open_source / modbus

  #pragma once

  
  #define _MODBUS_TCP_HEADER_LENGTH      7
  #define _MODBUS_TCP_PRESET_REQ_LENGTH 12
  #define _MODBUS_TCP_PRESET_RSP_LENGTH  8
  
  #define _MODBUS_TCP_CHECKSUM_LENGTH    0
  
  /* In both structures, the transaction ID must be placed on first position
     to have a quick access not dependant of the TCP backend */

  typedef struct _modbus_tcp 
  {

      /* Extract from MODBUS Messaging on TCP/IP Implementation Guide V1.0b
         (page 23/46):
         The transaction identifier is used to associate the future response
         with the request. This identifier is unique on each TCP connection. */
      uint16_t t_id;
      /* TCP port */
      int port;
      /* IP address */
      char ip[16];
  } modbus_tcp_t;
  
  #define _MODBUS_TCP_PI_NODE_LENGTH    1025
  #define _MODBUS_TCP_PI_SERVICE_LENGTH   32
  

  typedef struct _modbus_tcp_pi 
  {

      /* Transaction ID */
      uint16_t t_id;
      /* TCP port */
      int port;
      /* Node */
      char node[_MODBUS_TCP_PI_NODE_LENGTH];
      /* Service */
      char service[_MODBUS_TCP_PI_SERVICE_LENGTH];
  } modbus_tcp_pi_t;