Added comments

core/net/ipv6/websocket-http-client.c

@@ -62,6 +62,13 @@ send_get(struct websocket_http_client_state *s)
   if(strlen(s->header) > 0) {
     tcp_socket_send_str(tcps, s->header);
   }
+  /* The Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw== header is
+     supposed to be a random value, encoded as base64, that is SHA1
+     hashed by the server and returned in a HTTP header. This is used
+     to make sure that we are not seeing some cached version of this
+     conversation. But we have no SHA1 code by default in Contiki, so
+     we can't check the return value. Therefore we just use a
+     hardcoded value here. */
   tcp_socket_send_str(tcps,
                       "Connection: Upgrade\r\n"
                       "Upgrade: websocket\r\n"
@@ -112,6 +119,8 @@ event(struct tcp_socket *tcps, void *ptr,
   } else if(e == TCP_SOCKET_ABORTED) {
     websocket_http_client_aborted(s);
   } else if(e == TCP_SOCKET_DATA_SENT) {
+    /* We could feed this information up to the websocket.c layer, but
+       we currently do not do that. */
   }
 }
 /*---------------------------------------------------------------------------*/
@@ -131,7 +140,9 @@ parse_header_byte(struct websocket_http_client_state *s,
   /* Skip the space that follow the first part */
   PT_YIELD(&s->parse_header_pt);
 
-  /* Read the first three bytes that consistute the HTTP status code. */
+  /* Read the first three bytes that constistute the HTTP status
+     code. We store the HTTP status code as an integer in the
+     s->http_status field. */
   s->http_status = (b - '0');
   PT_YIELD(&s->parse_header_pt);
   s->http_status = s->http_status * 10 + (b - '0');

core/net/ipv6/websocket.c

@@ -603,7 +603,10 @@ static int
 send_data(struct websocket *s, const void *data,
           uint16_t datalen, uint8_t data_type_opcode)
 {
-  uint8_t buf[WEBSOCKET_MAX_MSGLEN + 4 + 4];
+  uint8_t buf[WEBSOCKET_MAX_MSGLEN + 4 + 4]; /* The extra + 4 + 4 here
+                                                comes from the size of
+                                                the websocket framing
+                                                header. */
   struct websocket_frame_hdr *hdr;
   struct websocket_frame_mask *mask;
 
@@ -616,6 +619,8 @@ send_data(struct websocket *s, const void *data,
     return -1;
   }
 
+  /* We need to have 4 + 4 additional bytes for the websocket framing
+     header. */
   if(4 + 4 + datalen > websocket_http_client_sendbuflen(&s->s)) {
     PRINTF("websocket: too few bytes left (%d left, %d needed)\n",
            websocket_http_client_sendbuflen(&s->s),
@@ -689,6 +694,8 @@ websocket_ping(struct websocket *s)
   struct websocket_frame_hdr *hdr;
   struct websocket_frame_mask *mask;
 
+  /* We need 2 + 4 additional bytes for the websocket framing
+     header. */
   if(2 + 4 > websocket_http_client_sendbuflen(&s->s)) {
     return -1;
   }