modbus_server.c

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/**
 * @file modbus_server.c
 * @brief Modbus/TCP server
 *
 * @section License
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Copyright (C) 2010-2026 Oryx Embedded SARL. All rights reserved.
 *
 * This file is part of CycloneTCP Open.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * @author Oryx Embedded SARL (www.oryx-embedded.com)
 * @version 2.6.0
 **/
 
//Switch to the appropriate trace level
#define TRACE_LEVEL MODBUS_TRACE_LEVEL
 
//Dependencies
#include "modbus/modbus_server.h"
#include "modbus/modbus_server_transport.h"
#include "modbus/modbus_server_misc.h"
#include "debug.h"
 
//Check TCP/IP stack configuration
#if (MODBUS_SERVER_SUPPORT == ENABLED)
 
 
/**
 * @brief Initialize settings with default values
 * @param[out] settings Structure that contains Modbus/TCP server settings
 **/
 
void modbusServerGetDefaultSettings(ModbusServerSettings *settings)
{
   //Default task parameters
   settings->task = OS_TASK_DEFAULT_PARAMS;
   settings->task.stackSize = MODBUS_SERVER_STACK_SIZE;
   settings->task.priority = MODBUS_SERVER_PRIORITY;
 
   //TCP/IP stack context
   settings->netContext = NULL;
   //The Modbus/TCP server is not bound to any interface
   settings->interface = NULL;
 
   //Modbus/TCP port number
   settings->port = MODBUS_TCP_PORT;
   //Default unit identifier
   settings->unitId = MODBUS_DEFAULT_UNIT_ID;
   //Idle connection timeout
   settings->timeout = MODBUS_SERVER_TIMEOUT;
 
   //TCP connection open callback function
   settings->openCallback = NULL;
   //TCP connection close callback function
   settings->closeCallback = NULL;
 
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED)
   //TLS initialization callback function
   settings->tlsInitCallback = NULL;
#endif
 
   //Lock Modbus table callback function
   settings->lockCallback = NULL;
   //Unlock Modbus table callback function
   settings->unlockCallback = NULL;
   //Get coil state callback function
   settings->readCoilCallback = NULL;
   //Get discrete input state callback function
   settings->readDiscreteInputCallback = NULL;
   //Set coil state callback function
   settings->writeCoilCallback = NULL;
   //Get register value callback function
   settings->readRegCallback = NULL;
   //Get holding register value callback function
   settings->readHoldingRegCallback = NULL;
   //Get input register value callback function
   settings->readInputRegCallback = NULL;
   //Set register value callback function
   settings->writeRegCallback = NULL;
   //PDU processing callback
   settings->processPduCallback = NULL;
   //Tick callback function
   settings->tickCallback = NULL;
}
 
 
/**
 * @brief Initialize Modbus/TCP server context
 * @param[in] context Pointer to the Modbus/TCP server context
 * @param[in] settings Modbus/TCP server specific settings
 * @return Error code
 **/
 
error_t modbusServerInit(ModbusServerContext *context,
   const ModbusServerSettings *settings)
{
   error_t error;
 
   //Debug message
   TRACE_INFO("Initializing Modbus/TCP server...\r\n");
 
   //Ensure the parameters are valid
   if(context == NULL || settings == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Initialize status code
   error = NO_ERROR;
 
   //Clear Modbus/TCP server context
   osMemset(context, 0, sizeof(ModbusServerContext));
 
   //Initialize task parameters
   context->taskParams = settings->task;
   context->taskId = OS_INVALID_TASK_ID;
 
   //Attach TCP/IP stack context
   if(settings->netContext != NULL)
   {
      context->netContext = settings->netContext;
   }
   else if(settings->interface != NULL)
   {
      context->netContext = settings->interface->netContext;
   }
   else
   {
      context->netContext = netGetDefaultContext();
   }
 
   //Save user settings
   context->interface = settings->interface;
   context->port = settings->port;
   context->unitId = settings->unitId;
   context->timeout = settings->timeout;
   context->openCallback = settings->openCallback;
   context->closeCallback = settings->closeCallback;
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED)
   context->tlsInitCallback = settings->tlsInitCallback;
#endif
   context->lockCallback = settings->lockCallback;
   context->unlockCallback = settings->unlockCallback;
   context->readCoilCallback = settings->readCoilCallback;
   context->readDiscreteInputCallback = settings->readDiscreteInputCallback;
   context->writeCoilCallback = settings->writeCoilCallback;
   context->readRegCallback = settings->readRegCallback;
   context->readHoldingRegCallback = settings->readHoldingRegCallback;
   context->readInputRegCallback = settings->readInputRegCallback;
   context->writeRegCallback = settings->writeRegCallback;
   context->processPduCallback = settings->processPduCallback;
   context->tickCallback = settings->tickCallback;
 
   //Create an event object to poll the state of sockets
   if(!osCreateEvent(&context->event))
   {
      //Failed to create event
      error = ERROR_OUT_OF_RESOURCES;
   }
 
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED && TLS_TICKET_SUPPORT == ENABLED)
   //Check status code
   if(!error)
   {
      //Initialize ticket encryption context
      error = tlsInitTicketContext(&context->tlsTicketContext);
   }
#endif
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      modbusServerDeinit(context);
   }
 
   //Return status code
   return error;
}
 
 
/**
 * @brief Start Modbus/TCP server
 * @param[in] context Pointer to the Modbus/TCP server context
 * @return Error code
 **/
 
error_t modbusServerStart(ModbusServerContext *context)
{
   error_t error;
 
   //Make sure the Modbus/TCP server context is valid
   if(context == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Debug message
   TRACE_INFO("Starting Modbus/TCP server...\r\n");
 
   //Make sure the Modbus/TCP server is not already running
   if(context->running)
      return ERROR_ALREADY_RUNNING;
 
   //Start of exception handling block
   do
   {
      //Open a TCP socket
      context->socket = socketOpenEx(context->netContext, SOCKET_TYPE_STREAM,
         SOCKET_IP_PROTO_TCP);
      //Failed to open socket?
      if(context->socket == NULL)
      {
         //Report an error
         error = ERROR_OPEN_FAILED;
         break;
      }
 
      //Force the socket to operate in non-blocking mode
      error = socketSetTimeout(context->socket, 0);
      //Any error to report?
      if(error)
         break;
 
      //Associate the socket with the relevant interface
      error = socketBindToInterface(context->socket, context->interface);
      //Any error to report?
      if(error)
         break;
 
      //The Modbus/TCP server listens for connection requests on port 502
      error = socketBind(context->socket, &IP_ADDR_ANY, context->port);
      //Any error to report?
      if(error)
         break;
 
      //Place socket in listening state
      error = socketListen(context->socket, 0);
      //Any error to report?
      if(error)
         break;
 
      //Start the Modbus/TCP server
      context->stop = FALSE;
      context->running = TRUE;
 
      //Create a task
      context->taskId = osCreateTask("Modbus/TCP Server",
         (OsTaskCode) modbusServerTask, context, &context->taskParams);
 
      //Failed to create task?
      if(context->taskId == OS_INVALID_TASK_ID)
      {
         //Report an error
         error = ERROR_OUT_OF_RESOURCES;
         break;
      }
 
      //End of exception handling block
   } while(0);
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      context->running = FALSE;
 
      //Close listening socket
      socketClose(context->socket);
      context->socket = NULL;
   }
 
   //Return status code
   return error;
}
 
 
/**
 * @brief Stop Modbus/TCP server
 * @param[in] context Pointer to the Modbus/TCP server context
 * @return Error code
 **/
 
error_t modbusServerStop(ModbusServerContext *context)
{
   uint_t i;
 
   //Make sure the Modbus/TCP server context is valid
   if(context == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Debug message
   TRACE_INFO("Stopping Modbus/TCP server...\r\n");
 
   //Check whether the Modbus/TCP server is running
   if(context->running)
   {
#if (NET_RTOS_SUPPORT == ENABLED)
      //Stop the Modbus/TCP server
      context->stop = TRUE;
      //Send a signal to the task to abort any blocking operation
      osSetEvent(&context->event);
 
      //Wait for the task to terminate
      while(context->running)
      {
         osDelayTask(1);
      }
#endif
 
      //Loop through the connection table
      for(i = 0; i < MODBUS_SERVER_MAX_CONNECTIONS; i++)
      {
         //Check the state of the current connection
         if(context->connection[i].state != MODBUS_CONNECTION_STATE_CLOSED)
         {
            //Close client connection
            modbusServerCloseConnection(&context->connection[i]);
         }
      }
 
      //Close listening socket
      socketClose(context->socket);
      context->socket = NULL;
   }
 
   //Successful processing
   return NO_ERROR;
}
 
 
/**
 * @brief Modbus/TCP server task
 * @param[in] context Pointer to the Modbus/TCP server context
 **/
 
void modbusServerTask(ModbusServerContext *context)
{
   error_t error;
   uint_t i;
   systime_t timeout;
   ModbusClientConnection *connection;
   SocketEventDesc eventDesc[MODBUS_SERVER_MAX_CONNECTIONS + 1];
 
#if (NET_RTOS_SUPPORT == ENABLED)
   //Task prologue
   osEnterTask();
 
   //Process events
   while(1)
   {
#endif
      //Set polling timeout
      timeout = MODBUS_SERVER_TICK_INTERVAL;
 
      //Clear event descriptor set
      osMemset(eventDesc, 0, sizeof(eventDesc));
 
      //Specify the events the application is interested in
      for(i = 0; i < MODBUS_SERVER_MAX_CONNECTIONS; i++)
      {
         //Point to the structure describing the current connection
         connection = &context->connection[i];
 
         //Loop through active connections only
         if(connection->state != MODBUS_CONNECTION_STATE_CLOSED)
         {
            //Register connection events
            modbusServerRegisterConnectionEvents(connection, &eventDesc[i]);
 
            //Check whether the socket is ready for I/O operation
            if(eventDesc[i].eventFlags != 0)
            {
               //No need to poll the underlying socket for incoming traffic
               timeout = 0;
            }
         }
      }
 
      //The Modbus/TCP server listens for connection requests on port 502
      eventDesc[i].socket = context->socket;
      eventDesc[i].eventMask = SOCKET_EVENT_RX_READY;
 
      //Wait for one of the set of sockets to become ready to perform I/O
      error = socketPoll(eventDesc, MODBUS_SERVER_MAX_CONNECTIONS + 1,
         &context->event, timeout);
 
      //Check status code
      if(error == NO_ERROR || error == ERROR_TIMEOUT ||
         error == ERROR_WAIT_CANCELED)
      {
         //Stop request?
         if(context->stop)
         {
            //Stop Modbus/TCP server operation
            context->running = FALSE;
            //Task epilogue
            osExitTask();
            //Kill ourselves
            osDeleteTask(OS_SELF_TASK_ID);
         }
 
         //Event-driven processing
         for(i = 0; i < MODBUS_SERVER_MAX_CONNECTIONS; i++)
         {
            //Point to the structure describing the current connection
            connection = &context->connection[i];
 
            //Loop through active connections only
            if(connection->state != MODBUS_CONNECTION_STATE_CLOSED)
            {
               //Check whether the socket is ready to perform I/O
               if(eventDesc[i].eventFlags != 0)
               {
                  //Connection event handler
                  modbusServerProcessConnectionEvents(connection);
               }
            }
         }
 
         //Any connection request received on port 502?
         if(eventDesc[i].eventFlags != 0)
         {
            //Accept connection request
            modbusServerAcceptConnection(context);
         }
      }
 
      //Handle periodic operations
      modbusServerTick(context);
 
#if (NET_RTOS_SUPPORT == ENABLED)
   }
#endif
}
 
 
/**
 * @brief Release Modbus/TCP server context
 * @param[in] context Pointer to the Modbus/TCP server context
 **/
 
void modbusServerDeinit(ModbusServerContext *context)
{
   //Make sure the Modbus/TCP server context is valid
   if(context != NULL)
   {
      //Free previously allocated resources
      osDeleteEvent(&context->event);
 
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED && TLS_TICKET_SUPPORT == ENABLED)
      //Release ticket encryption context
      tlsFreeTicketContext(&context->tlsTicketContext);
#endif
 
      //Clear Modbus/TCP server context
      osMemset(context, 0, sizeof(ModbusServerContext));
   }
}
 
#endif