diff --git a/app/coap/coap_client.h b/app/coap/coap_client.h
index 5559adfe..7f0a457b 100644
--- a/app/coap/coap_client.h
+++ b/app/coap/coap_client.h
@@ -1,11 +1,11 @@
-#ifndef _COAP_SERVER_H
-#define _COAP_SERVER_H 1
+#ifndef _COAP_CLIENT_H
+#define _COAP_CLIENT_H 1
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-size_t coap_server_respond(char *data, unsigned short len, unsigned short size);
+void coap_client_response_handler(char *data, unsigned short len, unsigned short size, const uint32_t ip, const uint32_t port);
 
 #ifdef __cplusplus
 }
diff --git a/app/coap/coap_server.c b/app/coap/coap_server.c
index d87bd8f7..c83df093 100644
--- a/app/coap/coap_server.c
+++ b/app/coap/coap_server.c
@@ -3,14 +3,10 @@
 
 #include "coap.h"
 
-size_t coap_server_respond(char *data, unsigned short len, unsigned short size)
+size_t coap_server_respond(char *req, unsigned short reqlen, char *rsp, unsigned short rsplen)
 {
   NODE_DBG("coap_server_respond is called.\n");
-  if(len>size){
-    NODE_DBG("len:%d, size:%d\n",len,size);
-    return 0;
-  }
-  size_t rsplen = size;
+  size_t rlen = rsplen;
   coap_packet_t pkt;
   uint8_t scratch_raw[4];
   coap_rw_buffer_t scratch_buf = {scratch_raw, sizeof(scratch_raw)};
@@ -18,11 +14,11 @@ size_t coap_server_respond(char *data, unsigned short len, unsigned short size)
 
 #ifdef COAP_DEBUG
   NODE_DBG("Received: ");
-  coap_dump(data, len, true);
+  coap_dump(req, reqlen, true);
   NODE_DBG("\n");
 #endif
 
-  if (0 != (rc = coap_parse(&pkt, data, len))){
+  if (0 != (rc = coap_parse(&pkt, req, reqlen))){
     NODE_DBG("Bad packet rc=%d\n", rc);
     return 0;
   }
@@ -33,7 +29,7 @@ size_t coap_server_respond(char *data, unsigned short len, unsigned short size)
     coap_dumpPacket(&pkt);
 #endif
     coap_handle_req(&scratch_buf, &pkt, &rsppkt);
-    if (0 != (rc = coap_build(data, &rsplen, &rsppkt))){
+    if (0 != (rc = coap_build(rsp, &rlen, &rsppkt))){
       NODE_DBG("coap_build failed rc=%d\n", rc);
       return 0;
     }
@@ -41,13 +37,13 @@ size_t coap_server_respond(char *data, unsigned short len, unsigned short size)
     {
 #ifdef COAP_DEBUG
       NODE_DBG("Responding: ");
-      coap_dump(data, rsplen, true);
+      coap_dump(rsp, rlen, true);
       NODE_DBG("\n");
 #endif
 #ifdef COAP_DEBUG
       coap_dumpPacket(&rsppkt);
 #endif
     }
-    return rsplen;
+    return rlen;
   }
 }
diff --git a/app/coap/coap_server.h b/app/coap/coap_server.h
index 5559adfe..7eb023ec 100644
--- a/app/coap/coap_server.h
+++ b/app/coap/coap_server.h
@@ -5,7 +5,7 @@
 extern "C" {
 #endif
 
-size_t coap_server_respond(char *data, unsigned short len, unsigned short size);
+size_t coap_server_respond(char *req, unsigned short reqlen, char *rsp, unsigned short rsplen);
 
 #ifdef __cplusplus
 }
diff --git a/app/coap/endpoints.c b/app/coap/endpoints.c
index a3d2d9d6..43a44eb1 100644
--- a/app/coap/endpoints.c
+++ b/app/coap/endpoints.c
@@ -8,8 +8,8 @@
 
 #include "os_type.h"
 
-static char rsp[MAX_PAYLOAD_SIZE] = "";
-const uint16_t rsplen = MAX_PAYLOAD_SIZE;
+static char rsp[512] = "";
+const uint16_t rsplen = 512;
 void build_well_known_rsp(void);
 
 void endpoint_setup(void)
@@ -29,6 +29,7 @@ static int handle_get_variable(const coap_endpoint_t *ep, coap_rw_buffer_t *scra
 {
     const coap_option_t *opt;
     uint8_t count;
+    int n;
     if (NULL != (opt = coap_findOptions(inpkt, COAP_OPTION_URI_PATH, &count)))
     {
         if ((count != ep->path->count ) && (count != ep->path->count + 1)) // +1 for /f/[function], /v/[variable]
@@ -54,14 +55,15 @@ static int handle_get_variable(const coap_endpoint_t *ep, coap_rw_buffer_t *scra
                         return coap_make_response(scratch, outpkt, NULL, 0, id_hi, id_lo, &inpkt->tok, COAP_RSPCODE_NOT_FOUND, COAP_CONTENTTYPE_NONE);
                     if(c_strlen(h->name))
                     {
+                        n = lua_gettop(h->L);
                         lua_getglobal(h->L, h->name);
                         if (!lua_isnumber(h->L, -1)) {
                             NODE_DBG ("should be a number.\n");
-                            lua_pop(h->L, 1);
+                            lua_settop(h->L, n);
                             return coap_make_response(scratch, outpkt, NULL, 0, id_hi, id_lo, &inpkt->tok, COAP_RSPCODE_NOT_FOUND, COAP_CONTENTTYPE_NONE);
                         } else {
                             const char *res = lua_tostring(h->L,-1);
-                            lua_pop(h->L, 1);
+                            lua_settop(h->L, n);
                             return coap_make_response(scratch, outpkt, (const uint8_t *)res, c_strlen(res), id_hi, id_lo, &inpkt->tok, COAP_RSPCODE_CONTENT, COAP_CONTENTTYPE_TEXT_PLAIN);
                         }
                     }
@@ -84,6 +86,7 @@ static int handle_post_function(const coap_endpoint_t *ep, coap_rw_buffer_t *scr
 {
     const coap_option_t *opt;
     uint8_t count;
+    int n;
     if (NULL != (opt = coap_findOptions(inpkt, COAP_OPTION_URI_PATH, &count)))
     {
         if ((count != ep->path->count ) && (count != ep->path->count + 1)) // +1 for /f/[function], /v/[variable]
@@ -111,10 +114,11 @@ static int handle_post_function(const coap_endpoint_t *ep, coap_rw_buffer_t *scr
 
                     if(c_strlen(h->name))
                     {
+                        n = lua_gettop(h->L);
                         lua_getglobal(h->L, h->name);
                         if (lua_type(h->L, -1) != LUA_TFUNCTION) {
                             NODE_DBG ("should be a function\n");
-                            lua_pop(h->L, 1);
+                            lua_settop(h->L, n);
                             return coap_make_response(scratch, outpkt, NULL, 0, id_hi, id_lo, &inpkt->tok, COAP_RSPCODE_NOT_FOUND, COAP_CONTENTTYPE_NONE);
                         } else {
                             lua_pushlstring(h->L, inpkt->payload.p, inpkt->payload.len);     // make sure payload.p is filled with '\0' after payload.len, or use lua_pushlstring
@@ -125,14 +129,17 @@ static int handle_post_function(const coap_endpoint_t *ep, coap_rw_buffer_t *scr
                                     size_t len = 0;
                                     const char *ret = luaL_checklstring( h->L, -1, &len );
                                     if(len > MAX_PAYLOAD_SIZE){
+                                        lua_settop(h->L, n);
                                         luaL_error( h->L, "return string:<MAX_PAYLOAD_SIZE" );
                                         return coap_make_response(scratch, outpkt, NULL, 0, id_hi, id_lo, &inpkt->tok, COAP_RSPCODE_NOT_FOUND, COAP_CONTENTTYPE_NONE);
                                     }
                                     NODE_DBG((char *)ret);
                                     NODE_DBG("\n");
+                                    lua_settop(h->L, n);
                                     return coap_make_response(scratch, outpkt, ret, len, id_hi, id_lo, &inpkt->tok, COAP_RSPCODE_CONTENT, COAP_CONTENTTYPE_TEXT_PLAIN);
                                 } 
                             } else {
+                                lua_settop(h->L, n);
                                 return coap_make_response(scratch, outpkt, NULL, 0, id_hi, id_lo, &inpkt->tok, COAP_RSPCODE_CONTENT, COAP_CONTENTTYPE_TEXT_PLAIN);
                             }
                         }
diff --git a/app/include/user_modules.h b/app/include/user_modules.h
index a21cee19..f90109f3 100644
--- a/app/include/user_modules.h
+++ b/app/include/user_modules.h
@@ -27,7 +27,7 @@
 #define LUA_USE_MODULES_OW
 #define LUA_USE_MODULES_BIT
 #define LUA_USE_MODULES_MQTT
-// #define LUA_USE_MODULES_COAP			// need about 4k more ram for now
+// #define LUA_USE_MODULES_COAP			// need about 1k more ram for now
 #define LUA_USE_MODULES_U8G
 #define LUA_USE_MODULES_WS2812
 #endif /* LUA_USE_MODULES */
diff --git a/app/modules/coap.c b/app/modules/coap.c
index 2afb9b54..5a4a433d 100644
--- a/app/modules/coap.c
+++ b/app/modules/coap.c
@@ -37,20 +37,20 @@ static void coap_received(void *arg, char *pdata, unsigned short len)
   struct espconn *pesp_conn = arg;
   lcoap_userdata *cud = (lcoap_userdata *)pesp_conn->reverse;
 
-  static uint8_t buf[MAX_MESSAGE_SIZE+1] = {0}; // +1 for string '\0'
+  // static uint8_t buf[MAX_MESSAGE_SIZE+1] = {0}; // +1 for string '\0'
+  uint8_t buf[MAX_MESSAGE_SIZE+1] = {0}; // +1 for string '\0'
   c_memset(buf, 0, sizeof(buf)); // wipe prev data
 
   if (len > MAX_MESSAGE_SIZE) {
     NODE_DBG("Request Entity Too Large.\n"); // NOTE: should response 4.13 to client...
     return;
-  } else {
-    c_memcpy(buf, pdata, len);
   }
+  // c_memcpy(buf, pdata, len);
 
-  size_t rsplen = coap_server_respond(buf, len, MAX_MESSAGE_SIZE+1);
+  size_t rsplen = coap_server_respond(pdata, len, buf, MAX_MESSAGE_SIZE+1);
   espconn_sent(pesp_conn, (unsigned char *)buf, rsplen);
 
-  c_memset(buf, 0, sizeof(buf));
+  // c_memset(buf, 0, sizeof(buf));
 }
 
 static void coap_sent(void *arg)
@@ -227,26 +227,17 @@ static void coap_response_handler(void *arg, char *pdata, unsigned short len)
   struct espconn *pesp_conn = arg;
 
   coap_packet_t pkt;
-  static uint8_t buf[MAX_MESSAGE_SIZE+1] = {0}; // +1 for string '\0'
+  // static uint8_t buf[MAX_MESSAGE_SIZE+1] = {0}; // +1 for string '\0'
+  uint8_t buf[MAX_MESSAGE_SIZE+1] = {0}; // +1 for string '\0'
   c_memset(buf, 0, sizeof(buf)); // wipe prev data
-  static int n = 0;
 
   int rc;
-  if ((len == 1460) && (1460 <= MAX_MESSAGE_SIZE)){
-    c_memcpy(buf, pdata, len); // max length is 1460, another part of data is coming in next callback
-    n = len;
+  if( len > MAX_MESSAGE_SIZE )
+  {
+    NODE_DBG("Request Entity Too Large.\n"); // NOTE: should response 4.13 to client...
     return;
-  } else {
-    if( len > MAX_MESSAGE_SIZE )
-    {
-      NODE_DBG("Request Entity Too Large.\n"); // NOTE: should response 4.13 to client...
-      c_memset(buf, 0, sizeof(buf)); // wipe prev data
-      n = 0;
-      return;
-    }
-    c_memcpy(buf + n, pdata, len);
-    len += n; // more than 1460
   }
+  c_memcpy(buf, pdata, len);
 
   if (0 != (rc = coap_parse(&pkt, buf, len))){
     NODE_DBG("Bad packet rc=%d\n", rc);
@@ -306,8 +297,7 @@ end:
     if(pesp_conn->proto.udp->remote_port || pesp_conn->proto.udp->local_port)
       espconn_delete(pesp_conn);
   }
-  c_memset(buf, 0, sizeof(buf));
-  n = 0;
+  // c_memset(buf, 0, sizeof(buf));
 }
 
 // Lua: client:request( [CON], uri, [payload] )
diff --git a/examples/fragment.lua b/examples/fragment.lua
index c1cc4fb7..a56e423a 100644
--- a/examples/fragment.lua
+++ b/examples/fragment.lua
@@ -355,8 +355,11 @@ cs:listen(5683)
 myvar=1
 cs:var("myvar") -- get coap://192.168.18.103:5683/v1/v/myvar will return the value of myvar: 1
 
-function myfun()
+-- function should tack one string, return one string.
+function myfun(payload)
 	print("myfun called")
+	respond = "hello"
+	return respond
 end
 cs:func("myfun") -- post coap://192.168.18.103:5683/v1/f/myfun will call myfun