diff --git a/bacnet-stack/wp.c b/bacnet-stack/wp.c
new file mode 100644
index 00000000..92840310
--- /dev/null
+++ b/bacnet-stack/wp.c
@@ -0,0 +1,256 @@
+/*####COPYRIGHTBEGIN####
+ -------------------------------------------
+ Copyright (C) 2005 Steve Karg
+
+ This program is free software; you can redistribute it and/or
+ modify it under the terms of the GNU General Public License
+ as published by the Free Software Foundation; either version 2
+ of the License, or (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to:
+ The Free Software Foundation, Inc.
+ 59 Temple Place - Suite 330
+ Boston, MA  02111-1307, USA.
+
+ As a special exception, if other files instantiate templates or
+ use macros or inline functions from this file, or you compile
+ this file and link it with other works to produce a work based
+ on this file, this file does not by itself cause the resulting
+ work to be covered by the GNU General Public License. However
+ the source code for this file must still be made available in
+ accordance with section (3) of the GNU General Public License.
+
+ This exception does not invalidate any other reasons why a work
+ based on this file might be covered by the GNU General Public
+ License.
+ -------------------------------------------
+####COPYRIGHTEND####*/
+#include <stdint.h>
+#include "bacenum.h"
+#include "bacdcode.h"
+#include "bacdef.h"
+#include "device.h"
+#include "rp.h"
+
+// encode service
+int wp_encode_apdu(
+  uint8_t *apdu, 
+  uint8_t invoke_id,
+  BACNET_WRITE_PROPERTY_DATA *data)
+{
+  int len = 0; // length of each encoding
+  int apdu_len = 0; // total length of the apdu, return value
+
+  if (apdu)
+  {
+    apdu[0] = PDU_TYPE_CONFIRMED_SERVICE_REQUEST;
+    apdu[1] = encode_max_segs_max_apdu(0, Device_Max_APDU_Length_Accepted());
+    apdu[2] = invoke_id; 
+    apdu[3] = SERVICE_CONFIRMED_WRITE_PROPERTY;     // service choice
+    apdu_len = 4;
+    apdu_len += encode_context_object_id(&apdu[apdu_len], 0,
+      data->object_type, data->object_instance);
+    apdu_len += encode_context_enumerated(&apdu[apdu_len], 1,
+      data->object_property);
+    /* optional array index; ALL is -1 which is assumed when missing */
+    if (data->array_index != BACNET_ARRAY_ALL)
+      apdu_len += encode_context_unsigned(&apdu[apdu_len], 2,
+        array_index);
+    // propertyValue
+    apdu_len += encode_opening_tag(&apdu[apdu_len], 3);
+    for (len = 0; len < data->property_value_len; len++)
+    {
+      apdu[apdu_len++] = data->property_value[len];
+    }
+    apdu_len += encode_closing_tag(&apdu[apdu_len], 3);
+    // optional priority - 0 if not set, 1..16 if set
+    if (data->priority)
+      apdu_len += = encode_context_unsigned(&apdu[apdu_len], 4,
+        data->priority);
+  }
+  
+  return apdu_len;
+}
+
+// decode the service request only
+int wp_decode_service_request(
+  uint8_t *apdu,
+  unsigned apdu_len,
+  BACNET_WRITE_PROPERTY_DATA *data)
+{
+  int len = 0;
+  int tag_len = 0;
+  uint8_t tag_number = 0;
+  uint32_t len_value_type = 0;
+  int type = 0; // for decoding
+  int property = 0; // for decoding
+  uint32_t unsigned_value = 0;
+
+  // check for value pointers
+  if (apdu_len && data)
+  {
+    // Tag 0: Object ID         
+    if (!decode_is_context_tag(&apdu[len++], 0))
+      return -1;
+    len += decode_object_id(&apdu[len], &type, &data->object_instance);
+    data->object_type = type;
+    // Tag 1: Property ID
+    len += decode_tag_number_and_value(&apdu[len],
+        &tag_number, &len_value_type);
+    if (tag_number != 1)
+      return -1;
+    len += decode_enumerated(&apdu[len], len_value_type, &property);
+    data->object_property = property;
+    // Tag 2: Optional Array Index
+    // note: decode without incrementing len so we can check for opening tag
+    tag_len = decode_tag_number_and_value(&apdu[len],
+      &tag_number, &len_value_type);
+    if (tag_number == 2)
+    {
+      len += tag_len;
+      len += decode_unsigned(&apdu[len], len_value_type,
+        &data->array_index);
+    }
+    else
+      data->array_index = BACNET_ARRAY_ALL;
+    // Tag 3: opening context tag */
+    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
+      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;
+    }
+    else
+      return -1;
+    // Tag 4: optional 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;
+}
+
+int wp_decode_apdu(
+  uint8_t *apdu,
+  unsigned apdu_len,
+  uint8_t *invoke_id,
+  BACNET_WRITE_PROPERTY_DATA *data)
+{
+  int len = 0;
+  int offset = 0;
+
+  if (!apdu)
+    return -1;
+  // optional checking - most likely was already done prior to this call
+  if (apdu[0] != PDU_TYPE_CONFIRMED_SERVICE_REQUEST)
+    return -1;
+  //  apdu[1] = encode_max_segs_max_apdu(0, Device_Max_APDU_Length_Accepted());
+  *invoke_id = apdu[2]; /* invoke id - filled in by net layer */
+  if (apdu[3] != SERVICE_CONFIRMED_WRITE_PROPERTY)
+    return -1;
+  offset = 4;
+
+  if (apdu_len > offset)
+  {
+    len = wp_decode_service_request(
+      &apdu[offset],
+      apdu_len - offset,
+      data);
+  }
+  
+  return len;
+}
+
+#ifdef TEST
+#include <assert.h>
+#include <string.h>
+#include "ctest.h"
+
+void testWriteProperty(Test * pTest)
+{
+  uint8_t apdu[480] = {0};
+  int len = 0;
+  int apdu_len = 0;
+  uint8_t invoke_id = 128;
+  uint8_t test_invoke_id = 0;
+  BACNET_OBJECT_TYPE object_type = OBJECT_CALENDAR;
+  BACNET_OBJECT_TYPE test_object_type = 0;
+  uint32_t object_instance = 1; 
+  uint32_t test_object_instance = 0; 
+  BACNET_PROPERTY_ID object_property = PROP_ARCHIVE;
+  BACNET_PROPERTY_ID test_object_property = 0;
+  int32_t array_index = 2;
+  int32_t test_array_index = 0;
+    
+  len = wp_encode_apdu(
+    &apdu[0],
+    invoke_id,
+    object_type,
+    object_instance,
+    object_property,
+    array_index);
+  ct_test(pTest, len != 0);
+  apdu_len = len;
+
+  len = wp_decode_apdu(
+    &apdu[0],
+    apdu_len,
+    &test_invoke_id,
+    &test_object_type,
+    &test_object_instance,
+    &test_object_property,
+    &test_array_index);
+  ct_test(pTest, len != -1);
+  ct_test(pTest, test_object_type == object_type);
+  ct_test(pTest, test_object_instance == object_instance);
+  ct_test(pTest, test_object_property == object_property);
+  ct_test(pTest, test_array_index == array_index);
+
+  return;
+}
+
+#ifdef TEST_WRITE_PROPERTY
+int main(void)
+{
+    Test *pTest;
+    bool rc;
+
+    pTest = ct_create("BACnet WriteProperty", NULL);
+    /* individual tests */
+    rc = ct_addTestFunction(pTest, testWriteProperty);
+    assert(rc);
+    rc = ct_addTestFunction(pTest, testWritePropertyAck);
+    assert(rc);
+
+    ct_setStream(pTest, stdout);
+    ct_run(pTest);
+    (void) ct_report(pTest);
+    ct_destroy(pTest);
+
+    return 0;
+}
+#endif                          /* TEST_WRITE_PROPERTY */
+#endif                          /* TEST */
diff --git a/bacnet-stack/wp.h b/bacnet-stack/wp.h
new file mode 100644
index 00000000..7430cc5d
--- /dev/null
+++ b/bacnet-stack/wp.h
@@ -0,0 +1,77 @@
+/*####COPYRIGHTBEGIN####
+ -------------------------------------------
+ Copyright (C) 2005 Steve Karg
+
+ This program is free software; you can redistribute it and/or
+ modify it under the terms of the GNU General Public License
+ as published by the Free Software Foundation; either version 2
+ of the License, or (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to:
+ The Free Software Foundation, Inc.
+ 59 Temple Place - Suite 330
+ Boston, MA  02111-1307, USA.
+
+ As a special exception, if other files instantiate templates or
+ use macros or inline functions from this file, or you compile
+ this file and link it with other works to produce a work based
+ on this file, this file does not by itself cause the resulting
+ work to be covered by the GNU General Public License. However
+ the source code for this file must still be made available in
+ accordance with section (3) of the GNU General Public License.
+
+ This exception does not invalidate any other reasons why a work
+ based on this file might be covered by the GNU General Public
+ License.
+ -------------------------------------------
+####COPYRIGHTEND####*/
+#ifndef WRITEPROPERTY_H
+#define WRITEPROPERTY_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+typedef struct BACnet_Write_Property_Data
+{
+  BACNET_OBJECT_TYPE object_type;
+  uint32_t object_instance;
+  BACNET_PROPERTY_ID object_property;
+  int32_t array_index; // use BACNET_ARRAY_ALL when not setting
+  uint8_t *property_value;
+  int property_value_len;
+  uint8_t priority; // use 0 if not setting the priority
+} BACNET_WRITE_PROPERTY_DATA;
+
+// encode service
+int wp_encode_apdu(
+  uint8_t *apdu, 
+  uint8_t invoke_id,
+  BACNET_WRITE_PROPERTY_DATA *data);
+
+// decode the service request only
+int wp_decode_service_request(
+  uint8_t *apdu,
+  unsigned apdu_len,
+  BACNET_WRITE_PROPERTY_DATA *data);
+  
+int wp_decode_apdu(
+  uint8_t *apdu,
+  unsigned apdu_len,
+  uint8_t *invoke_id,
+  BACNET_WRITE_PROPERTY_DATA *data);
+
+#ifdef TEST
+#include "ctest.h"
+
+void test_ReadProperty(Test * pTest);
+void test_ReadPropertyAck(Test * pTest);
+#endif
+
+#endif
+
diff --git a/bacnet-stack/wp.mak b/bacnet-stack/wp.mak
new file mode 100644
index 00000000..4156607f
--- /dev/null
+++ b/bacnet-stack/wp.mak
@@ -0,0 +1,34 @@
+#Makefile to build test case
+CC      = gcc
+BASEDIR = .
+#CFLAGS  = -Wall -I.
+# -g for debugging with gdb
+#CFLAGS  = -Wall -I. -g
+CFLAGS  = -Wall -I. -Itest -DTEST -DTEST_WRITE_PROPERTY -g
+
+SRCS = bacdcode.c \
+       bigend.c \
+       device.c \
+       wp.c \
+       test/ctest.c
+
+OBJS = ${SRCS:.c=.o}
+
+TARGET = writeproperty
+
+all: ${TARGET}
+ 
+${TARGET}: ${OBJS}
+	${CC} -o $@ ${OBJS} 
+
+.c.o:
+	${CC} -c ${CFLAGS} $*.c -o $@
+	
+depend:
+	rm -f .depend
+	${CC} -MM ${CFLAGS} *.c >> .depend
+	
+clean:
+	rm -rf core ${TARGET} $(OBJS) *.bak *.1 *.ini
+
+include: .depend