debian man page for modbus_send_raw_request

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, 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.

RETURN VALUE
       The modbus_send_raw_request() 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, 0x03, 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
", 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 Stephane Raimbault <stephane.raimbault@gmail.com[1]>

NOTES
	1. stephane.raimbault@gmail.com
	   mailto:stephane.raimbault@gmail.com

libmodbus 3.0.3 						    05/26/2012						   MODBUS_SEND_RAW_REQU(3)