Feature/what is network number handling (#304)

* Add What-Is-Network-Number handling.

Add What-Is-Network-Number and Network-Number-Is network layer handling.
Refactor npdu_encode_npdu_network() from router specific code.
Add unit test for NDPU network message
Add app for What-Is-Network-Number
Add app for Network-Number-Is
Add send helper for What-Is-Network-Number
Add send helper for Network-Number-Is

* added sys/debug.c to ports builds for use of debug_printf() in npdu handler.

Co-authored-by: Steve Karg <skarg@users.sourceforge.net>

CMakeLists.txt

@@ -668,6 +668,12 @@ if(BACNET_STACK_BUILD_APPS)
   add_executable(whoisrouter apps/whoisrouter/main.c)
   target_link_libraries(whoisrouter PRIVATE ${PROJECT_NAME})
 
+  add_executable(whatisnetnum apps/whatisnetnum/main.c)
+  target_link_libraries(whatisnetnum PRIVATE ${PROJECT_NAME})
+
+  add_executable(netnumis apps/netnumis/main.c)
+  target_link_libraries(netnumis PRIVATE ${PROJECT_NAME})
+
   add_executable(writefile apps/writefile/main.c)
   target_link_libraries(writefile PRIVATE ${PROJECT_NAME})
 

Makefile

@@ -109,6 +109,14 @@ readfdt:
 writebdt:
 	$(MAKE) -s -C apps $@
 
+.PHONY: whatisnetnum
+whatisnetnum:
+	$(MAKE) -s -C apps $@
+
+.PHONY: netnumis
+netnumis:
+	$(MAKE) -s -C apps $@
+
 .PHONY: server
 server:
 	$(MAKE) -s -C apps $@

apps/Makefile

@@ -139,7 +139,7 @@ SUBDIRS = lib readprop writeprop readfile writefile reinit server dcc \
 	server-client
 
 ifeq (${BACDL_DEFINE},-DBACDL_BIP=1)
-	SUBDIRS += whoisrouter iamrouter initrouter
+	SUBDIRS += whoisrouter iamrouter initrouter whatisnetnum netnumis
 	ifneq (${BBMD},none)
 	SUBDIRS += readbdt readfdt writebdt
 	endif
@@ -213,6 +213,14 @@ iamrouter: $(BACNET_LIB_TARGET)
 initrouter: $(BACNET_LIB_TARGET)
 	$(MAKE) -b -C $@
 
+.PHONY: whatisnetnum
+whatisnetnum: $(BACNET_LIB_TARGET)
+	$(MAKE) -b -C $@
+
+.PHONY: netnumis
+netnumis: $(BACNET_LIB_TARGET)
+	$(MAKE) -b -C $@
+
 .PHONY: mstpcap
 mstpcap:
 	$(MAKE) -b -C $@

apps/netnumis/Makefile

@@ -0,0 +1,40 @@
+#Makefile to build BACnet Application using GCC compiler
+
+# Executable file name
+TARGET = bacnni
+# BACnet objects that are used with this app
+BACNET_OBJECT_DIR = $(BACNET_SRC_DIR)/bacnet/basic/object
+SRC = main.c \
+	$(BACNET_OBJECT_DIR)/client/device-client.c \
+	$(BACNET_OBJECT_DIR)/netport.c
+
+# TARGET_EXT is defined in apps/Makefile as .exe or nothing
+TARGET_BIN = ${TARGET}$(TARGET_EXT)
+
+OBJS += ${SRC:.c=.o}
+
+all: ${BACNET_LIB_TARGET} Makefile ${TARGET_BIN}
+
+${TARGET_BIN}: ${OBJS} Makefile ${BACNET_LIB_TARGET}
+	${CC} ${PFLAGS} ${OBJS} ${LFLAGS} -o $@
+	size $@
+	cp $@ ../../bin
+
+${BACNET_LIB_TARGET}:
+	( cd ${BACNET_LIB_DIR} ; $(MAKE) clean ; $(MAKE) -s )
+
+.c.o:
+	${CC} -c ${CFLAGS} $*.c -o $@
+
+.PHONY: depend
+depend:
+	rm -f .depend
+	${CC} -MM ${CFLAGS} *.c >> .depend
+
+.PHONY: clean
+clean:
+	rm -f core ${TARGET_BIN} ${OBJS} $(TARGET).map ${BACNET_LIB_TARGET}
+
+.PHONY: include
+include: .depend
+

apps/netnumis/main.c

@@ -0,0 +1,340 @@
+/**
+ * @file
+ * @brief Application to send a BACnet Network Network-Number-Is message
+ * @author Steve Karg <skarg@users.sourceforge.net>
+ * @date July 2022
+ *
+ * SPDX-License-Identifier: MIT
+ */
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h> /* for time */
+#include <errno.h>
+#include "bacnet/bactext.h"
+#include "bacnet/iam.h"
+#include "bacnet/config.h"
+#include "bacnet/bacdef.h"
+#include "bacnet/npdu.h"
+#include "bacnet/apdu.h"
+/* some demo stuff needed */
+#include "bacnet/basic/sys/debug.h"
+#include "bacnet/basic/binding/address.h"
+#include "bacnet/basic/object/device.h"
+#include "bacnet/basic/services.h"
+#include "bacnet/basic/sys/filename.h"
+#include "bacnet/basic/tsm/tsm.h"
+#include "bacnet/datalink/datalink.h"
+#include "bacnet/datalink/dlenv.h"
+
+/* buffer used for receive */
+static uint8_t Rx_Buf[MAX_MPDU] = { 0 };
+
+/* where the message gets sent */
+static BACNET_ADDRESS Target_Router_Address;
+static int32_t Target_Network_Number = 0;
+static int32_t Target_Network_Number_Status = 0;
+
+static bool Error_Detected = false;
+
+/**
+ * Handler for an Abort PDU.
+ * @param src [in] BACNET_ADDRESS of the source of the message
+ * @param invoke_id [in] the invokeID from the rejected message
+ * @param abort_reason [in] the reason for the message abort
+ * @param server
+ */
+static void MyAbortHandler(
+    BACNET_ADDRESS *src, uint8_t invoke_id, uint8_t abort_reason, bool server)
+{
+    /* FIXME: verify src and invoke id */
+    (void)src;
+    (void)invoke_id;
+    (void)server;
+    printf("BACnet Abort: %s\r\n", bactext_abort_reason_name(abort_reason));
+    Error_Detected = true;
+}
+
+/**
+ * @brief Handler for a Reject PDU.
+ * @param src [in] BACNET_ADDRESS of the source of the message
+ * @param invoke_id [in] the invokeID from the rejected message
+ * @param reject_reason [in] the reason for the rejection
+ */
+static void MyRejectHandler(
+    BACNET_ADDRESS *src, uint8_t invoke_id, uint8_t reject_reason)
+{
+    /* FIXME: verify src and invoke id */
+    (void)src;
+    (void)invoke_id;
+    printf("BACnet Reject: %s\r\n", bactext_reject_reason_name(reject_reason));
+    Error_Detected = true;
+}
+
+/**
+ * @brief Handler for a Network messages
+ * @param npdu_data - NPDU options
+ * @param npdu - NPDU data
+ * @param npdu_len - NPDU data length
+ */
+static void My_Router_Handler(BACNET_ADDRESS *src,
+    BACNET_NPDU_DATA *npdu_data,
+    uint8_t *npdu,
+    uint16_t npdu_len)
+{
+    uint16_t dnet = 0;
+    uint16_t len = 0;
+    uint16_t j = 0;
+
+    switch (npdu_data->network_message_type) {
+        case NETWORK_MESSAGE_WHAT_IS_NETWORK_NUMBER:
+            printf("What-Is-Network-Number from ");
+            for (j = 0; j < MAX_MAC_LEN; j++) {
+                if (j < src->mac_len) {
+                    printf("%02X", src->mac[j]);
+                }
+            }
+            printf("\n");
+            break;
+        case NETWORK_MESSAGE_NETWORK_NUMBER_IS:
+            printf("Network-Number-Is from ");
+            for (j = 0; j < MAX_MAC_LEN; j++) {
+                if (j < src->mac_len) {
+                    printf("%02X", src->mac[j]);
+                }
+            }
+            if (src->net == 0) {
+                /*  It shall be transmitted with a local broadcast address,
+                    and shall never be routed. */
+                if (npdu_len >= 2) {
+                    len += decode_unsigned16(npdu, &dnet);
+                    printf(": network number = %u\n", (unsigned)dnet);
+                } else {
+                    printf(": network number = missing!\n");
+                }
+            } else {
+                /*  Devices shall ignore Network-Number-Is messages that
+                    contain SNET/SADR or DNET/DADR information In the NPCI or
+                    that are sent with a local unicast address. */
+                if (npdu_len >= 2) {
+                    len += decode_unsigned16(npdu, &dnet);
+                    printf(": network number = %u. SNET=%u\n",
+                        (unsigned)dnet, (unsigned)src->net);
+                } else {
+                    printf(": network number = missing! SNET=%u\n", src->net);
+                }
+            }
+            break;
+        case NETWORK_MESSAGE_WHO_IS_ROUTER_TO_NETWORK:
+        case NETWORK_MESSAGE_I_AM_ROUTER_TO_NETWORK:
+        case NETWORK_MESSAGE_I_COULD_BE_ROUTER_TO_NETWORK:
+        case NETWORK_MESSAGE_REJECT_MESSAGE_TO_NETWORK:
+        case NETWORK_MESSAGE_ROUTER_BUSY_TO_NETWORK:
+        case NETWORK_MESSAGE_ROUTER_AVAILABLE_TO_NETWORK:
+        case NETWORK_MESSAGE_INIT_RT_TABLE:
+        case NETWORK_MESSAGE_INIT_RT_TABLE_ACK:
+        case NETWORK_MESSAGE_ESTABLISH_CONNECTION_TO_NETWORK:
+        case NETWORK_MESSAGE_DISCONNECT_CONNECTION_TO_NETWORK:
+        default:
+            break;
+    }
+}
+
+static void My_NPDU_Handler(BACNET_ADDRESS *src, /* source address */
+    uint8_t *pdu, /* PDU data */
+    uint16_t pdu_len)
+{ /* length PDU  */
+    int apdu_offset = 0;
+    BACNET_ADDRESS dest = { 0 };
+    BACNET_NPDU_DATA npdu_data = { 0 };
+
+    apdu_offset = npdu_decode(&pdu[0], &dest, src, &npdu_data);
+    if (npdu_data.network_layer_message) {
+        My_Router_Handler(src, &npdu_data, &pdu[apdu_offset],
+            (uint16_t)(pdu_len - apdu_offset));
+    } else if ((apdu_offset > 0) && (apdu_offset <= pdu_len)) {
+        if ((npdu_data.protocol_version == BACNET_PROTOCOL_VERSION) &&
+            ((dest.net == 0) || (dest.net == BACNET_BROADCAST_NETWORK))) {
+            /* only handle the version that we know how to handle */
+            /* and we are not a router, so ignore messages with
+               routing information cause they are not for us */
+            apdu_handler(
+                src, &pdu[apdu_offset], (uint16_t)(pdu_len - apdu_offset));
+        } else {
+            if (dest.net) {
+                debug_printf("NPDU: DNET=%d.  Discarded!\n", dest.net);
+            } else {
+                debug_printf("NPDU: BACnet Protocol Version=%d.  Discarded!\n",
+                    npdu_data.protocol_version);
+            }
+        }
+    }
+
+    return;
+}
+
+static void Init_Service_Handlers(void)
+{
+    Device_Init(NULL);
+    /* we need to handle who-is
+       to support dynamic device binding to us */
+    apdu_set_unconfirmed_handler(SERVICE_UNCONFIRMED_WHO_IS, handler_who_is);
+    /* set the handler for all the services we don't implement
+       It is required to send the proper reject message... */
+    apdu_set_unrecognized_service_handler_handler(handler_unrecognized_service);
+    /* we must implement read property - it's required! */
+    apdu_set_confirmed_handler(
+        SERVICE_CONFIRMED_READ_PROPERTY, handler_read_property);
+    /* handle the reply (request) coming back */
+    apdu_set_unconfirmed_handler(SERVICE_UNCONFIRMED_I_AM, handler_i_am_add);
+    /* handle any errors coming back */
+    apdu_set_abort_handler(MyAbortHandler);
+    apdu_set_reject_handler(MyRejectHandler);
+}
+
+static void address_parse(BACNET_ADDRESS *dst, int argc, char *argv[])
+{
+    int dnet = 0;
+    unsigned mac[6];
+    int count = 0;
+    int index = 0;
+
+    if (argc > 0) {
+        count = sscanf(argv[0], "%x:%x:%x:%x:%x:%x", &mac[0], &mac[1], &mac[2],
+            &mac[3], &mac[4], &mac[5]);
+        dst->mac_len = count;
+        for (index = 0; index < MAX_MAC_LEN; index++) {
+            if (index < count) {
+                dst->mac[index] = mac[index];
+            } else {
+                dst->mac[index] = 0;
+            }
+        }
+    }
+    if (argc > 1) {
+        count = sscanf(argv[1], "%d", &dnet);
+        dst->net = dnet;
+    }
+    if (dnet) {
+        if (argc > 2) {
+            count = sscanf(argv[2], "%x:%x:%x:%x:%x:%x", &mac[0], &mac[1],
+                &mac[2], &mac[3], &mac[4], &mac[5]);
+            dst->len = count;
+            for (index = 0; index < MAX_MAC_LEN; index++) {
+                if (index < count) {
+                    dst->adr[index] = mac[index];
+                } else {
+                    dst->adr[index] = 0;
+                }
+            }
+        } else {
+            fprintf(stderr, "A non-zero DNET requires a DADR.\r\n");
+        }
+    } else {
+        dst->len = 0;
+        for (index = 0; index < MAX_MAC_LEN; index++) {
+            dst->adr[index] = 0;
+        }
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    BACNET_ADDRESS src = { 0 }; /* address where message came from */
+    uint16_t pdu_len = 0;
+    unsigned timeout = 100; /* milliseconds */
+    time_t total_seconds = 0;
+    time_t elapsed_seconds = 0;
+    time_t last_seconds = 0;
+    time_t current_seconds = 0;
+    time_t timeout_seconds = 0;
+
+    if (argc < 3) {
+        printf("Usage: %s DNET status [MAC]\r\n", filename_remove_path(argv[0]));
+        return 0;
+    }
+    if ((argc > 1) && (strcmp(argv[1], "--help") == 0)) {
+        printf("Send BACnet What-Is-Network-Number message to a network.\r\n"
+               "\r\n"
+               "DNET:\r\n"
+               "BACnet destination network number 0-65535\r\n"
+               "To omit the BACnet destination network number, use -1.\r\n"
+               "Network Number Status:\r\n"
+               "0=learned\r\n"
+               "1=configured\r\n"
+               "MAC:\r\n"
+               "Optional MAC address of router for unicast message\r\n"
+               "Format: xx[:xx:xx:xx:xx:xx] [dnet xx[:xx:xx:xx:xx:xx]]\r\n"
+               "Use hexidecimal MAC addresses.\r\n"
+               "\r\n"
+               "To send a What-Is-Network-Number request to DNET 86:\r\n"
+               "%s 86\r\n"
+               "To send a What-Is-Network-Number request to all devices:\r\n"
+               "%s -1\r\n",
+            filename_remove_path(argv[0]), filename_remove_path(argv[0]));
+        return 0;
+    }
+    /* decode the command line parameters */
+    if (argc > 1) {
+        Target_Network_Number = strtol(argv[1], NULL, 0);
+        if (Target_Network_Number > UINT16_MAX) {
+            fprintf(stderr, "DNET=%d - it must be 0 to 65535\r\n",
+                Target_Network_Number);
+            return 1;
+        }
+    }
+    if (argc > 2) {
+        Target_Network_Number_Status = strtol(argv[2], NULL, 0);
+        if (Target_Network_Number > UINT8_MAX) {
+            fprintf(stderr, "status=%d - it must be 0 to 255\r\n",
+                Target_Network_Number_Status);
+            return 1;
+        }
+    }
+    if (argc > 3) {
+        address_parse(&Target_Router_Address, argc - 2, &argv[2]);
+    } else {
+        datalink_get_broadcast_address(&Target_Router_Address);
+    }
+    /* setup my info */
+    Device_Set_Object_Instance_Number(BACNET_MAX_INSTANCE);
+    Init_Service_Handlers();
+    address_init();
+    dlenv_init();
+    atexit(datalink_cleanup);
+    /* configure the timeout values */
+    last_seconds = time(NULL);
+    timeout_seconds = apdu_timeout() / 1000;
+    /* send the request */
+    Send_Network_Number_Is(
+        &Target_Router_Address, Target_Network_Number,
+        Target_Network_Number_Status);
+    /* loop forever */
+    for (;;) {
+        /* increment timer - exit if timed out */
+        current_seconds = time(NULL);
+        /* returns 0 bytes on timeout */
+        pdu_len = datalink_receive(&src, &Rx_Buf[0], MAX_MPDU, timeout);
+        /* process */
+        if (pdu_len) {
+            My_NPDU_Handler(&src, &Rx_Buf[0], pdu_len);
+        }
+        if (Error_Detected) {
+            break;
+}
+        /* increment timer - exit if timed out */
+        elapsed_seconds = current_seconds - last_seconds;
+        if (elapsed_seconds) {
+            datalink_maintenance_timer(elapsed_seconds);
+        }
+        total_seconds += elapsed_seconds;
+        if (total_seconds > timeout_seconds) {
+            break;
+        }
+        /* keep track of time for next check */
+        last_seconds = current_seconds;
+    }
+
+    return 0;
+}

apps/whatisnetnum/Makefile

@@ -0,0 +1,40 @@
+#Makefile to build BACnet Application using GCC compiler
+
+# Executable file name
+TARGET = bacwinn
+# BACnet objects that are used with this app
+BACNET_OBJECT_DIR = $(BACNET_SRC_DIR)/bacnet/basic/object
+SRC = main.c \
+	$(BACNET_OBJECT_DIR)/client/device-client.c \
+	$(BACNET_OBJECT_DIR)/netport.c
+
+# TARGET_EXT is defined in apps/Makefile as .exe or nothing
+TARGET_BIN = ${TARGET}$(TARGET_EXT)
+
+OBJS += ${SRC:.c=.o}
+
+all: ${BACNET_LIB_TARGET} Makefile ${TARGET_BIN}
+
+${TARGET_BIN}: ${OBJS} Makefile ${BACNET_LIB_TARGET}
+	${CC} ${PFLAGS} ${OBJS} ${LFLAGS} -o $@
+	size $@
+	cp $@ ../../bin
+
+${BACNET_LIB_TARGET}:
+	( cd ${BACNET_LIB_DIR} ; $(MAKE) clean ; $(MAKE) -s )
+
+.c.o:
+	${CC} -c ${CFLAGS} $*.c -o $@
+
+.PHONY: depend
+depend:
+	rm -f .depend
+	${CC} -MM ${CFLAGS} *.c >> .depend
+
+.PHONY: clean
+clean:
+	rm -f core ${TARGET_BIN} ${OBJS} $(TARGET).map ${BACNET_LIB_TARGET}
+
+.PHONY: include
+include: .depend
+

apps/whatisnetnum/main.c

@@ -0,0 +1,296 @@
+/**
+ * @file
+ * @brief Application to send a BACnet Network What-Is-Network-Number
+ * @author Steve Karg <skarg@users.sourceforge.net>
+ * @date July 2022
+ *
+ * SPDX-License-Identifier: MIT
+ */
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h> /* for time */
+#include <errno.h>
+#include "bacnet/bactext.h"
+#include "bacnet/iam.h"
+#include "bacnet/config.h"
+#include "bacnet/bacdef.h"
+#include "bacnet/npdu.h"
+#include "bacnet/apdu.h"
+/* some demo stuff needed */
+#include "bacnet/basic/sys/debug.h"
+#include "bacnet/basic/binding/address.h"
+#include "bacnet/basic/object/device.h"
+#include "bacnet/basic/services.h"
+#include "bacnet/basic/sys/filename.h"
+#include "bacnet/basic/tsm/tsm.h"
+#include "bacnet/datalink/datalink.h"
+#include "bacnet/datalink/dlenv.h"
+
+/* buffer used for receive */
+static uint8_t Rx_Buf[MAX_MPDU] = { 0 };
+
+/* where the message gets sent */
+static BACNET_ADDRESS Target_Router_Address;
+
+static bool Error_Detected = false;
+
+/**
+ * Handler for an Abort PDU.
+ * @param src [in] BACNET_ADDRESS of the source of the message
+ * @param invoke_id [in] the invokeID from the rejected message
+ * @param abort_reason [in] the reason for the message abort
+ * @param server
+ */
+static void MyAbortHandler(
+    BACNET_ADDRESS *src, uint8_t invoke_id, uint8_t abort_reason, bool server)
+{
+    /* FIXME: verify src and invoke id */
+    (void)src;
+    (void)invoke_id;
+    (void)server;
+    printf("BACnet Abort: %s\r\n", bactext_abort_reason_name(abort_reason));
+    Error_Detected = true;
+}
+
+/**
+ * @brief Handler for a Reject PDU.
+ * @param src [in] BACNET_ADDRESS of the source of the message
+ * @param invoke_id [in] the invokeID from the rejected message
+ * @param reject_reason [in] the reason for the rejection
+ */
+static void MyRejectHandler(
+    BACNET_ADDRESS *src, uint8_t invoke_id, uint8_t reject_reason)
+{
+    /* FIXME: verify src and invoke id */
+    (void)src;
+    (void)invoke_id;
+    printf("BACnet Reject: %s\r\n", bactext_reject_reason_name(reject_reason));
+    Error_Detected = true;
+}
+
+static void My_Router_Handler(BACNET_ADDRESS *src,
+    BACNET_NPDU_DATA *npdu_data,
+    uint8_t *npdu,
+    uint16_t npdu_len)
+{
+    uint16_t dnet = 0;
+    uint16_t len = 0;
+    uint16_t j = 0;
+
+    switch (npdu_data->network_message_type) {
+        case NETWORK_MESSAGE_WHAT_IS_NETWORK_NUMBER:
+            break;
+        case NETWORK_MESSAGE_NETWORK_NUMBER_IS:
+            printf("Network-Number-Is from ");
+            for (j = 0; j < MAX_MAC_LEN; j++) {
+                if (j < src->mac_len) {
+                    printf("%02X", src->mac[j]);
+                }
+            }
+            if (src->net == 0) {
+                /*  It shall be transmitted with a local broadcast address,
+                    and shall never be routed. */
+                if (npdu_len >= 2) {
+                    len += decode_unsigned16(npdu, &dnet);
+                    printf(": network number = %u\n", (unsigned)dnet);
+                } else {
+                    printf(": network number = missing!\n");
+                }
+            } else {
+                /*  Devices shall ignore Network-Number-Is messages that
+                    contain SNET/SADR or DNET/DADR information In the NPCI or
+                    that are sent with a local unicast address. */
+                if (npdu_len >= 2) {
+                    len += decode_unsigned16(npdu, &dnet);
+                    printf(": network number = %u. SNET=%u\n",
+                        (unsigned)dnet, (unsigned)src->net);
+                } else {
+                    printf(": network number = missing! SNET=%u\n", src->net);
+                }
+            }
+            break;
+        case NETWORK_MESSAGE_WHO_IS_ROUTER_TO_NETWORK:
+        case NETWORK_MESSAGE_I_AM_ROUTER_TO_NETWORK:
+        case NETWORK_MESSAGE_I_COULD_BE_ROUTER_TO_NETWORK:
+        case NETWORK_MESSAGE_REJECT_MESSAGE_TO_NETWORK:
+        case NETWORK_MESSAGE_ROUTER_BUSY_TO_NETWORK:
+        case NETWORK_MESSAGE_ROUTER_AVAILABLE_TO_NETWORK:
+        case NETWORK_MESSAGE_INIT_RT_TABLE:
+        case NETWORK_MESSAGE_INIT_RT_TABLE_ACK:
+        case NETWORK_MESSAGE_ESTABLISH_CONNECTION_TO_NETWORK:
+        case NETWORK_MESSAGE_DISCONNECT_CONNECTION_TO_NETWORK:
+        default:
+            break;
+    }
+}
+
+static void My_NPDU_Handler(BACNET_ADDRESS *src, /* source address */
+    uint8_t *pdu, /* PDU data */
+    uint16_t pdu_len)
+{ /* length PDU  */
+    int apdu_offset = 0;
+    BACNET_ADDRESS dest = { 0 };
+    BACNET_NPDU_DATA npdu_data = { 0 };
+
+    apdu_offset = npdu_decode(&pdu[0], &dest, src, &npdu_data);
+    if (npdu_data.network_layer_message) {
+        My_Router_Handler(src, &npdu_data, &pdu[apdu_offset],
+            (uint16_t)(pdu_len - apdu_offset));
+    } else if ((apdu_offset > 0) && (apdu_offset <= pdu_len)) {
+        if ((npdu_data.protocol_version == BACNET_PROTOCOL_VERSION) &&
+            ((dest.net == 0) || (dest.net == BACNET_BROADCAST_NETWORK))) {
+            /* only handle the version that we know how to handle */
+            /* and we are not a router, so ignore messages with
+               routing information cause they are not for us */
+            apdu_handler(
+                src, &pdu[apdu_offset], (uint16_t)(pdu_len - apdu_offset));
+        } else {
+            if (dest.net) {
+                debug_printf("NPDU: DNET=%d.  Discarded!\n", dest.net);
+            } else {
+                debug_printf("NPDU: BACnet Protocol Version=%d.  Discarded!\n",
+                    npdu_data.protocol_version);
+            }
+        }
+    }
+
+    return;
+}
+
+static void Init_Service_Handlers(void)
+{
+    Device_Init(NULL);
+    /* we need to handle who-is
+       to support dynamic device binding to us */
+    apdu_set_unconfirmed_handler(SERVICE_UNCONFIRMED_WHO_IS, handler_who_is);
+    /* set the handler for all the services we don't implement
+       It is required to send the proper reject message... */
+    apdu_set_unrecognized_service_handler_handler(handler_unrecognized_service);
+    /* we must implement read property - it's required! */
+    apdu_set_confirmed_handler(
+        SERVICE_CONFIRMED_READ_PROPERTY, handler_read_property);
+    /* handle the reply (request) coming back */
+    apdu_set_unconfirmed_handler(SERVICE_UNCONFIRMED_I_AM, handler_i_am_add);
+    /* handle any errors coming back */
+    apdu_set_abort_handler(MyAbortHandler);
+    apdu_set_reject_handler(MyRejectHandler);
+}
+
+static void address_parse(BACNET_ADDRESS *dst, int argc, char *argv[])
+{
+    int dnet = 0;
+    unsigned mac[6];
+    int count = 0;
+    int index = 0;
+
+    if (argc > 0) {
+        count = sscanf(argv[0], "%x:%x:%x:%x:%x:%x", &mac[0], &mac[1], &mac[2],
+            &mac[3], &mac[4], &mac[5]);
+        dst->mac_len = count;
+        for (index = 0; index < MAX_MAC_LEN; index++) {
+            if (index < count) {
+                dst->mac[index] = mac[index];
+            } else {
+                dst->mac[index] = 0;
+            }
+        }
+    }
+    if (argc > 1) {
+        count = sscanf(argv[1], "%d", &dnet);
+        dst->net = dnet;
+    }
+    if (dnet) {
+        if (argc > 2) {
+            count = sscanf(argv[2], "%x:%x:%x:%x:%x:%x", &mac[0], &mac[1],
+                &mac[2], &mac[3], &mac[4], &mac[5]);
+            dst->len = count;
+            for (index = 0; index < MAX_MAC_LEN; index++) {
+                if (index < count) {
+                    dst->adr[index] = mac[index];
+                } else {
+                    dst->adr[index] = 0;
+                }
+            }
+        } else {
+            fprintf(stderr, "A non-zero DNET requires a DADR.\r\n");
+        }
+    } else {
+        dst->len = 0;
+        for (index = 0; index < MAX_MAC_LEN; index++) {
+            dst->adr[index] = 0;
+        }
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    BACNET_ADDRESS src = { 0 }; /* address where message came from */
+    uint16_t pdu_len = 0;
+    unsigned timeout = 100; /* milliseconds */
+    time_t total_seconds = 0;
+    time_t elapsed_seconds = 0;
+    time_t last_seconds = 0;
+    time_t current_seconds = 0;
+    time_t timeout_seconds = 0;
+
+    if ((argc > 1) && (strcmp(argv[1], "--help") == 0)) {
+        printf("Send BACnet What-Is-Network-Number message to a network.\r\n"
+               "\r\n"
+               "MAC:\r\n"
+               "Optional MAC address of router for unicast message\r\n"
+               "Format: xx[:xx:xx:xx:xx:xx] [dnet xx[:xx:xx:xx:xx:xx]]\r\n"
+               "Use hexidecimal MAC addresses.\r\n"
+               "\r\n"
+               "To send a What-Is-Network-Number request to DNET 86:\r\n"
+               "%s 86\r\n"
+               "To send a What-Is-Network-Number request to all devices:\r\n"
+               "%s -1\r\n",
+            filename_remove_path(argv[0]), filename_remove_path(argv[0]));
+        return 0;
+    }
+    if (argc > 1) {
+        address_parse(&Target_Router_Address, argc - 2, &argv[2]);
+    } else {
+        datalink_get_broadcast_address(&Target_Router_Address);
+    }
+    /* setup my info */
+    Device_Set_Object_Instance_Number(BACNET_MAX_INSTANCE);
+    Init_Service_Handlers();
+    address_init();
+    dlenv_init();
+    atexit(datalink_cleanup);
+    /* configure the timeout values */
+    last_seconds = time(NULL);
+    timeout_seconds = apdu_timeout() / 1000;
+    /* send the request */
+    npdu_send_what_is_network_number(&Target_Router_Address);
+    /* loop forever */
+    for (;;) {
+        /* increment timer - exit if timed out */
+        current_seconds = time(NULL);
+        /* returns 0 bytes on timeout */
+        pdu_len = datalink_receive(&src, &Rx_Buf[0], MAX_MPDU, timeout);
+        /* process */
+        if (pdu_len) {
+            My_NPDU_Handler(&src, &Rx_Buf[0], pdu_len);
+        }
+        if (Error_Detected) {
+            break;
+}
+        /* increment timer - exit if timed out */
+        elapsed_seconds = current_seconds - last_seconds;
+        if (elapsed_seconds) {
+            datalink_maintenance_timer(elapsed_seconds);
+        }
+        total_seconds += elapsed_seconds;
+        if (total_seconds > timeout_seconds) {
+            break;
+        }
+        /* keep track of time for next check */
+        last_seconds = current_seconds;
+    }
+
+    return 0;
+}

ports/at91sam7s/Makefile

@@ -68,6 +68,7 @@ DEMOSRC = ai.c \
 	device.c \
 	netport.c \
 	$(BACNET_BASIC)/tsm/tsm.c \
+	$(BACNET_BASIC)/sys/debug.c \
 	$(BACNET_BASIC)/sys/ringbuf.c \
 	$(BACNET_BASIC)/npdu/h_npdu.c \
 	$(BACNET_BASIC)/service/h_noserv.c \

ports/at91sam7s/bacnet.ewp

@@ -1100,6 +1100,9 @@
         <file>
             <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\ringbuf.c</name>
         </file>
+        <file>
+            <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\debug.c</name>
+        </file>
         <file>
             <name>$PROJ_DIR$\..\..\src\bacnet\basic\service\s_iam.c</name>
         </file>

ports/atmega168/Makefile

@@ -51,6 +51,7 @@ CSRC = main.c \
 BASICSRC = $(BACNET_BASIC)/tsm/tsm.c \
 	$(BACNET_BASIC)/npdu/h_npdu.c \
 	$(BACNET_BASIC)/sys/bigend.c \
+	$(BACNET_BASIC)/sys/debug.c \
 	$(BACNET_BASIC)/service/s_iam.c \
 	$(BACNET_BASIC)/service/h_noserv.c
 

ports/atmega168/bacnet.cproj

@@ -156,6 +156,10 @@
       <SubType>compile</SubType>
       <Link>BACnet Handlers\bigend.c</Link>
     </Compile>
+    <Compile Include="..\..\src\bacnet\basic\sys\debug.c">
+      <SubType>compile</SubType>
+      <Link>BACnet Handlers\debug.c</Link>
+    </Compile>
     <Compile Include="..\..\src\bacnet\basic\npdu\h_npdu.c">
       <SubType>compile</SubType>
       <Link>BACnet Handlers\h_npdu.c</Link>

ports/atmega168/bacnet.ewp

@@ -3191,6 +3191,9 @@
         <file>
             <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\bigend.c</name>
         </file>
+        <file>
+            <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\debug.c</name>
+        </file>
         <file>
             <name>$PROJ_DIR$\..\..\src\bacnet\datalink\crc.c</name>
         </file>

ports/bdk-atxx4-mstp/Makefile

@@ -110,6 +110,7 @@ BASICSRC = $(BACNET_BASIC)/service/h_dcc.c \
 	$(BACNET_BASIC)/service/s_iam.c \
 	$(BACNET_BASIC)/service/s_ihave.c \
 	$(BACNET_BASIC)/sys/bigend.c \
+	$(BACNET_BASIC)/sys/debug.c \
 	$(BACNET_BASIC)/sys/fifo.c \
 	$(BACNET_BASIC)/sys/mstimer.c \
 	$(BACNET_BASIC)/sys/ringbuf.c \

ports/bdk-atxx4-mstp/bacnet.cproj

@@ -427,6 +427,10 @@
       <SubType>compile</SubType>
       <Link>BACnet Core\reject.c</Link>
     </Compile>
+    <Compile Include="..\..\src\bacnet\basic\sys\debug.c">
+      <SubType>compile</SubType>
+      <Link>BACnet Core\debug.c</Link>
+    </Compile>
     <Compile Include="..\..\src\bacnet\basic\sys\mstimer.c">
       <SubType>compile</SubType>
       <Link>BACnet Core\mstimer.c</Link>

ports/bdk-atxx4-mstp/bacnet.ewp

@@ -4309,6 +4309,9 @@
     </group>
     <group>
         <name>BACnet Basic Sys</name>
+        <file>
+            <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\debug.c</name>
+        </file>
         <file>
             <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\fifo.c</name>
         </file>

ports/stm32f10x/Makefile

@@ -46,6 +46,7 @@ BASIC_SRC = \
 	$(BACNET_BASIC)/service/s_iam.c \
 	$(BACNET_BASIC)/service/s_ihave.c \
 	$(BACNET_BASIC)/tsm/tsm.c \
+	$(BACNET_BASIC)/sys/debug.c \
 	$(BACNET_BASIC)/sys/ringbuf.c \
 	$(BACNET_BASIC)/sys/fifo.c \
 	$(BACNET_BASIC)/sys/mstimer.c

ports/stm32f10x/bacnet.ewp

@@ -1183,6 +1183,9 @@
         <file>
             <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\bigend.c</name>
         </file>
+        <file>
+            <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\debug.c</name>
+        </file>
         <file>
             <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\fifo.c</name>
         </file>

ports/stm32f4xx/Makefile

@@ -44,6 +44,7 @@ BASIC_SRC = \
 	$(BACNET_BASIC)/service/s_iam.c \
 	$(BACNET_BASIC)/service/s_ihave.c \
 	$(BACNET_BASIC)/tsm/tsm.c \
+	$(BACNET_BASIC)/sys/debug.c \
 	$(BACNET_BASIC)/sys/ringbuf.c \
 	$(BACNET_BASIC)/sys/fifo.c \
 	$(BACNET_BASIC)/sys/mstimer.c

ports/stm32f4xx/bacnet.ewp

@@ -1186,6 +1186,9 @@
         <file>
             <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\bigend.c</name>
         </file>
+        <file>
+            <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\debug.c</name>
+        </file>
         <file>
             <name>$PROJ_DIR$\..\..\src\bacnet\basic\sys\fifo.c</name>
         </file>

ports/xplained/bacnet.cproj

@@ -840,6 +840,10 @@
       <SubType>compile</SubType>
       <Link>bacnet-stack\ringbuf.c</Link>
     </Compile>
+    <Compile Include="..\..\src\bacnet\basic\sys\debug.c">
+      <SubType>compile</SubType>
+      <Link>bacnet-stack\debug.c</Link>
+    </Compile>
     <Compile Include="..\..\src\bacnet\rp.c">
       <SubType>compile</SubType>
       <Link>bacnet-stack\rp.c</Link>

src/bacnet/basic/npdu/h_npdu.c

@@ -24,6 +24,7 @@
  *********************************************************************/
 #include <stdbool.h>
 #include <stdint.h>
+#include "bacnet/bacaddr.h"
 #include "bacnet/bacdef.h"
 #include "bacnet/bacdcode.h"
 #include "bacnet/bacint.h"
@@ -32,13 +33,176 @@
 #include "bacnet/npdu.h"
 #include "bacnet/apdu.h"
 #include "bacnet/basic/services.h"
+#include "bacnet/basic/sys/debug.h"
+#include "bacnet/basic/tsm/tsm.h"
+#include "bacnet/datalink/datalink.h"
 
 #if PRINT_ENABLED
 #include <stdio.h>
 #endif
 
+static uint16_t Local_Network_Number;
+static uint8_t Local_Network_Number_Status = NETWORK_NUMBER_LEARNED;
+
+/**
+ * @brief get the local network number
+ * @return local network number
+ */
+uint16_t npdu_network_number(void)
+{
+    return Local_Network_Number;
+}
+
+/**
+ * @brief set the local network number
+ * @param net - local network number
+ */
+void npdu_network_number_set(uint16_t net)
+{
+    Local_Network_Number =  net;
+}
+
+/**
+ * @brief send the local network number is message
+ * @param dst - the destination address for the message
+ * @param net - local network number
+ * @param status - 0=learned, 1=assigned
+ * @return number of bytes sent
+ */
+int npdu_send_network_number_is(BACNET_ADDRESS *dst,
+    uint16_t net, uint8_t status)
+{
+    uint16_t len = 0;
+    int pdu_len = 0;
+    int bytes_sent = 0;
+    bool data_expecting_reply = false;
+    BACNET_NPDU_DATA npdu_data;
+    BACNET_ADDRESS my_address;
+
+    /*  Upon receipt of a What-Is-Network-Number message,
+        a device that knows the local network number shall
+        transmit a local broadcast Network-Number-Is message
+        back to the source device. */
+    datalink_get_my_address(&my_address);
+    npdu_encode_npdu_network(&npdu_data,
+        NETWORK_MESSAGE_NETWORK_NUMBER_IS,
+        data_expecting_reply, MESSAGE_PRIORITY_NORMAL);
+    pdu_len = npdu_encode_pdu(&Handler_Transmit_Buffer[0], dst,
+        &my_address, &npdu_data);
+    len = encode_unsigned16(
+        &Handler_Transmit_Buffer[pdu_len], net);
+    pdu_len += len;
+    Handler_Transmit_Buffer[pdu_len] = status;
+    pdu_len++;
+    bytes_sent = datalink_send_pdu(
+        dst, &npdu_data, &Handler_Transmit_Buffer[0], pdu_len);
+
+    return bytes_sent;
+}
+
+/**
+ * @brief send the local network number is message
+ * @param dst - the destination address for the message
+ * @param net - local network number
+ * @return number of bytes sent
+ */
+int npdu_send_what_is_network_number(BACNET_ADDRESS *dst)
+{
+    int pdu_len = 0;
+    bool data_expecting_reply = false;
+    BACNET_NPDU_DATA npdu_data;
+    BACNET_ADDRESS daddr = { 0 };
+    BACNET_ADDRESS saddr = { 0 };
+
+    if (dst) {
+        bacnet_address_copy(&daddr, dst);
+    } else {
+        datalink_get_broadcast_address(&daddr);
+    }
+    datalink_get_my_address(&saddr);
+    npdu_encode_npdu_network(&npdu_data,
+        NETWORK_MESSAGE_WHAT_IS_NETWORK_NUMBER,
+        data_expecting_reply, MESSAGE_PRIORITY_NORMAL);
+    pdu_len = npdu_encode_pdu(
+        &Handler_Transmit_Buffer[0],
+        &daddr, &saddr, &npdu_data);
+
+    /* Now send the message */
+    return datalink_send_pdu(
+        dst, &npdu_data, &Handler_Transmit_Buffer[0], pdu_len);
+
+}
+
 /** @file h_npdu.c  Handles messages at the NPDU level of the BACnet stack. */
 
+/** Handler to manage the Network Layer Control Messages received in a packet.
+ *  This handler is called if the NCPI bit 7 indicates that this packet is a
+ *  network layer message and there is no further DNET to pass it to.
+ *  The NCPI has already been decoded into the npdu_data structure.
+ * @ingroup MISCHNDLR
+ *
+ * @param src  [in] The routing source information, if any.
+ *                   If src->net and src->len are 0, there is no
+ *                   routing source information.
+ * @param npdu_data [in] Contains a filled-out structure with information
+ * 					 decoded from the NCPI and other NPDU
+ * bytes.
+ *  @param npdu [in]  Buffer containing the rest of the NPDU, following the
+ *  				 bytes that have already been decoded.
+ *  @param npdu_len [in] The length of the remaining NPDU message in npdu[].
+ */
+static void network_control_handler(BACNET_ADDRESS *src,
+    BACNET_NPDU_DATA *npdu_data,
+    uint8_t *npdu,
+    uint16_t npdu_len)
+{
+    uint16_t dnet = 0;
+    uint16_t len = 0;
+    uint8_t status = 0;
+
+    switch (npdu_data->network_message_type) {
+        case NETWORK_MESSAGE_WHAT_IS_NETWORK_NUMBER:
+            if (src->net == 0) {
+                if (Local_Network_Number) {
+                    npdu_send_network_number_is(src, Local_Network_Number,
+                        Local_Network_Number_Status);
+                } else {
+                    /*  Upon receipt of a What-Is-Network-Number message,
+                        a device that does not know the local network number
+                        shall discard the message. */
+                }
+            } else {
+                /*  Devices shall ignore What-Is-Network-Number messages
+                    that contain SNET/SADR or DNET/DADR information in
+                    the NPCI. */
+            }
+            break;
+        case NETWORK_MESSAGE_NETWORK_NUMBER_IS:
+            if (src->net == 0) {
+                /*  It shall be transmitted with a local broadcast address,
+                    and shall never be routed. */
+                if (npdu_len >= 2) {
+                    (void)decode_unsigned16(npdu, &dnet);
+                    Local_Network_Number = dnet;
+                }
+                if (npdu_len >= 3) {
+                    status = npdu[2];
+                    /*  Our net number is always learned, unless we
+                        are a router.  Ignore the learned/configured
+                        status */
+                    (void)status;
+                }
+            } else {
+                /*  Devices shall ignore Network-Number-Is messages that
+                    contain SNET/SADR or DNET/DADR information In the NPCI or
+                    that are sent with a local unicast address. */
+            }
+            break;
+        default:
+            break;
+    }
+}
+
 /** Handler for the NPDU portion of a received packet.
  *  Aside from error-checking, if the NPDU doesn't contain routing info,
  *  this handler doesn't do much besides stepping over the NPDU header
@@ -62,10 +226,10 @@
  *  @param pdu [in]  Buffer containing the NPDU and APDU of the received packet.
  *  @param pdu_len [in] The size of the received message in the pdu[] buffer.
  */
-void npdu_handler(BACNET_ADDRESS *src, /* source address */
+void npdu_handler(BACNET_ADDRESS *src,
-    uint8_t *pdu, /* PDU data */
+    uint8_t *pdu,
     uint16_t pdu_len)
-{ /* length PDU  */
+{
     int apdu_offset = 0;
     BACNET_ADDRESS dest = { 0 };
     BACNET_NPDU_DATA npdu_data = { 0 };
@@ -79,10 +243,12 @@ void npdu_handler(BACNET_ADDRESS *src, /* source address */
         apdu_offset =
             bacnet_npdu_decode(&pdu[0], pdu_len, &dest, src, &npdu_data);
         if (npdu_data.network_layer_message) {
-            /*FIXME: network layer message received!  Handle it! */
+            if ((dest.net == 0) || (dest.net == BACNET_BROADCAST_NETWORK)) {
-#if PRINT_ENABLED
+                network_control_handler(src, &npdu_data,
-            fprintf(stderr, "NPDU: Network Layer Message discarded!\n");
+                    &pdu[apdu_offset], (uint16_t)(pdu_len - apdu_offset));
-#endif
+            } else {
+                debug_printf("NPDU: message for router. Discarded!\n");
+            }
         } else if ((apdu_offset > 0) && (apdu_offset < pdu_len)) {
             if ((dest.net == 0) || (dest.net == BACNET_BROADCAST_NETWORK)) {
                 /* only handle the version that we know how to handle */

src/bacnet/basic/npdu/h_npdu.h

@@ -47,6 +47,20 @@ extern "C" {
         BACNET_ADDRESS * src,
         uint8_t * pdu,
         uint16_t pdu_len);
+
+    BACNET_STACK_EXPORT
+    uint16_t npdu_network_number(void);
+    BACNET_STACK_EXPORT
+    void npdu_network_number_set(uint16_t net);
+    BACNET_STACK_EXPORT
+    int npdu_send_network_number_is(
+        BACNET_ADDRESS *dst,
+        uint16_t net,
+        uint8_t status);
+    BACNET_STACK_EXPORT
+    int npdu_send_what_is_network_number(
+        BACNET_ADDRESS *dst);
+
     BACNET_STACK_EXPORT
     void npdu_handler_cleanup(void);
     BACNET_STACK_EXPORT

src/bacnet/basic/npdu/h_routed_npdu.c

@@ -161,6 +161,12 @@ static void network_control_handler(BACNET_ADDRESS *src,
         case NETWORK_MESSAGE_DISCONNECT_CONNECTION_TO_NETWORK:
             /* Do nothing - don't support PTP half-router control */
             break;
+        case NETWORK_MESSAGE_WHAT_IS_NETWORK_NUMBER:
+            /* FIXME: add procedure for this message */
+            break;
+        case NETWORK_MESSAGE_NETWORK_NUMBER_IS:
+            /* FIXME: add procedure for this message */
+            break;
         default:
             /* An unrecognized message is bad; send an error response. */
             Send_Reject_Message_To_Network(

src/bacnet/basic/npdu/s_router.c

@@ -29,6 +29,7 @@
 #include "bacnet/config.h"
 #include "bacnet/bacdef.h"
 #include "bacnet/bacdcode.h"
+#include "bacnet/bacaddr.h"
 #include "bacnet/npdu.h"
 #include "bacnet/apdu.h"
 #include "bacnet/bactext.h"
@@ -43,36 +44,6 @@
 /** @file s_router.c  Methods to send various BACnet Router Network Layer
  * Messages. */
 
-/** Initialize an npdu_data structure with given parameters and good defaults,
- * and add the Network Layer Message fields.
- * The name is a misnomer, as it doesn't do any actual encoding here.
- * @see npdu_encode_npdu_data for a simpler version to use when sending an
- *           APDU instead of a Network Layer Message.
- *
- * @param npdu_data [out] Returns a filled-out structure with information
- * 					 provided by the other arguments and
- * good defaults.
- * @param network_message_type [in] The type of Network Layer Message.
- * @param data_expecting_reply [in] True if message should have a reply.
- * @param priority [in] One of the 4 priorities defined in section 6.2.2,
- *                      like B'11' = Life Safety message
- */
-void npdu_encode_npdu_network(BACNET_NPDU_DATA *npdu_data,
-    BACNET_NETWORK_MESSAGE_TYPE network_message_type,
-    bool data_expecting_reply,
-    BACNET_MESSAGE_PRIORITY priority)
-{
-    if (npdu_data) {
-        npdu_data->data_expecting_reply = data_expecting_reply;
-        npdu_data->protocol_version = BACNET_PROTOCOL_VERSION;
-        npdu_data->network_layer_message = true; /* false if APDU */
-        npdu_data->network_message_type = network_message_type; /* optional */
-        npdu_data->vendor_id = 0; /* optional, if net message type is > 0x80 */
-        npdu_data->priority = priority;
-        npdu_data->hop_count = HOP_COUNT_DEFAULT;
-    }
-}
-
 /** Function to encode and send any supported Network Layer Message.
  * The payload for the message is encoded from information in the iArgs[] array.
  * The contents of iArgs are are, per message type:
@@ -150,6 +121,18 @@ int Send_Network_Layer_Message(BACNET_NETWORK_MESSAGE_TYPE network_message_type,
             }
             break;
 
+        case NETWORK_MESSAGE_NETWORK_NUMBER_IS:
+            /* Encode the DNET */
+            len = encode_unsigned16(
+                &Handler_Transmit_Buffer[pdu_len], (uint16_t)*pVal);
+            pdu_len += len;
+            pVal++;
+            /* Encode the Status byte */
+            Handler_Transmit_Buffer[pdu_len] = (uint8_t)*pVal;
+            pdu_len++;
+            pVal++;
+            break;
+
         case NETWORK_MESSAGE_REJECT_MESSAGE_TO_NETWORK:
             /* Encode the Reason byte, then the DNET */
             Handler_Transmit_Buffer[pdu_len++] = (uint8_t)*pVal;
@@ -317,3 +300,23 @@ void Send_Initialize_Routing_Table_Ack(
     Send_Network_Layer_Message(
         NETWORK_MESSAGE_INIT_RT_TABLE_ACK, dst, (int *)DNET_list);
 }
+
+/**
+ * @brief Sets a BACnet network number for the local network
+ *
+ * @param dst [in] If NULL, request will be broadcast to the local BACnet
+ *                 network.  Optionally may designate a particular router
+ *                 destination to respond.
+ * @param dnet [in] Which BACnet network to request for; if -1, no DNET
+ *                 will be sent and the receiving router(s) will send
+ *                 their full list of reachable BACnet networks.
+ */
+void Send_Network_Number_Is(BACNET_ADDRESS *dst, int dnet, int status)
+{
+    int iArgs[2];
+    iArgs[0] = dnet;
+    iArgs[1] = status;
+
+    Send_Network_Layer_Message(
+        NETWORK_MESSAGE_NETWORK_NUMBER_IS, dst, iArgs);
+}

src/bacnet/basic/npdu/s_router.h

@@ -43,12 +43,6 @@ extern "C" {
 #endif /* __cplusplus */
 
     BACNET_STACK_EXPORT
-    void npdu_encode_npdu_network(
-        BACNET_NPDU_DATA *npdu_data,
-        BACNET_NETWORK_MESSAGE_TYPE network_message_type,
-        bool data_expecting_reply,
-        BACNET_MESSAGE_PRIORITY priority);
-    BACNET_STACK_EXPORT
     int Send_Network_Layer_Message(
         BACNET_NETWORK_MESSAGE_TYPE network_message_type,
         BACNET_ADDRESS * dst,
@@ -73,7 +67,11 @@ extern "C" {
     void Send_Initialize_Routing_Table_Ack(
         BACNET_ADDRESS * dst,
         const int DNET_list[]);
-
+    BACNET_STACK_EXPORT
+    void Send_Network_Number_Is(
+        BACNET_ADDRESS *dst,
+        int dnet,
+        int status);
 
 #ifdef __cplusplus
 }

src/bacnet/npdu.c

@@ -286,6 +286,36 @@ void npdu_encode_npdu_data(BACNET_NPDU_DATA *npdu_data,
     }
 }
 
+/** Initialize an npdu_data structure with given parameters and good defaults,
+ * and add the Network Layer Message fields.
+ * The name is a misnomer, as it doesn't do any actual encoding here.
+ * @see npdu_encode_npdu_data for a simpler version to use when sending an
+ *           APDU instead of a Network Layer Message.
+ *
+ * @param npdu_data [out] Returns a filled-out structure with information
+ * 					 provided by the other arguments and
+ * good defaults.
+ * @param network_message_type [in] The type of Network Layer Message.
+ * @param data_expecting_reply [in] True if message should have a reply.
+ * @param priority [in] One of the 4 priorities defined in section 6.2.2,
+ *                      like B'11' = Life Safety message
+ */
+void npdu_encode_npdu_network(BACNET_NPDU_DATA *npdu_data,
+    BACNET_NETWORK_MESSAGE_TYPE network_message_type,
+    bool data_expecting_reply,
+    BACNET_MESSAGE_PRIORITY priority)
+{
+    if (npdu_data) {
+        npdu_data->data_expecting_reply = data_expecting_reply;
+        npdu_data->protocol_version = BACNET_PROTOCOL_VERSION;
+        npdu_data->network_layer_message = true; /* false if APDU */
+        npdu_data->network_message_type = network_message_type; /* optional */
+        npdu_data->vendor_id = 0; /* optional, if net message type is > 0x80 */
+        npdu_data->priority = priority;
+        npdu_data->hop_count = HOP_COUNT_DEFAULT;
+    }
+}
+
 /** Decode the NPDU portion of a received message, particularly the NCPI byte.
  *  The Network Layer Protocol Control Information byte is described
  *  in section 6.2.2 of the BACnet standard.

src/bacnet/npdu.h

@@ -61,6 +61,9 @@ typedef struct router_port_t {
     struct router_port_t *next;         /**< Point to next in linked list */
 } BACNET_ROUTER_PORT;
 
+#define NETWORK_NUMBER_LEARNED 0
+#define NETWORK_NUMBER_CONFIGURED 1
+
 #ifdef __cplusplus
 extern "C" {
 #endif /* __cplusplus */
@@ -83,6 +86,13 @@ extern "C" {
         bool data_expecting_reply,
         BACNET_MESSAGE_PRIORITY priority);
 
+    BACNET_STACK_EXPORT
+    void npdu_encode_npdu_network(
+        BACNET_NPDU_DATA *npdu_data,
+        BACNET_NETWORK_MESSAGE_TYPE network_message_type,
+        bool data_expecting_reply,
+        BACNET_MESSAGE_PRIORITY priority);
+
     BACNET_STACK_EXPORT
     void npdu_copy_data(
         BACNET_NPDU_DATA * dest,

test/bacnet/npdu/src/main.c

@@ -16,6 +16,42 @@
  * @{
  */
 
+/**
+ * @brief Test
+ */
+static void test_NPDU_Network(void)
+{
+    uint8_t pdu[480] = { 0 };
+    BACNET_ADDRESS dest = { 0 };
+    BACNET_ADDRESS src = { 0 };
+    BACNET_ADDRESS npdu_dest = { 0 };
+    BACNET_ADDRESS npdu_src = { 0 };
+    int len = 0;
+    bool data_expecting_reply = true;
+    BACNET_NETWORK_MESSAGE_TYPE network_message_type =
+        NETWORK_MESSAGE_NETWORK_NUMBER_IS;
+    BACNET_MESSAGE_PRIORITY priority = MESSAGE_PRIORITY_NORMAL;
+    BACNET_NPDU_DATA npdu_data = { 0 };
+    int i = 0; /* counter */
+    int npdu_len = 0;
+    bool network_layer_message = true;
+    uint16_t vendor_id = 0; /* optional, if net message type is > 0x80 */
+
+    npdu_encode_npdu_network(&npdu_data,
+        network_message_type,
+        data_expecting_reply, priority);
+    len = npdu_encode_pdu(&pdu[0], &dest, &src, &npdu_data);
+    zassert_not_equal(len, 0, NULL);
+    /* can we get the info back? */
+    npdu_len = npdu_decode(&pdu[0], &npdu_dest, &npdu_src, &npdu_data);
+    zassert_not_equal(npdu_len, 0, NULL);
+    zassert_equal(npdu_data.data_expecting_reply, data_expecting_reply, NULL);
+    zassert_equal(npdu_data.network_layer_message, network_layer_message, NULL);
+    zassert_equal(npdu_data.network_message_type, network_message_type, NULL);
+    zassert_equal(npdu_data.vendor_id, vendor_id, NULL);
+    zassert_equal(npdu_data.priority, priority, NULL);
+}
+
 /**
  * @brief Test
  */
@@ -146,7 +182,8 @@ void test_main(void)
 {
     ztest_test_suite(npdu_tests,
      ztest_unit_test(testNPDU1),
-     ztest_unit_test(testNPDU2)
+     ztest_unit_test(testNPDU2),
+     ztest_unit_test(test_NPDU_Network)
      );
 
     ztest_run_test_suite(npdu_tests);