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MODBUS_SEND_RAW_REQU(3)	       libmodbus Manual	       MODBUS_SEND_RAW_REQU(3)

NAME
       modbus_send_raw_request - send a	raw request

SYNOPSIS
       int modbus_send_raw_request(modbus_t *ctx, const	uint8_t	*raw_req, int
       raw_req_length);

DESCRIPTION
       The modbus_send_raw_request() function shall send a request via the
       socket of the context ctx. This function	must be	used for debugging
       purposes	because	you have to take care to make a	valid request by hand.
       The function only adds to the message, the header or CRC	of the
       selected	backend, so raw_req must start and contain at least a
       slave/unit identifier and a function code. This function	can be used to
       send request not	handled	by the library.

       The public header of libmodbus provides a list of supported Modbus
       functions codes,	prefixed by MODBUS_FC_ (eg.
       MODBUS_FC_READ_HOLDING_REGISTERS), to help build	of raw requests.

RETURN VALUE
       The function shall return the full message length, counting the extra
       data relating to	the backend, if	successful. Otherwise it shall return
       -1 and set errno.

EXAMPLE
	   modbus_t *ctx;
	   /* Read 5 holding registers from address 1 */
	   uint8_t raw_req[] = { 0xFF, MODBUS_FC_READ_HOLDING_REGISTERS, 0x00, 0x01, 0x0, 0x05 };
	   int req_length;
	   uint8_t rsp[MODBUS_TCP_MAX_ADU_LENGTH];

	   ctx = modbus_new_tcp("127.0.0.1", 1502);
	   if (modbus_connect(ctx) == -1) {
	       fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
	       modbus_free(ctx);
	       return -1;
	   }

	   req_length =	modbus_send_raw_request(ctx, raw_req, 6	* sizeof(uint8_t));
	   modbus_receive_confirmation(ctx, rsp);

	   modbus_close(ctx);
	   modbus_free(ctx);

SEE ALSO
       modbus_receive_confirmation(3)

AUTHORS
       The libmodbus documentation was written by StA(C)phane Raimbault
       <stephane.raimbault@gmail.com>

libmodbus v3.1.6		  08/10/2020	       MODBUS_SEND_RAW_REQU(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | EXAMPLE | SEE ALSO | AUTHORS

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