WNMP (Web Network Management Protocol) is a product that enables simple and flexible administration and monitoring of embedded systems using ordinary web-browsers. WNMP includes development tools that make it easy to build custom solutions.
A WNMP client is a program that administers or monitors a system or an embedded device. In contrast to SNMP (Simple Network Management Protocol), no special program is needed on the client side. Instead, ordinary web browsers are used. This makes it easy to work from any kind of computer, including a modern cell phone.
The screenshot above illustrates a possible view of the administration of a device from a web browser. All communication to and from the client uses the web protocol HTTP. This communication can be configured to use any port, including the standard one (TCP port 80).
WNMP operates as a plugin to the Barracuda Embedded Web Server. This server is installed on each device to be monitored, along with the WNMP plugin and data needed. It is possible for the Barracuda Web Server to run a number of other applications concurrently with WNMP.
The parameters to be monitored and/or modified via WNMP are defined in separate modules. The WMNP plugin is then initialized with all the modules desired for a particular device. Each module contains a number of parameters to display and/or modify. Each parameter has one of several possible data types, such as 32- or 64-bit integers, strings, enumerations, etc. A parameter can be either read-only or read-write.
A graphical program, the WNMP Editor, is available for easy creation and maintenance of WNMP modules and their parameters. Each WNMP module is defined in a corresponding model file, which details all the parameters, their data types, etc. The WNMP Editor edits these models and also supports importing existing MIB files from SNMP into the model. The WNMP Editor is interactive, which makes it possible to easily modify structures and data types as the model is being developed.
When the model is ready for testing, the C source code for the corresponding WNMP module can be generated. This code generation will create all the source code needed for plugging the module into WNMP. It will also generate convenient stub functions for the get and set operations needed for the module. It is possible to test the module without implementing all of the operations at once.
The WNMP editor is implemented in the Java programming language and requires a Java Virtual machine equal to or above version "1.4". The Barracuda "bin" directory contains a script that simplifies starting the editor. The Windows version of the script is called WnmpEditor.bat and the UNIX version is called WnmpEditor.sh.
All parameters in WNMP are structured into directories. When importing an SNMP MIB, the OID tree is used as the directory tree. The imported directory tree from a MIB can be manipulated and simplified in the WNMP Editor if desired. The directory structure corresponds directly with the URLs visible in the web browser when navigating the WNMP device.
The data types supported in WNMP are the following:
Each of these types are mapped to its own presentation and editing control in HTML.
The WNMP model is fully editable in the WNMP editor. Parameters can be created, renamed, and deleted by right-clicking in the left-side tree view. See the figure below for the popup menu that is shown.
By choosing the move operations in this popup menu, the parameters can be reordered within a directory. It is also possible to move parameters between directories by dragging them in the tree view.
Changing the data type for a parameter is also easy in the WNMP Editor. Just select the parameter from the left-side tree view and modify the access, type, and description in the right-side form. The enumeration and bitset data types also need defined values for the allowed values or bits. These are edited in a name and value table just below the type selector. New values can be created by right-clicking the table and choosing from the popup menu. See the figure below for an example:
As before, the order of the values can also be changed by choosing the move options in the popup menu.
The WNMP module, corresponding to the WNMP model, can be generated from the WNMP Editor. Choose the "Source" menu and open the code generation dialog. The figure below shows the dialog:
The output directory and the WNMP module name must be specified. The module name is the base name for all the generated files and the WNMP module class created inside the same files.
Once the WNMP module source code has been generated, it is possible to build the WNMP plugin for Barracuda. Of course, it will not be possible to edit or display any values for the device unless the corresponding callback-functions have also been implemented. It is possible, though, to navigate the directories and the model structure. See the figure below for a simple example on how to create a Barracuda server with a single Coffee WNMP module.
#include "HttpServer.h"
#include "HttpServCon.h"
#include "wnmp.h"
#include "coffee.h"
int main(char **argv) {
ThreadMutex m;
SoDisp dispatcher;
HttpServer server;
HttpServCon serverCon;
HttpDir rootDir;
WnmpDir wnmpDir;
CoffeeModulecoffeeModule;
int port = 8080;
#ifdef WIN32
// Perform Win32 initialization
WORD wVersionRequested;
WSADATA wsaData;
wVersionRequested = MAKEWORD(1, 1);
if (WSAStartup(wVersionRequested, &wsaData)) {
perror("WSAStartup");
}
#endif
// Create HTTP server
ThreadMutex_constructor(&m);
SoDisp_constructor(&dispatcher,&m);
HttpServer_constructor(&server, &dispatcher, NULL);
HttpServCon_constructor(&serverCon, &server, port, AF_INET, 0, 0);
if (!HttpServCon_isValid(&serverCon)) {
perror("Couldn't create HTTP server connection");
return;
}
// Create WNMP directory structure
HttpDir_constructor(&rootDir, 0, 0);
WnmpDir_constructor(&wnmpDir);
HttpDir_insertDir(&rootDir, (HttpDir*) &wnmpDir);
HttpServer_insertRootDir(&server, &rootDir);
// Create and add WNMP modules
CoffeeModule_constructor(&coffeeModule);
WnmpDir_addModule(&wnmpDir, &coffeeModule);
// TODO: To add more modules here, copy the two lines above and
// change the module name.
// Run HTTP server
for(;;) {
SoDisp_run(&dispatcher, 0);
}
}
The above code is also available as a part of WNMP, in the
test/c subdirectory. The part of the code that
needs to be modified when adding new modules is only the part marked
with a TODO comment.
The WNMP Editor also generates callback functions for all the get and set operations needed to implement the WNMP module. The default implementation for all these functions is to report an error back to WNMP. To implement these functions the real parameter value must be calculated or obtained from the device and the WNMP return code should be set to zero (0). See the example below:
U32 testIntU32 = 0xffffffff;
int getWnmpTestIntU32(U32* value) {
*value = testIntU32;
return 0;
}
int setWnmpTestIntU32(U32 value) {
testIntU32 = value;
return 0;
}
The above code does not retrieve any value from the device, but only from a module local variable. However, it shows how values are retrieved and modified in WNMP. If a value cannot be set or retrieved from the device, a non-zero return code from the callback functions can be used to alert the user.