Esp32 modbus tcp slave

#define BUF_SIZE 128

/* local variables */
static uint8_t ucMbTCPRxBuf[BUF_SIZE];
static uint8_t ucMbTCPTxBuf[BUF_SIZE];

/* modbus tcp slave context */
static MbsTCPSlaveCtx_t mbsSlaveCtx;

/* modbus tcp slave port */
static MbsTCPPort_t mbsSlavePort = {
    /* ucTCPSrvPort */ 502,
    /* pxMBTCPSlaveReceive */ &ucMbTCPRxBuf,
    /* pxMBTCPSlaveSend */ &ucMbTCPTxBuf,
    /* usTCPSlaveRecvBufSize */ BUF_SIZE,
    /* usTCPSlaveSendBufSize */ BUF_SIZE,
    /* ucTCPSlaveMaxConcurrentClients */ 1
};

/* modbus tcp slave config */
static MbsTCPConfig_t mbsSlaveConfig = {