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modbus_send_raw_request(3) [debian man page]

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)

Check Out this Related Man Page

MODBUS_REPORT_SLAVE_(3) 					 Libmodbus Manual					   MODBUS_REPORT_SLAVE_(3)

NAME

       modbus_report_slave_id - returns a description of the controller

SYNOPSIS

       int modbus_report_slave_id(modbus_t *ctx, uint8_t *dest);

DESCRIPTION

       The modbus_report_slave_id() function shall send a request to the controller to obtain a description of the controller.

       The response stored in dest contains:

       o   the byte count of the response

       o   the slave ID, this unique ID is in reality not unique at all so it's not possible to depend on it to know how the information are
	   packed in the response.

       o   the run indicator status (0x00 = OFF, 0xFF = ON)

       o   additional data specific to each controller. For example, libmodbus returns the version of the library as a string.

RETURN VALUE

       The modbus_report_slave_id() function shall return the number of read data if successful. Otherwise it shall return -1 and set errno.

EXAMPLE

	   uint8_t *tab_bytes;

	   ...

	   rc = modbus_report_slave_id(ctx, tab_bytes);
	   if (rc > 1) {
	       printf("Run Status Indicator: %s
", tab_bytes[1] ? "ON" : "OFF");
	   }

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_REPORT_SLAVE_(3)
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