TRACE | 2, ("udp_send: forced bind failed\n"));
+      DEBUGF(UDP_DEBUG | DBG_TRACE | 2, ("udp_send: forced port bind failed\n"));
       return err;
     }
   }
@@ -360,6 +360,7 @@ udp_send(struct udp_pcb *pcb, struct pbuf *p)
     pbuf_chain(q, p);
     /* { first pbuf q points to header pbuf } */
     DEBUGF(UDP_DEBUG, ("udp_send: added header pbuf %p before given pbuf %p\n", (void *)q, (void *)p));
+  /* adding a header within p succeeded */
   }	else {
     /* first pbuf q equals given pbuf */
     q = p;
@@ -371,7 +372,7 @@ udp_send(struct udp_pcb *pcb, struct pbuf *p)
   udphdr->dest = htons(pcb->remote_port);
   udphdr->chksum = 0x0000;
 
-  if((netif = ip_route(&(pcb->remote_ip))) == NULL) {
+  if ((netif = ip_route(&(pcb->remote_ip))) == NULL) {
     DEBUGF(UDP_DEBUG | 1, ("udp_send: No route to 0x%lx\n", pcb->remote_ip.addr));
 #ifdef UDP_STATS
     ++lwip_stats.udp.rterr;
@@ -379,8 +380,8 @@ udp_send(struct udp_pcb *pcb, struct pbuf *p)
     return ERR_RTE;
   }
   /* using IP_ANY_ADDR? */
-  if(ip_addr_isany(&pcb->local_ip)) {
-    /* use network interface IP address as source address */
+  if (ip_addr_isany(&pcb->local_ip)) {
+    /* use outgoing network interface IP address as source address */
     src_ip = &(netif->ip_addr);
   } else {
     /* use UDP PCB local IP address as source address */
@@ -390,7 +391,7 @@ udp_send(struct udp_pcb *pcb, struct pbuf *p)
   DEBUGF(UDP_DEBUG, ("udp_send: sending datagram of length %u\n", q->tot_len));
   
   /* UDP Lite protocol? */
-  if(pcb->flags & UDP_FLAGS_UDPLITE) {
+  if (pcb->flags & UDP_FLAGS_UDPLITE) {
     DEBUGF(UDP_DEBUG, ("udp_send: UDP LITE packet length %u\n", q->tot_len));
     /* set UDP message length in UDP header */
     udphdr->len = htons(pcb->chksum_len);
@@ -406,10 +407,10 @@ udp_send(struct udp_pcb *pcb, struct pbuf *p)
     DEBUGF(UDP_DEBUG, ("udp_send: UDP packet length %u\n", q->tot_len));
     udphdr->len = htons(q->tot_len);
     /* calculate checksum */
-    if((pcb->flags & UDP_FLAGS_NOCHKSUM) == 0) {
+    if ((pcb->flags & UDP_FLAGS_NOCHKSUM) == 0) {
       udphdr->chksum = inet_chksum_pseudo(q, src_ip, &pcb->remote_ip, IP_PROTO_UDP, q->tot_len);
       /* chksum zero must become 0xffff, as zero means 'no checksum' */
-      if(udphdr->chksum == 0x0000) udphdr->chksum = 0xffff;
+      if (udphdr->chksum == 0x0000) udphdr->chksum = 0xffff;
     }
     DEBUGF(UDP_DEBUG, ("udp_send: UDP checksum 0x%04x\n", udphdr->chksum));
     snmp_inc_udpoutdatagrams();
@@ -453,7 +454,7 @@ udp_bind(struct udp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)
   DEBUGF(UDP_DEBUG | DBG_TRACE | 3, ("udp_bind(ipaddr = %lx, port = %u)\n", ipaddr->addr, port));
   rebind = 0;
   /* Check for double bind and rebind of the same pcb */
-  for(ipcb = udp_pcbs; ipcb != NULL; ipcb = ipcb->next) {
+  for (ipcb = udp_pcbs; ipcb != NULL; ipcb = ipcb->next) {
     /* is this UDP PCB already on active list? */ 
     if (pcb == ipcb) {
       /* pcb may occur at most once in active list */
diff --git a/src/include/lwip/tcp.h b/src/include/lwip/tcp.h
index b10eb7ea..893b53b4 100644
--- a/src/include/lwip/tcp.h
+++ b/src/include/lwip/tcp.h
@@ -208,7 +208,6 @@ struct tcp_pcb {
   /* receiver varables */
   u32_t rcv_nxt;   /* next seqno expected */
   u16_t rcv_wnd;   /* receiver window */
-
   
   /* Timers */
   u32_t tmr;
diff --git a/src/include/lwip/udp.h b/src/include/lwip/udp.h
index 9d27d0d9..ffadc690 100644
--- a/src/include/lwip/udp.h
+++ b/src/include/lwip/udp.h
@@ -72,10 +72,10 @@ struct udp_pcb {
 struct udp_pcb * udp_new        (void);
 void             udp_remove     (struct udp_pcb *pcb);
 err_t            udp_bind       (struct udp_pcb *pcb, struct ip_addr *ipaddr,
-				 u16_t port);
+                 u16_t port);
 err_t            udp_connect    (struct udp_pcb *pcb, struct ip_addr *ipaddr,
-				 u16_t port);
-void            udp_disconnect    (struct udp_pcb *pcb);
+                 u16_t port);
+void             udp_disconnect    (struct udp_pcb *pcb);
 void             udp_recv       (struct udp_pcb *pcb,
 				 void (* recv)(void *arg, struct udp_pcb *upcb,
 					       struct pbuf *p,