modbus_server.h

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/**
 * @file modbus_server.h
 * @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 2.6.6
 **/
 
#ifndef _MODBUS_SERVER_H
#define _MODBUS_SERVER_H
 
//Dependencies
#include "core/net.h"
#include "modbus/modbus_common.h"
 
//Modbus/TCP server support
#ifndef MODBUS_SERVER_SUPPORT
   #define MODBUS_SERVER_SUPPORT ENABLED
#elif (MODBUS_SERVER_SUPPORT != ENABLED && MODBUS_SERVER_SUPPORT != DISABLED)
   #error MODBUS_SERVER_SUPPORT parameter is not valid
#endif
 
//Modbus/TCP security
#ifndef MODBUS_SERVER_TLS_SUPPORT
   #define MODBUS_SERVER_TLS_SUPPORT DISABLED
#elif (MODBUS_SERVER_TLS_SUPPORT != ENABLED && MODBUS_SERVER_TLS_SUPPORT != DISABLED)
   #error MODBUS_SERVER_TLS_SUPPORT parameter is not valid
#endif
 
//Modbus diagnostics
#ifndef MODBUS_SERVER_DIAG_SUPPORT
   #define MODBUS_SERVER_DIAG_SUPPORT DISABLED
#elif (MODBUS_SERVER_DIAG_SUPPORT != ENABLED && MODBUS_SERVER_DIAG_SUPPORT != DISABLED)
   #error MODBUS_SERVER_DIAG_SUPPORT parameter is not valid
#endif
 
//Stack size required to run the Modbus/TCP server
#ifndef MODBUS_SERVER_STACK_SIZE
   #define MODBUS_SERVER_STACK_SIZE 650
#elif (MODBUS_SERVER_STACK_SIZE < 1)
   #error MODBUS_SERVER_STACK_SIZE parameter is not valid
#endif
 
//Priority at which the Modbus/TCP server should run
#ifndef MODBUS_SERVER_PRIORITY
   #define MODBUS_SERVER_PRIORITY OS_TASK_PRIORITY_NORMAL
#endif
 
//Maximum number of simultaneous connections
#ifndef MODBUS_SERVER_MAX_CONNECTIONS
   #define MODBUS_SERVER_MAX_CONNECTIONS 2
#elif (MODBUS_SERVER_MAX_CONNECTIONS < 1)
   #error MODBUS_SERVER_MAX_CONNECTIONS parameter is not valid
#endif
 
//Idle connection timeout
#ifndef MODBUS_SERVER_TIMEOUT
   #define MODBUS_SERVER_TIMEOUT 60000
#elif (MODBUS_SERVER_TIMEOUT < 1000)
   #error MODBUS_SERVER_TIMEOUT parameter is not valid
#endif
 
//Modbus/TCP server tick interval
#ifndef MODBUS_SERVER_TICK_INTERVAL
   #define MODBUS_SERVER_TICK_INTERVAL 1000
#elif (MODBUS_SERVER_TICK_INTERVAL < 100)
   #error MODBUS_SERVER_TICK_INTERVAL parameter is not valid
#endif
 
//TX buffer size for TLS connections
#ifndef MODBUS_SERVER_TLS_TX_BUFFER_SIZE
   #define MODBUS_SERVER_TLS_TX_BUFFER_SIZE 2048
#elif (MODBUS_SERVER_TLS_TX_BUFFER_SIZE < 512)
   #error MODBUS_SERVER_TLS_TX_BUFFER_SIZE parameter is not valid
#endif
 
//RX buffer size for TLS connections
#ifndef MODBUS_SERVER_TLS_RX_BUFFER_SIZE
   #define MODBUS_SERVER_TLS_RX_BUFFER_SIZE 2048
#elif (MODBUS_SERVER_TLS_RX_BUFFER_SIZE < 512)
   #error MODBUS_SERVER_TLS_RX_BUFFER_SIZE parameter is not valid
#endif
 
//Maximum length of the client role OID
#ifndef MODBUS_SERVER_MAX_ROLE_LEN
   #define MODBUS_SERVER_MAX_ROLE_LEN 32
#elif (MODBUS_SERVER_MAX_ROLE_LEN < 0)
   #error MODBUS_SERVER_MAX_ROLE_LEN parameter is not valid
#endif
 
//Application specific context
#ifndef MODBUS_SERVER_CONTEXT_PRIVATE
   #define MODBUS_SERVER_CONTEXT_PRIVATE
#endif
 
//TLS supported?
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED)
   #include "core/crypto.h"
   #include "tls/tls.h"
   #include "tls/tls_ticket.h"
#endif
 
//Forward declaration of ModbusServerContext structure
struct _ModbusServerContext;
#define ModbusServerContext struct _ModbusServerContext
 
//Forward declaration of ModbusClientConnection structure
struct _ModbusClientConnection;
#define ModbusClientConnection struct _ModbusClientConnection
 
//C++ guard
#ifdef __cplusplus
extern "C" {
#endif
 
 
/**
 * @brief Modbus/TCP connection state
 **/
 
typedef enum
{
   MODBUS_CONNECTION_STATE_CLOSED       = 0,
   MODBUS_CONNECTION_STATE_CONNECT_TLS  = 1,
   MODBUS_CONNECTION_STATE_RECEIVE      = 2,
   MODBUS_CONNECTION_STATE_SEND         = 3,
   MODBUS_CONNECTION_STATE_SHUTDOWN_TLS = 4,
   MODBUS_CONNECTION_STATE_SHUTDOWN_TX  = 5,
   MODBUS_CONNECTION_STATE_SHUTDOWN_RX  = 6
} ModbusConnectionState;
 
 
/**
 * @brief TCP connection open callback function
 **/
 
typedef error_t (*ModbusServerOpenCallback)(ModbusClientConnection *connection,
   IpAddr clientIpAddr, uint16_t clientPort);
 
 
/**
 * @brief TCP connection close callback function
 **/
 
typedef void (*ModbusServerCloseCallback)(ModbusClientConnection *connection);
 
 
//TLS supported?
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED)
 
/**
 * @brief TLS initialization callback function
 **/
 
typedef error_t (*ModbusServerTlsInitCallback)
   (ModbusClientConnection *connection, TlsContext *tlsContext);
 
#endif
 
 
/**
 * @brief Lock Modbus table callback function
 **/
 
typedef void (*ModbusServerLockCallback)(ModbusClientConnection *connection);
 
 
/**
 * @brief Unlock Modbus table callback function
 **/
 
typedef void (*ModbusServerUnlockCallback)(ModbusClientConnection *connection);
 
 
/**
 * @brief Get coil state callback function
 **/
 
typedef error_t (*ModbusServerReadCoilCallback)(ModbusClientConnection *connection,
   uint16_t address, bool_t *state);
 
 
/**
 * @brief Set coil state callback function
 **/
 
typedef error_t (*ModbusServerWriteCoilCallback)(ModbusClientConnection *connection,
   uint16_t address, bool_t state, bool_t commit);
 
 
/**
 * @brief Get register value callback function
 **/
 
typedef error_t (*ModbusServerReadRegCallback)(ModbusClientConnection *connection,
   uint16_t address, uint16_t *value);
 
 
/**
 * @brief Set register value callback function
 **/
 
typedef error_t (*ModbusServerWriteRegCallback)(ModbusClientConnection *connection,
   uint16_t address, uint16_t value, bool_t commit);
 
 
/**
 * @brief PDU processing callback function
 **/
 
typedef error_t (*ModbusServerProcessPduCallback)(ModbusClientConnection *connection,
   const uint8_t *request, size_t requestLen, uint8_t *response,
   size_t *responseLen);
 
 
/**
 * @brief Tick callback function
 **/
 
typedef void (*ModbusServerTickCallback)(ModbusServerContext *context);
 
 
/**
 * @brief Modbus/TCP server settings
 **/
 
typedef struct
{
   OsTaskParameters task;                                  ///<Task parameters
   NetContext *netContext;                                 ///<TCP/IP stack context
   NetInterface *interface;                                ///<Underlying network interface
   uint16_t port;                                          ///<Modbus/TCP port number
   uint8_t unitId;                                         ///<Unit identifier
   systime_t timeout;                                      ///<Idle connection timeout
   ModbusServerOpenCallback openCallback;                  ///<TCP connection open callback function
   ModbusServerCloseCallback closeCallback;                ///<TCP connection close callback function
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED)
   ModbusServerTlsInitCallback tlsInitCallback;            ///<TLS initialization callback function
#endif
   ModbusServerLockCallback lockCallback;                  ///<Lock Modbus table callback function
   ModbusServerUnlockCallback unlockCallback;              ///<Unlock Modbus table callback function
   ModbusServerReadCoilCallback readCoilCallback;          ///<Get coil state callback function
   ModbusServerReadCoilCallback readDiscreteInputCallback; ///<Get discrete input state callback function
   ModbusServerWriteCoilCallback writeCoilCallback;        ///<Set coil state callback function
   ModbusServerReadRegCallback readRegCallback;            ///<Get register value callback function
   ModbusServerReadRegCallback readHoldingRegCallback;     ///<Get holding register value callback function
   ModbusServerReadRegCallback readInputRegCallback;       ///<Get input register value callback function
   ModbusServerWriteRegCallback writeRegCallback;          ///<Set register value callback function
   ModbusServerProcessPduCallback processPduCallback;      ///<PDU processing callback function
   ModbusServerTickCallback tickCallback;                  ///<Tick callback function
} ModbusServerSettings;
 
 
/**
 * @brief Modbus/TCP client connection
 **/
 
struct _ModbusClientConnection
{
   ModbusConnectionState state;                 ///<Connection state
   ModbusServerContext *context;                ///<Modbus/TCP server context
   Socket *socket;                              ///<Underlying socket
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED)
   TlsContext *tlsContext;                      ///<TLS context
#endif
   char_t role[MODBUS_SERVER_MAX_ROLE_LEN + 1]; ///<Client role OID
   systime_t timestamp;                         ///<Time stamp
   uint8_t requestAdu[MODBUS_MAX_ADU_SIZE];     ///<Request ADU
   size_t requestAduLen;                        ///<Length of the request ADU, in bytes
   size_t requestAduPos;                        ///<Current position in the request ADU
   uint8_t requestUnitId;                       ///<Unit identifier
   uint8_t responseAdu[MODBUS_MAX_ADU_SIZE];    ///<Response ADU
   size_t responseAduLen;                       ///<Length of the response ADU, in bytes
   size_t responseAduPos;                       ///<Current position in the response ADU
};
 
 
/**
 * @brief Modbus/TCP server context
 **/
 
struct _ModbusServerContext
{
   NetContext *netContext;                                 ///<TCP/IP stack context
   NetInterface *interface;                                ///<Underlying network interface
   uint16_t port;                                          ///<Modbus/TCP port number
   uint8_t unitId;                                         ///<Unit identifier
   systime_t timeout;                                      ///<Idle connection timeout
   ModbusServerOpenCallback openCallback;                  ///<TCP connection open callback function
   ModbusServerCloseCallback closeCallback;                ///<TCP connection close callback function
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED)
   ModbusServerTlsInitCallback tlsInitCallback;            ///<TLS initialization callback function
#endif
   ModbusServerLockCallback lockCallback;                  ///<Lock Modbus table callback function
   ModbusServerUnlockCallback unlockCallback;              ///<Unlock Modbus table callback function
   ModbusServerReadCoilCallback readCoilCallback;          ///<Get coil state callback function
   ModbusServerReadCoilCallback readDiscreteInputCallback; ///<Get discrete input state callback function
   ModbusServerWriteCoilCallback writeCoilCallback;        ///<Set coil state callback function
   ModbusServerReadRegCallback readRegCallback;            ///<Get register value callback function
   ModbusServerReadRegCallback readHoldingRegCallback;     ///<Get holding register value callback function
   ModbusServerReadRegCallback readInputRegCallback;       ///<Get input register value callback function
   ModbusServerWriteRegCallback writeRegCallback;          ///<Set register value callback function
   ModbusServerProcessPduCallback processPduCallback;      ///<PDU processing callback function
   ModbusServerTickCallback tickCallback;                  ///<Tick callback function
   bool_t running;                                         ///<Operational state of the Modbus/TCP server
   bool_t stop;                                            ///<Stop request
   OsEvent event;                                          ///<Event object used to poll the sockets
   OsTaskParameters taskParams;                            ///<Task parameters
   OsTaskId taskId;                                        ///<Task identifier
   Socket *socket;                                         ///<Listening socket
   ModbusClientConnection connection[MODBUS_SERVER_MAX_CONNECTIONS]; ///<Client connections
#if (MODBUS_SERVER_TLS_SUPPORT == ENABLED && TLS_TICKET_SUPPORT == ENABLED)
   TlsTicketContext tlsTicketContext;                      ///<TLS ticket encryption context
#endif
#if (MODBUS_SERVER_DIAG_SUPPORT == ENABLED)
   uint32_t rxMessageCount;                                ///<Total number of messages received
   uint32_t txMessageCount;                                ///<Total number of messages sent
   uint32_t commErrorCount;                                ///<Total number of communication errors
   uint32_t exceptionErrorCount;                           ///<Total number of exception errors
#endif
   MODBUS_SERVER_CONTEXT_PRIVATE                           ///<Application specific context
};
 
 
//Modbus/TCP server related functions
void modbusServerGetDefaultSettings(ModbusServerSettings *settings);
 
error_t modbusServerInit(ModbusServerContext *context,
   const ModbusServerSettings *settings);
 
error_t modbusServerStart(ModbusServerContext *context);
error_t modbusServerStop(ModbusServerContext *context);
 
void modbusServerTask(ModbusServerContext *context);
 
void modbusServerDeinit(ModbusServerContext *context);
 
//C++ guard
#ifdef __cplusplus
}
#endif
 
#endif