diff --git a/bacnet-stack/Makefile b/bacnet-stack/Makefile
index cbef375b..88fa2832 100644
--- a/bacnet-stack/Makefile
+++ b/bacnet-stack/Makefile
@@ -15,6 +15,7 @@ SRCS = ports/linux/main.c \
        whois.c \
        iam.c \
        rp.c \
+       wp.c \
        device.c \
        ai.c \
        abort.c \
diff --git a/bacnet-stack/ai.c b/bacnet-stack/ai.c
index 8c7a973b..64f99da8 100644
--- a/bacnet-stack/ai.c
+++ b/bacnet-stack/ai.c
@@ -33,6 +33,29 @@
 #include "bacenum.h"
 #include "config.h" // the custom stuff
 
+#define MAX_ANALOG_INPUTS 32
+
+bool Analog_Input_Valid_Instance(uint32_t object_instance)
+{
+  if (object_instance < MAX_ANALOG_INPUTS)
+    return true;
+
+  return false;
+}
+
+unsigned Analog_Input_Count(void)
+{
+  return MAX_ANALOG_INPUTS;
+}
+
+// we simply have 0-n object instances.  Yours might be
+// more complex, and then you need to return the instance
+// that correlates to the correct index
+uint32_t Analog_Input_Index_To_Instance(unsigned index)
+{
+  return index;
+}
+
 int Analog_Input_Encode_Property_APDU(
   uint8_t *apdu,
   uint32_t object_instance,
diff --git a/bacnet-stack/ai.h b/bacnet-stack/ai.h
index eec25909..2fd4493c 100644
--- a/bacnet-stack/ai.h
+++ b/bacnet-stack/ai.h
@@ -29,6 +29,10 @@
 #include <stdint.h>
 #include "bacdef.h"
 
+bool Analog_Input_Valid_Instance(uint32_t object_instance);
+unsigned Analog_Input_Count(void);
+uint32_t Analog_Input_Index_To_Instance(unsigned index);
+
 int Analog_Input_Encode_Property_APDU(
   uint8_t *apdu,
   uint32_t object_instance,
diff --git a/bacnet-stack/bacdcode.c b/bacnet-stack/bacdcode.c
index 3341bce3..feed164f 100644
--- a/bacnet-stack/bacdcode.c
+++ b/bacnet-stack/bacdcode.c
@@ -785,8 +785,8 @@ int decode_object_id(
     int len = 0;
 
     len = decode_unsigned32(apdu,&value);
-    *object_type = ((value >> 22) & 0x3FF);
-    *instance = (value & 0x3FFFFF);
+    *object_type = ((value >> BACNET_INSTANCE_BITS) & BACNET_MAX_OBJECT);
+    *instance = (value & BACNET_MAX_INSTANCE);
 
     return len;
 }
@@ -803,7 +803,8 @@ int encode_bacnet_object_id(
     int len = 0;
 
     type = object_type;
-    value = ((type & 0x3FF) << 22) | (instance & 0x3FFFFF);
+    value = ((type & BACNET_MAX_OBJECT) << BACNET_INSTANCE_BITS) | 
+        (instance & BACNET_MAX_INSTANCE);
     len = encode_unsigned32(apdu,value);
 
     return len;
@@ -1239,6 +1240,17 @@ int decode_date(uint8_t * apdu, int *year, int *month, int *day, int *wday)
     return 4;
 }
 
+// returns the number of apdu bytes consumed
+int encode_simple_ack(uint8_t * apdu, uint8_t invoke_id, 
+  uint8_t service_choice)
+{
+    apdu[0] = PDU_TYPE_SIMPLE_ACK;
+    apdu[1] = invoke_id;
+    apdu[2] = service_choice;
+
+    return 3;
+}
+
 /* end of decoding_encoding.c */
 #ifdef TEST
 #include <assert.h>
diff --git a/bacnet-stack/bacdcode.h b/bacnet-stack/bacdcode.h
index d1db1bab..4a6f9e63 100644
--- a/bacnet-stack/bacdcode.h
+++ b/bacnet-stack/bacdcode.h
@@ -176,4 +176,8 @@ uint8_t encode_max_segs_max_apdu(int max_segs, int max_apdu);
 int decode_max_segs(uint8_t octet);
 int decode_max_apdu(uint8_t octet);
 
+// returns the number of apdu bytes consumed
+int encode_simple_ack(uint8_t * apdu, uint8_t invoke_id, 
+  uint8_t service_choice);
+
 #endif
diff --git a/bacnet-stack/bacdef.h b/bacnet-stack/bacdef.h
index f1c72f94..1ca3a68f 100644
--- a/bacnet-stack/bacdef.h
+++ b/bacnet-stack/bacdef.h
@@ -41,9 +41,11 @@
 // largest BACnet Instance Number
 // Also used as a device instance number wildcard address
 #define BACNET_MAX_INSTANCE (0x3FFFFF)
+#define BACNET_INSTANCE_BITS 22
 // large BACnet Object Type
 #define BACNET_MAX_OBJECT (0x3FF)
 // Array index 0=size of array, n=array element n,  MAX=all array elements
+#define BACNET_ARRAY_LENGTH_INDEX 0
 #define BACNET_ARRAY_ALL (~0)
 
 // embedded systems need fixed name sizes
diff --git a/bacnet-stack/config.h b/bacnet-stack/config.h
index 30e6bcfb..2f847270 100644
--- a/bacnet-stack/config.h
+++ b/bacnet-stack/config.h
@@ -20,6 +20,4 @@
 // requests available.
 #define MAX_TSM_TRANSACTIONS 16
 
-#define MAX_ANALOG_INPUTS 32
-
 #endif
diff --git a/bacnet-stack/device.c b/bacnet-stack/device.c
index 2b36e882..dfc379ee 100644
--- a/bacnet-stack/device.c
+++ b/bacnet-stack/device.c
@@ -29,6 +29,8 @@
 #include "bacdcode.h"
 #include "bacenum.h"
 #include "config.h" // the custom stuff
+#include "ai.h" // object list dependency
+#include "wp.h" // write property handling
 
 static uint32_t Object_Instance_Number = 0;
 // FIXME: it is likely that this name is configurable,
@@ -88,6 +90,13 @@ void Device_Set_Object_Instance_Number(uint32_t object_id)
   Object_Instance_Number = object_id;
 }
 
+bool Device_Valid_Object_Instance_Number(uint32_t object_id)
+{
+  // BACnet allows for a wildcard instance number
+  return ((Object_Instance_Number == object_id) || 
+    (object_id == BACNET_MAX_INSTANCE));
+}
+
 BACNET_DEVICE_STATUS Device_System_Status(void)
 {
   return System_Status;
@@ -215,6 +224,52 @@ void Device_Set_Database_Revision(uint8_t revision)
   Database_Revision = revision;
 }
 
+// Since many network clients depend on the object list
+// for discovery, it must be consistent!
+unsigned Device_Object_List_Count(void)
+{
+  unsigned count = 1;
+
+  count += Analog_Input_Count();
+
+  return count;
+}
+
+bool Device_Object_List_Identifier(unsigned array_index,
+  int *object_type, 
+  uint32_t *instance)
+{
+  bool status = false;
+  unsigned object_index = 0;
+  
+  if (array_index == 1)
+  {
+    *object_type = OBJECT_DEVICE; 
+    *instance = Object_Instance_Number;
+    status = true;
+  }
+
+  if (!status)
+  {
+    // array index starts at 1, and 1 for the device object
+    object_index = array_index - 2;
+    if (object_index < Analog_Input_Count())
+    {
+      *object_type = OBJECT_ANALOG_INPUT; 
+      *instance = Analog_Input_Index_To_Instance(object_index);
+      status = true;
+    }
+  }
+
+  // etc.
+  if (!status)
+  {
+    object_index -= Analog_Input_Count();
+  }
+  
+  return status;  
+}
+
 int Device_Encode_Property_APDU(
   uint8_t *apdu,
   BACNET_PROPERTY_ID property,
@@ -224,6 +279,9 @@ int Device_Encode_Property_APDU(
   int len = 0; // apdu len intermediate value
   BACNET_BIT_STRING bit_string;
   int i = 0;
+  int object_type = 0;
+  uint32_t instance = 0;
+  unsigned count = 0;
   
   switch (property)
   {
@@ -313,47 +371,49 @@ int Device_Encode_Property_APDU(
         apdu_len = encode_tagged_bitstring(&apdu[0], &bit_string);
         break;
     case PROP_OBJECT_LIST:
-      // FIXME: hook into real object list, not just device
+      count = Device_Object_List_Count();
       // Array element zero is the number of objects in the list
-      if (array_index == 0)
-        apdu_len = encode_tagged_unsigned(&apdu[0], 1 + MAX_ANALOG_INPUTS);
+      if (array_index == BACNET_ARRAY_LENGTH_INDEX)
+        apdu_len = encode_tagged_unsigned(&apdu[0], count);
       // if no index was specified, then try to encode the entire list
       // into one packet.  Note that more than likely you will have
       // to return an error if the number of encoded objects exceeds
       // your maximum APDU size.
       else if (array_index == BACNET_ARRAY_ALL)
       {
-        len = encode_tagged_object_id(&apdu[0], OBJECT_DEVICE,
-            Object_Instance_Number);
-        apdu_len = len;
-        for (i = 0; i < MAX_ANALOG_INPUTS; i++)
+        for (i = 1; i <= count; i++)
         {
-          // assume next one is the same size as this one
-          // can we all fit into the APDU?
-          if ((apdu_len + len) >= MAX_APDU)
+          if (Device_Object_List_Identifier(i,&object_type,&instance))
           {
+            len = encode_tagged_object_id(&apdu[0], object_type,
+              instance);
+            apdu_len += len;
+            // assume next one is the same size as this one
+            // can we all fit into the APDU?
+            if ((apdu_len + len) >= MAX_APDU)
+            {
+              // ERROR_CLASS_SERVICES
+              // ERROR_CODE_NO_SPACE_FOR_OBJECT
+              apdu_len = 0;
+              break;
+            }
+          }
+          else
+          {
+            // error: internal error?
             apdu_len = 0;
             break;
           }
-          len = encode_tagged_object_id(&apdu[apdu_len], 
-            OBJECT_ANALOG_INPUT, i);
-          apdu_len += len;
         }
       }
       else
       {
-        // the first object in the list is at index=1
-        if (array_index == 1)
-          apdu_len = encode_tagged_object_id(&apdu[0], OBJECT_DEVICE,
-              Object_Instance_Number);
-        else if (array_index < (2 + MAX_ANALOG_INPUTS))
-        {
-          apdu_len = encode_tagged_object_id(&apdu[0], 
-            OBJECT_ANALOG_INPUT, array_index - 2);
-        }
+        if (Device_Object_List_Identifier(array_index,&object_type,&instance))
+          apdu_len = encode_tagged_object_id(&apdu[0], object_type, instance);
         else
         {
-          // FIXME: handle case where index is beyond our bounds
+          //ERROR_CLASS_PROPERTY
+          //ERROR_CODE_INVALID_ARRAY_INDEX
         }
       }
       break;
@@ -378,6 +438,73 @@ int Device_Encode_Property_APDU(
   return apdu_len;
 }
 
+// we can send an I-Am when our device ID changes
+extern bool I_Am_Request;
+
+// returns true if successful
+bool Device_Write_Property(
+  BACNET_WRITE_PROPERTY_DATA *wp_data,
+  BACNET_ERROR_CLASS *error_class,
+  BACNET_ERROR_CODE *error_code)
+{
+  bool status = false; // return value
+  uint8_t *apdu = NULL;
+  int len = 0;
+  int tag_len = 0;
+  uint8_t tag_number = 0;
+  uint32_t len_value_type = 0;
+  int object_type = 0;
+  uint32_t instance = 0;
+  
+  if (!Device_Valid_Object_Instance_Number(wp_data->object_instance))
+  {
+    *error_class = ERROR_CLASS_OBJECT;
+    *error_code = ERROR_CODE_UNKNOWN_OBJECT;
+    return false;
+  }
+
+  // decode the some of the request
+  apdu = wp_data->property_value;
+  tag_len = decode_tag_number_and_value(&apdu[0],
+    &tag_number, &len_value_type);
+  switch (wp_data->object_property)
+  {
+    case PROP_OBJECT_IDENTIFIER:
+      if (tag_len && (tag_number == BACNET_APPLICATION_TAG_OBJECT_ID))
+      { 
+        // FIXME: are we exceeding the property_value_len?
+        len = decode_object_id(&apdu[tag_len],
+          &object_type, 
+          &instance);
+        if (len && 
+          (object_type == OBJECT_DEVICE) && 
+          (instance <= BACNET_MAX_INSTANCE))
+        {
+          Device_Set_Object_Instance_Number(instance);
+          I_Am_Request = true;
+          status = true;
+        }
+        else
+        {
+          *error_class = ERROR_CLASS_PROPERTY;
+          *error_code = ERROR_CODE_VALUE_OUT_OF_RANGE;
+        }
+      }
+      else
+      {
+        *error_class = ERROR_CLASS_PROPERTY;
+        *error_code = ERROR_CODE_INVALID_DATA_TYPE;
+      }
+      break;
+    default:
+      *error_class = ERROR_CLASS_PROPERTY;
+      *error_code = ERROR_CODE_WRITE_ACCESS_DENIED;
+      break;
+  }
+
+  return status;
+}
+
 #ifdef TEST
 #include <assert.h>
 #include <string.h>
diff --git a/bacnet-stack/device.h b/bacnet-stack/device.h
index 778158c8..faa23471 100644
--- a/bacnet-stack/device.h
+++ b/bacnet-stack/device.h
@@ -38,9 +38,15 @@
 #include <stdint.h>
 #include "bacdef.h"
 #include "bacenum.h"
+#include "wp.h"
 
 uint32_t Device_Object_Instance_Number(void);
 void Device_Set_Object_Instance_Number(uint32_t object_id);
+bool Device_Valid_Object_Instance_Number(uint32_t object_id);
+unsigned Device_Object_List_Count(void);
+bool Device_Object_List_Identifier(unsigned array_index,
+  int *object_type, 
+  uint32_t *instance);
 
 BACNET_DEVICE_STATUS Device_System_Status(void);
 void Device_Set_System_Status(BACNET_DEVICE_STATUS status);
@@ -83,5 +89,10 @@ int Device_Encode_Property_APDU(
   BACNET_PROPERTY_ID property,
   int32_t array_index);
 
+bool Device_Write_Property(
+  BACNET_WRITE_PROPERTY_DATA *wp_data,
+  BACNET_ERROR_CLASS *error_class,
+  BACNET_ERROR_CODE *error_code);
+
 #endif
 
diff --git a/bacnet-stack/ports/linux/main.c b/bacnet-stack/ports/linux/main.c
index 25a61e92..39979f13 100644
--- a/bacnet-stack/ports/linux/main.c
+++ b/bacnet-stack/ports/linux/main.c
@@ -1,19 +1,40 @@
-// This example file is not copyrighted so that you can use it as you wish.
-// Written by Steve Karg - 2005 - skarg@users.sourceforge.net
-// Bug fixes, feature requests, and suggestions are welcome
-
-// This is one way to use the embedded BACnet stack under Linux
+/**************************************************************************
+*
+* Copyright (C) 2005 Steve Karg <skarg@users.sourceforge.net>
+*
+* Permission is hereby granted, free of charge, to any person obtaining
+* a copy of this software and associated documentation files (the
+* "Software"), to deal in the Software without restriction, including
+* without limitation the rights to use, copy, modify, merge, publish,
+* distribute, sublicense, and/or sell copies of the Software, and to
+* permit persons to whom the Software is furnished to do so, subject to
+* the following conditions:
+*
+* The above copyright notice and this permission notice shall be included
+* in all copies or substantial portions of the Software.
+*
+* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*
+*********************************************************************/
 
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include "config.h"
 #include "bacdef.h"
+#include "bacdcode.h"
 #include "npdu.h"
 #include "apdu.h"
 #include "device.h"
 #include "ai.h"
 #include "rp.h"
+#include "wp.h"
 #include "iam.h"
 #include "whois.h"
 #include "reject.h"
@@ -259,7 +280,7 @@ void ReadPropertyHandler(
         }
         break;
       case OBJECT_ANALOG_INPUT:
-        if (object_instance < MAX_ANALOG_INPUTS)
+        if (Analog_Input_Valid_Instance(object_instance))
         {
           len = Analog_Input_Encode_Property_APDU(
             &Temp_Buf[0],
@@ -330,6 +351,121 @@ void ReadPropertyHandler(
   return;
 }
 
+void WritePropertyHandler(
+  uint8_t *service_request,
+  uint16_t service_len,
+  BACNET_ADDRESS *src,
+  BACNET_CONFIRMED_SERVICE_DATA *service_data)
+{
+  BACNET_WRITE_PROPERTY_DATA wp_data;
+  int len = 0;
+  int pdu_len = 0;
+  BACNET_ADDRESS my_address;
+  bool send = false;
+  BACNET_ERROR_CLASS error_class;
+  BACNET_ERROR_CODE error_code;
+
+  // decode the service request only
+  len = wp_decode_service_request(
+    service_request,
+    service_len,
+    &wp_data);
+  fprintf(stderr,"Received Write-Property Request!\n");
+  if (len > 0)
+    fprintf(stderr,"type=%u instance=%u property=%u index=%d\n",
+      wp_data.object_type,
+      wp_data.object_instance,
+      wp_data.object_property,
+      wp_data.array_index);
+  else
+    fprintf(stderr,"Unable to decode Write-Property Request!\n");
+  // prepare a reply
+  ethernet_get_my_address(&my_address);
+  // encode the NPDU portion of the packet
+  pdu_len = npdu_encode_apdu(
+    &Tx_Buf[0],
+    src,
+    &my_address,
+    false,  // true for confirmed messages
+    MESSAGE_PRIORITY_NORMAL);
+  // bad decoding - send an abort
+  if (len == -1)
+  {
+    pdu_len += abort_encode_apdu(
+      &Tx_Buf[pdu_len],
+      service_data->invoke_id,
+      ABORT_REASON_OTHER);
+    fprintf(stderr,"Sent Abort!\n");
+    send = true;
+  }
+  else if (service_data->segmented_message)
+  {
+    pdu_len += abort_encode_apdu(
+      &Tx_Buf[pdu_len],
+      service_data->invoke_id,
+      ABORT_REASON_SEGMENTATION_NOT_SUPPORTED);
+    fprintf(stderr,"Sent Abort!\n");
+    send = true;
+  }
+  else
+  {
+    switch (wp_data.object_type)
+    {
+      case OBJECT_DEVICE:
+        if (Device_Write_Property(&wp_data,&error_class,&error_code))
+        {
+          pdu_len = encode_simple_ack(
+            &Tx_Buf[pdu_len],
+            service_data->invoke_id,
+            SERVICE_CONFIRMED_WRITE_PROPERTY);
+          fprintf(stderr,"Sent Write Property Simple Ack!\n");
+          send = true;
+        }
+        else
+        {
+          pdu_len += bacerror_encode_apdu(
+            &Tx_Buf[pdu_len],
+            service_data->invoke_id,
+            SERVICE_CONFIRMED_WRITE_PROPERTY,
+            error_class,
+            error_code);
+          fprintf(stderr,"Sent Write Property Error!\n");
+          send = true;
+        }
+        break;
+      case OBJECT_ANALOG_INPUT:
+        pdu_len += bacerror_encode_apdu(
+          &Tx_Buf[pdu_len],
+          service_data->invoke_id,
+          SERVICE_CONFIRMED_WRITE_PROPERTY,
+          ERROR_CLASS_PROPERTY,
+          ERROR_CODE_WRITE_ACCESS_DENIED);
+        fprintf(stderr,"Sent Write Access Error!\n");
+        send = true;
+        break;
+      default:
+        pdu_len += bacerror_encode_apdu(
+          &Tx_Buf[pdu_len],
+          service_data->invoke_id,
+          SERVICE_CONFIRMED_WRITE_PROPERTY,
+          ERROR_CLASS_OBJECT,
+          ERROR_CODE_UNKNOWN_OBJECT);
+        fprintf(stderr,"Sent Unknown Object Error!\n");
+        send = true;
+        break;
+    }
+  }
+  if (send)
+  {
+    (void)ethernet_send_pdu(
+      src,  // destination address
+      &Tx_Buf[0],
+      pdu_len); // number of bytes of data
+  }
+
+  return;
+}
+
 static void Init_Device_Parameters(void)
 {
   // configure my initial values
@@ -362,6 +498,9 @@ static void Init_Service_Handlers(void)
   apdu_set_confirmed_handler(
     SERVICE_CONFIRMED_READ_PROPERTY,
     ReadPropertyHandler);
+  apdu_set_confirmed_handler(
+    SERVICE_CONFIRMED_WRITE_PROPERTY,
+    WritePropertyHandler);
 }
 
 int main(int argc, char *argv[])
diff --git a/bacnet-stack/wp.c b/bacnet-stack/wp.c
index f6e58a24..c684cff2 100644
--- a/bacnet-stack/wp.c
+++ b/bacnet-stack/wp.c
@@ -124,16 +124,10 @@ int wp_decode_service_request(
     if (decode_is_opening_tag_number(&apdu[len], 3))
     {
       // a tag number of 3 is not extended so only one octet
-       len++;
-      // don't decode the application data here
+      len++;
+      // don't decode the property value here
       data->property_value = &apdu[len];
-      // get the length of the property data
-      len += decode_tag_number_and_value(&apdu[len],
-        &tag_number, &len_value_type);
-      data->property_value_len = len_value_type;
-      // FIXME: is this the length, value or type?
-      // FIXME: If not len, don't increment
-      len += len_value_type;
+      data->property_value_len = apdu_len - len;
     }
     else
       return -1;
@@ -141,17 +135,6 @@ int wp_decode_service_request(
     // FIXME: if the property value is not easily sized here,
     // then just have the application decode the property value
     // and the priority
-    if (len < apdu_len)
-    {
-      len += decode_tag_number_and_value(&apdu[len],&tag_number,
-        &len_value_type);
-      if (tag_number == 4)
-      {
-        len += decode_unsigned(&apdu[len], len_value_type,
-          &unsigned_value);
-        data->priority = (uint8_t)unsigned_value;
-      }
-    }
   }
 
   return len;
@@ -203,7 +186,7 @@ void testWriteProperty(Test * pTest)
   BACNET_WRITE_PROPERTY_DATA data = {0};
   BACNET_WRITE_PROPERTY_DATA test_data = {0};
 
-  // FIXME: set values for data    
+  // FIXME: test values for data    
   len = wp_encode_apdu(
     &apdu[0],
     invoke_id,