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