I am trying to create a modbus master slave model. I have written modbus slave using pymodbus and modbus master is using c libmodbus.
Slave is having a bunch of register set and register 0 is having value as
register 0, number of register 2, type hex, value 45565345
register 2, number of register 4, type hex, value 10002
I am using modbus over TCP
Below is the c code
/*
* Copyright © 2008-2014 Stéphane Raimbault <[email protected]>
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <modbus.h>
#include "unit-test.h"
const int EXCEPTION_RC = 2;
enum {
TCP,
TCP_PI,
RTU
};
int test_server(modbus_t *ctx, int use_backend);
int send_crafted_request(modbus_t *ctx, int function,
uint8_t *req, int req_size,
uint16_t max_value, uint16_t bytes,
int backend_length, int backend_offset);
int equal_dword(uint16_t *tab_reg, const uint32_t value);
#define BUG_REPORT(_cond, _format, _args ...) \
printf("\nLine %d: assertion error for '%s': " _format "\n", __LINE__, # _cond, ## _args)
#define ASSERT_TRUE(_cond, _format, __args...) { \
if (_cond) { \
printf("OK\n"); \
} else { \
BUG_REPORT(_cond, _format, ## __args); \
goto close; \
} \
};
int equal_dword(uint16_t *tab_reg, const uint32_t value) {
return ((tab_reg[0] == (value >> 16)) && (tab_reg[1] == (value & 0xFFFF)));
}
int main(int argc, char *argv[])
{
const int NB_REPORT_SLAVE_ID = 10;
uint8_t *tab_rp_bits = NULL;
uint16_t *tab_rp_registers = NULL;
uint16_t *tab_rp_registers_bad = NULL;
modbus_t *ctx = NULL;
int i;
uint8_t value;
int nb_points;
int rc;
float real;
uint32_t old_response_to_sec;
uint32_t old_response_to_usec;
uint32_t new_response_to_sec;
uint32_t new_response_to_usec;
uint32_t old_byte_to_sec;
uint32_t old_byte_to_usec;
int use_backend;
int success = FALSE;
int old_slave;
if (argc > 1) {
if (strcmp(argv[1], "tcp") == 0) {
use_backend = TCP;
} else if (strcmp(argv[1], "tcppi") == 0) {
use_backend = TCP_PI;
} else if (strcmp(argv[1], "rtu") == 0) {
use_backend = RTU;
} else {
printf("Usage:\n %s [tcp|tcppi|rtu] - Modbus client for unit testing\n\n", argv[0]);
exit(1);
}
} else {
/* By default */
use_backend = TCP;
}
if (use_backend == TCP) {
ctx = modbus_new_tcp("127.0.0.1", 1520);
} else if (use_backend == TCP_PI) {
ctx = modbus_new_tcp_pi("::1", "1520");
} else {
ctx = modbus_new_rtu("/dev/ttyUSB1", 115200, 'N', 8, 1);
}
if (ctx == NULL) {
fprintf(stderr, "Unable to allocate libmodbus context\n");
return -1;
}
modbus_set_debug(ctx, TRUE);
modbus_set_error_recovery(ctx,
MODBUS_ERROR_RECOVERY_LINK |
MODBUS_ERROR_RECOVERY_PROTOCOL);
if (use_backend == RTU) {
modbus_set_slave(ctx, SERVER_ID);
}
modbus_get_response_timeout(ctx, &old_response_to_sec, &old_response_to_usec);
if (modbus_connect(ctx) == -1) {
fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
modbus_free(ctx);
return -1;
}
modbus_get_response_timeout(ctx, &new_response_to_sec, &new_response_to_usec);
printf("** UNIT TESTING **\n");
rc = modbus_read_registers(ctx, 0x02,
2, tab_rp_registers);
printf(" value %d" , tab_rp_registers[0]);
modbus_close(ctx);
modbus_free(ctx);
ctx = NULL;
close:
/* Free the memory */
free(tab_rp_bits);
free(tab_rp_registers);
/* Close the connection */
modbus_close(ctx);
modbus_free(ctx);
return (success) ? 0 : -1;
}
/* Send crafted requests to test server resilience
and ensure proper exceptions are returned. */
int test_server(modbus_t *ctx, int use_backend)
{
int rc;
int i;
/* Read requests */
const int READ_RAW_REQ_LEN = 6;
const int slave = (use_backend == RTU) ? SERVER_ID : MODBUS_TCP_SLAVE;
uint8_t read_raw_req[] = {
slave,
/* function, address, 5 values */
MODBUS_FC_READ_HOLDING_REGISTERS,
UT_REGISTERS_ADDRESS >> 8, UT_REGISTERS_ADDRESS & 0xFF,
0x0, 0x05
};
/* Write and read registers request */
const int RW_RAW_REQ_LEN = 13;
uint8_t rw_raw_req[] = {
slave,
/* function, addr to read, nb to read */
MODBUS_FC_WRITE_AND_READ_REGISTERS,
/* Read */
UT_REGISTERS_ADDRESS >> 8, UT_REGISTERS_ADDRESS & 0xFF,
(MODBUS_MAX_WR_READ_REGISTERS + 1) >> 8,
(MODBUS_MAX_WR_READ_REGISTERS + 1) & 0xFF,
/* Write */
0, 0,
0, 1,
/* Write byte count */
1 * 2,
/* One data to write... */
0x12, 0x34
};
const int WRITE_RAW_REQ_LEN = 13;
uint8_t write_raw_req[] = {
slave,
/* function will be set in the loop */
MODBUS_FC_WRITE_MULTIPLE_REGISTERS,
/* Address */
UT_REGISTERS_ADDRESS >> 8, UT_REGISTERS_ADDRESS & 0xFF,
/* 3 values, 6 bytes */
0x00, 0x03, 0x06,
/* Dummy data to write */
0x02, 0x2B, 0x00, 0x01, 0x00, 0x64
};
const int INVALID_FC = 0x42;
const int INVALID_FC_REQ_LEN = 6;
uint8_t invalid_fc_raw_req[] = {
slave, 0x42, 0x00, 0x00, 0x00, 0x00
};
int req_length;
uint8_t rsp[MODBUS_TCP_MAX_ADU_LENGTH];
int tab_read_function[] = {
MODBUS_FC_READ_COILS,
MODBUS_FC_READ_DISCRETE_INPUTS,
MODBUS_FC_READ_HOLDING_REGISTERS,
MODBUS_FC_READ_INPUT_REGISTERS
};
int tab_read_nb_max[] = {
MODBUS_MAX_READ_BITS + 1,
MODBUS_MAX_READ_BITS + 1,
MODBUS_MAX_READ_REGISTERS + 1,
MODBUS_MAX_READ_REGISTERS + 1
};
int backend_length;
int backend_offset;
if (use_backend == RTU) {
backend_length = 3;
backend_offset = 1;
} else {
backend_length = 7;
backend_offset = 7;
}
printf("\nTEST RAW REQUESTS:\n");
uint32_t old_response_to_sec;
uint32_t old_response_to_usec;
/* This requests can generate flushes server side so we need a higher
* response timeout than the server. The server uses the defined response
* timeout to sleep before flushing.
* The old timeouts are restored at the end.
*/
modbus_get_response_timeout(ctx, &old_response_to_sec, &old_response_to_usec);
modbus_set_response_timeout(ctx, 0, 600000);
req_length = modbus_send_raw_request(ctx, read_raw_req, READ_RAW_REQ_LEN);
printf("* modbus_send_raw_request: ");
ASSERT_TRUE(req_length == (backend_length + 5), "FAILED (%d)\n", req_length);
printf("* modbus_receive_confirmation: ");
rc = modbus_receive_confirmation(ctx, rsp);
ASSERT_TRUE(rc == (backend_length + 12), "FAILED (%d)\n", rc);
/* Try to read more values than a response could hold for all data
types. */
for (i=0; i<4; i++) {
rc = send_crafted_request(ctx, tab_read_function[i],
read_raw_req, READ_RAW_REQ_LEN,
tab_read_nb_max[i], 0,
backend_length, backend_offset);
if (rc == -1)
goto close;
}
/* Modbus write and read multiple registers */
rc = send_crafted_request(ctx, MODBUS_FC_WRITE_AND_READ_REGISTERS,
rw_raw_req, RW_RAW_REQ_LEN,
MODBUS_MAX_WR_READ_REGISTERS + 1, 0,
backend_length, backend_offset);
if (rc == -1)
goto close;
/* Modbus write multiple registers with large number of values but a set a
small number of bytes in requests (not nb * 2 as usual). */
rc = send_crafted_request(ctx, MODBUS_FC_WRITE_MULTIPLE_REGISTERS,
write_raw_req, WRITE_RAW_REQ_LEN,
MODBUS_MAX_WRITE_REGISTERS + 1, 6,
backend_length, backend_offset);
if (rc == -1)
goto close;
rc = send_crafted_request(ctx, MODBUS_FC_WRITE_MULTIPLE_COILS,
write_raw_req, WRITE_RAW_REQ_LEN,
MODBUS_MAX_WRITE_BITS + 1, 6,
backend_length, backend_offset);
if (rc == -1)
goto close;
/* Test invalid function code */
modbus_send_raw_request(ctx, invalid_fc_raw_req, INVALID_FC_REQ_LEN * sizeof(uint8_t));
rc = modbus_receive_confirmation(ctx, rsp);
printf("Return an exception on unknown function code: ");
ASSERT_TRUE(rc == (backend_length + EXCEPTION_RC) &&
rsp[backend_offset] == (0x80 + INVALID_FC), "")
modbus_set_response_timeout(ctx, old_response_to_sec, old_response_to_usec);
return 0;
close:
modbus_set_response_timeout(ctx, old_response_to_sec, old_response_to_usec);
return -1;
}
int send_crafted_request(modbus_t *ctx, int function,
uint8_t *req, int req_len,
uint16_t max_value, uint16_t bytes,
int backend_length, int backend_offset)
{
uint8_t rsp[MODBUS_TCP_MAX_ADU_LENGTH];
int j;
for (j=0; j<2; j++) {
int rc;
req[1] = function;
if (j == 0) {
/* Try to read or write zero values on first iteration */
req[4] = 0x00;
req[5] = 0x00;
if (bytes) {
/* Write query */
req[6] = 0x00;
}
} else {
/* Try to read or write max values + 1 on second iteration */
req[4] = (max_value >> 8) & 0xFF;
req[5] = max_value & 0xFF;
if (bytes) {
/* Write query (nb values * 2 to convert in bytes for registers) */
req[6] = bytes;
}
}
modbus_send_raw_request(ctx, req, req_len * sizeof(uint8_t));
if (j == 0) {
printf("* try function 0x%X: %s 0 values: ", function, bytes ? "write": "read");
} else {
printf("* try function 0x%X: %s %d values: ", function, bytes ? "write": "read",
max_value);
}
rc = modbus_receive_confirmation(ctx, rsp);
ASSERT_TRUE(rc == (backend_length + EXCEPTION_RC) &&
rsp[backend_offset] == (0x80 + function) &&
rsp[backend_offset + 1] == MODBUS_EXCEPTION_ILLEGAL_DATA_VALUE, "");
}
return 0;
close:
return -1;
}
I am getting below output from modbus master
Connecting to 127.0.0.1:1520
** UNIT TESTING **
[00][01][00][00][00][06][FF][03][00][02][00][02]
Waiting for a confirmation...
<00><01><00><00><00><07><FF><03><04><00><01><00><02>
Segmentation fault (core dumped)
Output on modbus slave
DEBUG:pymodbus.server.async:Client Connected [IPv4Address(type='TCP', host='127.0.0.1', port=1520)]
DEBUG:pymodbus.server.async:Data Received: 0x0 0x1 0x0 0x0 0x0 0x6 0xff 0x3 0x0 0x2 0x0 0x2
DEBUG:pymodbus.framer.socket_framer:Processing: 0x0 0x1 0x0 0x0 0x0 0x6 0xff 0x3 0x0 0x2 0x0 0x2
DEBUG:pymodbus.factory:Factory Request[3]
DEBUG:pymodbus.datastore.context:validate[3] 3:2
DEBUG:pymodbus.datastore.context:getValues[3] 3:2
DEBUG:pymodbus.datastore.context:xxxxxxxxxxxxxxxxxxxxxxxxx
DEBUG:pymodbus.datastore.context:[1, 2]
DEBUG:pymodbus.server.async:send: 000100000007ff030400010002
DEBUG:pymodbus.server.async:Client Disconnected: [Failure instance: Traceback (failure with no frames): <class 'twisted.internet.error.ConnectionDone'>: Connection was closed cleanly.
I am trying to retrieve value of the register. Not sure why I am not getting the value
