#server auf raspi bauen:

wget https://github.com/open62541/open62541/archive/refs/tags/v1.3.tar.gz
tar -xzf v1.3.tar.gz open62541-1.3/
cd open62541-1.3/

sudo apt install git build-essential gcc pkg-config cmake python3

mkdir build
cd build

cmake -DUA_ENABLE_AMALGAMATION=ON ..
make

ls open62541.*

mkdir -p ~/development/opc-ua/server
cp open62541.*  ~/development/opc-ua/server/

cd ~/development/opc-ua/server/

#folgenden quelltext unter "meinServer.c" speichern:

<----------------------------------------------------------------->
#include "open62541.h"
#include <signal.h>
#include <stdlib.h>

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;
}
<----------------------------------------------------------------->

#serverquelltext compilieren:
gcc -std=c99 open62541.c meinServer.c -o server

#server-binary starten: 
./server


#client auf pc bauen:
sudo apt install python3-pip python3-venv

#virtuelle umgebung aktivieren:
python3 -m venv client
cd client
source ./bin/activate
pip install asyncua

uals --url=opc.tcp://<ip-von-raspi>:4840

pip3 install opcua-client pyqtgraph cryptography numpy

#client starten
opcua-client

#server um variable erweitern

#include "open62541.h"
#include <signal.h>
#include <stdlib.h>

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;
}

static void
addVariable(UA_Server *server) {
    /* Define the attribute of the myInteger variable node */
    UA_VariableAttributes attr = UA_VariableAttributes_default;
    UA_Int32 myInteger = 42;
    UA_Variant_setScalar(&attr.value, &myInteger, &UA_TYPES[UA_TYPES_INT32]);
    attr.description = UA_LOCALIZEDTEXT("en-US","the answer");
    attr.displayName = UA_LOCALIZEDTEXT("en-US","the answer");
    attr.dataType = UA_TYPES[UA_TYPES_INT32].typeId;
    attr.accessLevel = UA_ACCESSLEVELMASK_READ | UA_ACCESSLEVELMASK_WRITE;

    /* Add the variable node to the information model */
    UA_NodeId myIntegerNodeId = UA_NODEID_STRING(1, "the.answer");
    UA_QualifiedName myIntegerName = UA_QUALIFIEDNAME(1, "the answer");
    UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);
    UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES);
    UA_Server_addVariableNode(server, myIntegerNodeId, parentNodeId,
                              parentReferenceNodeId, myIntegerName,
                              UA_NODEID_NUMERIC(0, UA_NS0ID_BASEDATAVARIABLETYPE), attr, NULL, NULL);
}

int main(void) {
    signal(SIGINT, stopHandler);
    signal(SIGTERM, stopHandler);

    UA_Server *server = UA_Server_new();
    UA_ServerConfig_setDefault(UA_Server_getConfig(server));

    addVariable(server);
    
    UA_StatusCode retval = UA_Server_run(server, &running);

    UA_Server_delete(server);
    return retval == UA_STATUSCODE_GOOD ? EXIT_SUCCESS : EXIT_FAILURE;
}