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116 lines
4.7 KiB
C
116 lines
4.7 KiB
C
/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
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* See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */
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/**
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* Building a Simple Server
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* ------------------------
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*
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* This series of tutorial guide you through your first steps with open62541.
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* For compiling the examples, you need a compiler (MS Visual Studio 2015 or
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* newer, GCC, Clang and MinGW32 are all known to be working). The compilation
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* instructions are given for GCC but should be straightforward to adapt.
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*
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* It will also be very helpful to install an OPC UA Client with a graphical
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* frontend, such as UAExpert by Unified Automation. That will enable you to
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* examine the information model of any OPC UA server.
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*
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* To get started, downdload the open62541 single-file release from
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* http://open62541.org or generate it according to the :ref:`build instructions
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* <building>` with the "amalgamation" option enabled. From now on, we assume
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* you have the ``open62541.c/.h`` files in the current folder. Now create a new
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* C source-file called ``myServer.c`` with the following content: */
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#include <open62541/plugin/log_stdout.h>
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#include <open62541/server.h>
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#include <open62541/server_config_default.h>
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#include <signal.h>
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#include <stdlib.h>
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static volatile UA_Boolean running = true;
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static void stopHandler(int sig) {
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UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "received ctrl-c");
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running = false;
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}
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int main(void) {
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signal(SIGINT, stopHandler);
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signal(SIGTERM, stopHandler);
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UA_Server *server = UA_Server_new();
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UA_ServerConfig_setDefault(UA_Server_getConfig(server));
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UA_StatusCode retval = UA_Server_run(server, &running);
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UA_Server_delete(server);
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return retval == UA_STATUSCODE_GOOD ? EXIT_SUCCESS : EXIT_FAILURE;
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}
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/**
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* This is all that is needed for a simple OPC UA server. With the GCC compiler,
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* the following command produces an executable:
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*
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* .. code-block:: bash
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*
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* $ gcc -std=c99 open62541.c myServer.c -o myServer
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*
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* In a MinGW environment, the Winsock library must be added.
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*
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* .. code-block:: bash
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*
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* $ gcc -std=c99 open62541.c myServer.c -lws2_32 -o myServer.exe
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*
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* Now start the server (stop with ctrl-c):
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*
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* .. code-block:: bash
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*
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* $ ./myServer
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*
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* You have now compiled and run your first OPC UA server. You can go ahead and
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* browse the information model with client. The server is listening on
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* ``opc.tcp://localhost:4840``. In the next two sections, we will continue to
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* explain the different parts of the code in detail.
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*
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* Server Configuration and Plugins
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* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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*
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* *open62541* provides a flexible framework for building OPC UA servers and
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* clients. The goals is to have a core library that accommodates for all use
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* cases and runs on all platforms. Users can then adjust the library to fit
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* their use case via configuration and by developing (platform-specific)
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* plugins. The core library is based on C99 only and does not even require
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* basic POSIX support. For example, the lowlevel networking code is implemented
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* as an exchangeable plugin. But don't worry. *open62541* provides plugin
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* implementations for most platforms and sensible default configurations
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* out-of-the-box.
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*
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* In the above server code, we simply take the default server configuration and
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* add a single TCP network layer that is listerning on port 4840.
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*
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* Server Lifecycle
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* ^^^^^^^^^^^^^^^^
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*
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* The code in this example shows the three parts for server lifecycle
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* management: Creating a server, running the server, and deleting the server.
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* Creating and deleting a server is trivial once the configuration is set up.
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* The server is started with ``UA_Server_run``. Internally, the server then
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* uses timeouts to schedule regular tasks. Between the timeouts, the server
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* listens on the network layer for incoming messages.
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*
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* You might ask how the server knows when to stop running. For this, we have
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* created a global variable ``running``. Furthermore, we have registered the
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* method ``stopHandler`` that catches the signal (interrupt) the program
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* receives when the operating systems tries to close it. This happens for
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* example when you press ctrl-c in a terminal program. The signal handler then
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* sets the variable ``running`` to false and the server shuts down once it
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* takes back control.
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*
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* In order to integrate OPC UA in a single-threaded application with its own
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* mainloop (for example provided by a GUI toolkit), one can alternatively drive
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* the server manually. See the section of the server documentation on
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* :ref:`server-lifecycle` for details.
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*
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* The server configuration and lifecycle management is needed for all servers.
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* We will use it in the following tutorials without further comment.
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*/
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