libmodbus/tests/unit-test-client.c

/*
 * Copyright © 2008-2014 Stéphane Raimbault <stephane.raimbault@gmail.com>
 *
 * 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"

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);

#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 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 ireal;
    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;

    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", 1502);
    } else if (use_backend == TCP_PI) {
        ctx = modbus_new_tcp_pi("::1", "1502");
    } 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");

    printf("1/1 No response timeout modification on connect: ");
    ASSERT_TRUE(old_response_to_sec == new_response_to_sec &&
                old_response_to_usec == new_response_to_usec, "");

    /* Allocate and initialize the memory to store the bits */
    nb_points = (UT_BITS_NB > UT_INPUT_BITS_NB) ? UT_BITS_NB : UT_INPUT_BITS_NB;
    tab_rp_bits = (uint8_t *) malloc(nb_points * sizeof(uint8_t));
    memset(tab_rp_bits, 0, nb_points * sizeof(uint8_t));

    /* Allocate and initialize the memory to store the registers */
    nb_points = (UT_REGISTERS_NB > UT_INPUT_REGISTERS_NB) ?
        UT_REGISTERS_NB : UT_INPUT_REGISTERS_NB;
    tab_rp_registers = (uint16_t *) malloc(nb_points * sizeof(uint16_t));
    memset(tab_rp_registers, 0, nb_points * sizeof(uint16_t));

    printf("\nTEST WRITE/READ:\n");

    /** COIL BITS **/

    /* Single */
    rc = modbus_write_bit(ctx, UT_BITS_ADDRESS, ON);
    printf("1/2 modbus_write_bit: ");
    ASSERT_TRUE(rc == 1, "");

    rc = modbus_read_bits(ctx, UT_BITS_ADDRESS, 1, tab_rp_bits);
    printf("2/2 modbus_read_bits: ");
    ASSERT_TRUE(rc == 1, "FAILED (nb points %d)\n", rc);
    ASSERT_TRUE(tab_rp_bits[0] == ON, "FAILED (%0X != %0X)\n",
                tab_rp_bits[0], ON);

    /* End single */

    /* Multiple bits */
    {
        uint8_t tab_value[UT_BITS_NB];

        modbus_set_bits_from_bytes(tab_value, 0, UT_BITS_NB, UT_BITS_TAB);
        rc = modbus_write_bits(ctx, UT_BITS_ADDRESS,
                               UT_BITS_NB, tab_value);
        printf("1/2 modbus_write_bits: ");
        ASSERT_TRUE(rc == UT_BITS_NB, "");
    }

    rc = modbus_read_bits(ctx, UT_BITS_ADDRESS, UT_BITS_NB, tab_rp_bits);
    printf("2/2 modbus_read_bits: ");
    ASSERT_TRUE(rc == UT_BITS_NB, "FAILED (nb points %d)\n", rc);

    i = 0;
    nb_points = UT_BITS_NB;
    while (nb_points > 0) {
        int nb_bits = (nb_points > 8) ? 8 : nb_points;

        value = modbus_get_byte_from_bits(tab_rp_bits, i*8, nb_bits);
        ASSERT_TRUE(value == UT_BITS_TAB[i], "FAILED (%0X != %0X)\n",
                    value, UT_BITS_TAB[i]);

        nb_points -= nb_bits;
        i++;
    }
    printf("OK\n");
    /* End of multiple bits */

    /** DISCRETE INPUTS **/
    rc = modbus_read_input_bits(ctx, UT_INPUT_BITS_ADDRESS,
                                UT_INPUT_BITS_NB, tab_rp_bits);
    printf("1/1 modbus_read_input_bits: ");
    ASSERT_TRUE(rc == UT_INPUT_BITS_NB, "FAILED (nb points %d)\n", rc);

    i = 0;
    nb_points = UT_INPUT_BITS_NB;
    while (nb_points > 0) {
        int nb_bits = (nb_points > 8) ? 8 : nb_points;
        value = modbus_get_byte_from_bits(tab_rp_bits, i*8, nb_bits);
        ASSERT_TRUE(value == UT_INPUT_BITS_TAB[i], "FAILED (%0X != %0X)\n",
                    value, UT_INPUT_BITS_TAB[i]);

        nb_points -= nb_bits;
        i++;
    }
    printf("OK\n");

    /** HOLDING REGISTERS **/

    /* Single register */
    rc = modbus_write_register(ctx, UT_REGISTERS_ADDRESS, 0x1234);
    printf("1/2 modbus_write_register: ");
    ASSERT_TRUE(rc == 1, "");

    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                               1, tab_rp_registers);
    printf("2/2 modbus_read_registers: ");
    ASSERT_TRUE(rc == 1, "FAILED (nb points %d)\n", rc);
    ASSERT_TRUE(tab_rp_registers[0] == 0x1234, "FAILED (%0X != %0X)\n",
                tab_rp_registers[0], 0x1234);
    /* End of single register */

    /* Many registers */
    rc = modbus_write_registers(ctx, UT_REGISTERS_ADDRESS,
                                UT_REGISTERS_NB, UT_REGISTERS_TAB);
    printf("1/5 modbus_write_registers: ");
    ASSERT_TRUE(rc == UT_REGISTERS_NB, "");

    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                               UT_REGISTERS_NB, tab_rp_registers);
    printf("2/5 modbus_read_registers: ");
    ASSERT_TRUE(rc == UT_REGISTERS_NB, "FAILED (nb points %d)\n", rc);

    for (i=0; i < UT_REGISTERS_NB; i++) {
        ASSERT_TRUE(tab_rp_registers[i] == UT_REGISTERS_TAB[i],
                    "FAILED (%0X != %0X)\n",
                    tab_rp_registers[i], UT_REGISTERS_TAB[i]);
    }

    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                               0, tab_rp_registers);
    printf("3/5 modbus_read_registers (0): ");
    ASSERT_TRUE(rc == -1, "FAILED (nb_points %d)\n", rc);

    nb_points = (UT_REGISTERS_NB >
                 UT_INPUT_REGISTERS_NB) ?
        UT_REGISTERS_NB : UT_INPUT_REGISTERS_NB;
    memset(tab_rp_registers, 0, nb_points * sizeof(uint16_t));

    /* Write registers to zero from tab_rp_registers and store read registers
       into tab_rp_registers. So the read registers must set to 0, except the
       first one because there is an offset of 1 register on write. */
    rc = modbus_write_and_read_registers(ctx,
                                         UT_REGISTERS_ADDRESS + 1,
                                         UT_REGISTERS_NB - 1,
                                         tab_rp_registers,
                                         UT_REGISTERS_ADDRESS,
                                         UT_REGISTERS_NB,
                                         tab_rp_registers);
    printf("4/5 modbus_write_and_read_registers: ");
    ASSERT_TRUE(rc == UT_REGISTERS_NB, "FAILED (nb points %d != %d)\n",
                rc, UT_REGISTERS_NB);

    ASSERT_TRUE(tab_rp_registers[0] == UT_REGISTERS_TAB[0],
                "FAILED (%0X != %0X)\n",
                tab_rp_registers[0], UT_REGISTERS_TAB[0]);

    for (i=1; i < UT_REGISTERS_NB; i++) {
        ASSERT_TRUE(tab_rp_registers[i] == 0, "FAILED (%0X != %0X)\n",
                    tab_rp_registers[i], 0);
    }

    /* End of many registers */


    /** INPUT REGISTERS **/
    rc = modbus_read_input_registers(ctx, UT_INPUT_REGISTERS_ADDRESS,
                                     UT_INPUT_REGISTERS_NB,
                                     tab_rp_registers);
    printf("1/1 modbus_read_input_registers: ");
    ASSERT_TRUE(rc == UT_INPUT_REGISTERS_NB, "FAILED (nb points %d)\n", rc);

    for (i=0; i < UT_INPUT_REGISTERS_NB; i++) {
        ASSERT_TRUE(tab_rp_registers[i] == UT_INPUT_REGISTERS_TAB[i],
                    "FAILED (%0X != %0X)\n",
                    tab_rp_registers[i], UT_INPUT_REGISTERS_TAB[i]);
    }

    printf("\nTEST FLOATS\n");
    /** FLOAT **/
    printf("1/4 Set float: ");
    modbus_set_float(UT_REAL, tab_rp_registers);
    if (tab_rp_registers[1] == (UT_IREAL >> 16) &&
        tab_rp_registers[0] == (UT_IREAL & 0xFFFF)) {
        printf("OK\n");
    } else {
        /* Avoid *((uint32_t *)tab_rp_registers)
         * https://github.com/stephane/libmodbus/pull/104 */
        ireal = (uint32_t) tab_rp_registers[0] & 0xFFFF;
        ireal |= (uint32_t) tab_rp_registers[1] << 16;
        printf("FAILED (%x != %x)\n", ireal, UT_IREAL);
        goto close;
    }

    printf("2/4 Get float: ");
    real = modbus_get_float(tab_rp_registers);
    ASSERT_TRUE(real == UT_REAL, "FAILED (%f != %f)\n", real, UT_REAL);

    printf("3/4 Set float in DBCA order: ");
    modbus_set_float_dcba(UT_REAL, tab_rp_registers);
    ireal = (uint32_t) tab_rp_registers[0] & 0xFFFF;
    ireal |= (uint32_t) tab_rp_registers[1] << 16;
    ASSERT_TRUE(tab_rp_registers[1] == (UT_IREAL_DCBA >> 16) &&
                tab_rp_registers[0] == (UT_IREAL_DCBA & 0xFFFF),
                "FAILED (%x != %x)\n", ireal, UT_IREAL_DCBA);

    printf("4/4 Get float in DCBA order: ");
    real = modbus_get_float_dcba(tab_rp_registers);
    ASSERT_TRUE(real == UT_REAL, "FAILED (%f != %f)\n", real, UT_REAL);

    /* MASKS */
    printf("1/1 Write mask: ");
    rc = modbus_write_register(ctx, UT_REGISTERS_ADDRESS, 0x12);
    rc = modbus_mask_write_register(ctx, UT_REGISTERS_ADDRESS, 0xF2, 0x25);
    ASSERT_TRUE(rc != -1, "FAILED (%x == -1)\n", rc);
    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS, 1, tab_rp_registers);
    ASSERT_TRUE(tab_rp_registers[0] == 0x17,
                "FAILED (%0X != %0X)\n",
                tab_rp_registers[0], 0x17);

    printf("\nAt this point, error messages doesn't mean the test has failed\n");

    /** ILLEGAL DATA ADDRESS **/
    printf("\nTEST ILLEGAL DATA ADDRESS:\n");

    /* The mapping begins at 0 and ends at address + nb_points so
     * the addresses are not valid. */

    rc = modbus_read_bits(ctx, UT_BITS_ADDRESS, UT_BITS_NB + 1, tab_rp_bits);
    printf("* modbus_read_bits: ");
    ASSERT_TRUE(rc == -1 && errno == EMBXILADD, "");

    rc = modbus_read_input_bits(ctx, UT_INPUT_BITS_ADDRESS,
                                UT_INPUT_BITS_NB + 1, tab_rp_bits);
    printf("* modbus_read_input_bits: ");
    ASSERT_TRUE(rc == -1 && errno == EMBXILADD, "");

    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                               UT_REGISTERS_NB + 1, tab_rp_registers);
    printf("* modbus_read_registers: ");
    ASSERT_TRUE(rc == -1 && errno == EMBXILADD, "");

    rc = modbus_read_input_registers(ctx, UT_INPUT_REGISTERS_ADDRESS,
                                     UT_INPUT_REGISTERS_NB + 1,
                                     tab_rp_registers);
    printf("* modbus_read_input_registers: ");
    ASSERT_TRUE(rc == -1 && errno == EMBXILADD, "");

    rc = modbus_write_bit(ctx, UT_BITS_ADDRESS + UT_BITS_NB, ON);
    printf("* modbus_write_bit: ");
    ASSERT_TRUE(rc == -1 && errno == EMBXILADD, "");

    rc = modbus_write_bits(ctx, UT_BITS_ADDRESS + UT_BITS_NB,
                           UT_BITS_NB, tab_rp_bits);
    printf("* modbus_write_coils: ");
    ASSERT_TRUE(rc == -1 && errno == EMBXILADD, "");

    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS + UT_REGISTERS_NB,
                               UT_REGISTERS_NB, tab_rp_registers);
    printf("* modbus_write_registers: ");
    ASSERT_TRUE(rc == -1 && errno == EMBXILADD, "");

    /** TOO MANY DATA **/
    printf("\nTEST TOO MANY DATA ERROR:\n");

    rc = modbus_read_bits(ctx, UT_BITS_ADDRESS,
                          MODBUS_MAX_READ_BITS + 1, tab_rp_bits);
    printf("* modbus_read_bits: ");
    ASSERT_TRUE(rc == -1 && errno == EMBMDATA, "");

    rc = modbus_read_input_bits(ctx, UT_INPUT_BITS_ADDRESS,
                                MODBUS_MAX_READ_BITS + 1, tab_rp_bits);
    printf("* modbus_read_input_bits: ");
    ASSERT_TRUE(rc == -1 && errno == EMBMDATA, "");

    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                               MODBUS_MAX_READ_REGISTERS + 1,
                               tab_rp_registers);
    printf("* modbus_read_registers: ");
    ASSERT_TRUE(rc == -1 && errno == EMBMDATA, "");

    rc = modbus_read_input_registers(ctx, UT_INPUT_REGISTERS_ADDRESS,
                                     MODBUS_MAX_READ_REGISTERS + 1,
                                     tab_rp_registers);
    printf("* modbus_read_input_registers: ");
    ASSERT_TRUE(rc == -1 && errno == EMBMDATA, "");

    rc = modbus_write_bits(ctx, UT_BITS_ADDRESS,
                           MODBUS_MAX_WRITE_BITS + 1, tab_rp_bits);
    printf("* modbus_write_bits: ");
    ASSERT_TRUE(rc == -1 && errno == EMBMDATA, "");

    rc = modbus_write_registers(ctx, UT_REGISTERS_ADDRESS,
                                MODBUS_MAX_WRITE_REGISTERS + 1,
                                tab_rp_registers);
    printf("* modbus_write_registers: ");
    ASSERT_TRUE(rc == -1 && errno == EMBMDATA, "");

    /** SLAVE REPLY **/
    printf("\nTEST SLAVE REPLY:\n");
    modbus_set_slave(ctx, INVALID_SERVER_ID);
    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                               UT_REGISTERS_NB, tab_rp_registers);
    if (use_backend == RTU) {
        const int RAW_REQ_LENGTH = 6;
        uint8_t raw_req[] = { INVALID_SERVER_ID, 0x03, 0x00, 0x01, 0x01, 0x01 };
        /* Too many points */
        uint8_t raw_invalid_req[] = { INVALID_SERVER_ID, 0x03, 0x00, 0x01, 0xFF, 0xFF };
        const int RAW_REP_LENGTH = 7;
        uint8_t raw_rep[] = { INVALID_SERVER_ID, 0x03, 0x04, 0, 0, 0, 0 };
        uint8_t rsp[MODBUS_RTU_MAX_ADU_LENGTH];

        /* No response in RTU mode */
        printf("1-A/3 No response from slave %d: ", INVALID_SERVER_ID);
        ASSERT_TRUE(rc == -1 && errno == ETIMEDOUT, "");

        /* The slave raises a timeout on a confirmation to ignore because if an
         * indication for another slave is received, a confirmation must follow */


        /* Send a pair of indication/confirmation to the slave with a different
         * slave ID to simulate a communication on a RS485 bus. At first, the
         * slave will see the indication message then the confirmation, and it must
         * ignore both. */
        modbus_send_raw_request(ctx, raw_req, RAW_REQ_LENGTH * sizeof(uint8_t));
        modbus_send_raw_request(ctx, raw_rep, RAW_REP_LENGTH * sizeof(uint8_t));
        rc = modbus_receive_confirmation(ctx, rsp);

        printf("1-B/3 No response from slave %d on indication/confirmation messages: ",
               INVALID_SERVER_ID);
        ASSERT_TRUE(rc == -1 && errno == ETIMEDOUT, "");

        /* Send an INVALID request for another slave */
        modbus_send_raw_request(ctx, raw_invalid_req, RAW_REQ_LENGTH * sizeof(uint8_t));
        rc = modbus_receive_confirmation(ctx, rsp);

        printf("1-C/3 No response from slave %d with invalid request: ",
               INVALID_SERVER_ID);
        ASSERT_TRUE(rc == -1 && errno == ETIMEDOUT, "");
    } else {
        /* Response in TCP mode */
        printf("1/3 Response from slave %d: ", INVALID_SERVER_ID);
        ASSERT_TRUE(rc == UT_REGISTERS_NB, "");
    }

    rc = modbus_set_slave(ctx, MODBUS_BROADCAST_ADDRESS);
    ASSERT_TRUE(rc != -1, "Invalid broacast address");

    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                               UT_REGISTERS_NB, tab_rp_registers);
    printf("2/3 No reply after a broadcast query: ");
    ASSERT_TRUE(rc == -1 && errno == ETIMEDOUT, "");

    /* Restore slave */
    if (use_backend == RTU) {
        modbus_set_slave(ctx, SERVER_ID);
    } else {
        modbus_set_slave(ctx, MODBUS_TCP_SLAVE);
    }

    printf("3/3 Response with an invalid TID or slave: ");
    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS_INVALID_TID_OR_SLAVE,
                               1, tab_rp_registers);
    ASSERT_TRUE(rc == -1, "");

    printf("1/2 Report slave ID truncated: \n");
    /* Set a marker to ensure limit is respected */
    tab_rp_bits[NB_REPORT_SLAVE_ID - 1] = 42;
    rc = modbus_report_slave_id(ctx, NB_REPORT_SLAVE_ID - 1, tab_rp_bits);
    /* Return the size required (response size) but respects the defined limit */
    ASSERT_TRUE(rc == NB_REPORT_SLAVE_ID &&
                tab_rp_bits[NB_REPORT_SLAVE_ID - 1] == 42,
                "Return is rc %d (%d) and marker is %d (42)",
                rc, NB_REPORT_SLAVE_ID, tab_rp_bits[NB_REPORT_SLAVE_ID - 1]);

    printf("2/2 Report slave ID: \n");
    /* tab_rp_bits is used to store bytes */
    rc = modbus_report_slave_id(ctx, NB_REPORT_SLAVE_ID, tab_rp_bits);
    ASSERT_TRUE(rc == NB_REPORT_SLAVE_ID, "");

    /* Slave ID is an arbitraty number for libmodbus */
    ASSERT_TRUE(rc > 0, "");

    /* Run status indicator is ON */
    ASSERT_TRUE(rc > 1 && tab_rp_bits[1] == 0xFF, "");

    /* Print additional data as string */
    if (rc > 2) {
        printf("Additional data: ");
        for (i=2; i < rc; i++) {
            printf("%c", tab_rp_bits[i]);
        }
        printf("\n");
    }

    /* Save original timeout */
    modbus_get_response_timeout(ctx, &old_response_to_sec, &old_response_to_usec);
    modbus_get_byte_timeout(ctx, &old_byte_to_sec, &old_byte_to_usec);

    rc = modbus_set_response_timeout(ctx, 0, 0);
    printf("1/6 Invalid response timeout (zero): ");
    ASSERT_TRUE(rc == -1 && errno == EINVAL, "");

    rc = modbus_set_response_timeout(ctx, 0, 1000000);
    printf("2/6 Invalid response timeout (too large us): ");
    ASSERT_TRUE(rc == -1 && errno == EINVAL, "");

    rc = modbus_set_byte_timeout(ctx, 0, 1000000);
    printf("3/6 Invalid byte timeout (too large us): ");
    ASSERT_TRUE(rc == -1 && errno == EINVAL, "");

    modbus_set_response_timeout(ctx, 0, 1);
    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                               UT_REGISTERS_NB, tab_rp_registers);
    printf("4/6 1us response timeout: ");
    if (rc == -1 && errno == ETIMEDOUT) {
        printf("OK\n");
    } else {
        printf("FAILED (can fail on some platforms)\n");
    }

    /* A wait and flush operation is done by the error recovery code of
     * libmodbus but after a sleep of current response timeout
     * so 0 can be too short!
     */
    usleep(old_response_to_sec * 1000000 + old_response_to_usec);
    modbus_flush(ctx);

    /* Trigger a special behaviour on server to wait for 0.5 second before
     * replying whereas allowed timeout is 0.2 second */
    modbus_set_response_timeout(ctx, 0, 200000);
    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS_SLEEP_500_MS,
                               1, tab_rp_registers);
    printf("5/6 Too short response timeout (0.2s < 0.5s): ");
    ASSERT_TRUE(rc == -1 && errno == ETIMEDOUT, "");

    /* Wait for reply (0.2 + 0.4 > 0.5 s) and flush before continue */
    usleep(400000);
    modbus_flush(ctx);

    modbus_set_response_timeout(ctx, 0, 600000);
    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS_SLEEP_500_MS,
                               1, tab_rp_registers);
    printf("6/6 Adequate response timeout (0.6s > 0.5s): ");
    ASSERT_TRUE(rc == 1, "");

    /* Disable the byte timeout.
       The full response must be available in the 600ms interval */
    modbus_set_byte_timeout(ctx, 0, 0);
    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS_SLEEP_500_MS,
                               1, tab_rp_registers);
    printf("7/7 Disable byte timeout: ");
    ASSERT_TRUE(rc == 1, "");

    /* Restore original response timeout */
    modbus_set_response_timeout(ctx, old_response_to_sec,
                                old_response_to_usec);

    if (use_backend == TCP) {
        /* The test server is only able to test byte timeouts with the TCP
         * backend */

        /* Timeout of 3ms between bytes */
        modbus_set_byte_timeout(ctx, 0, 3000);
        rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS_BYTE_SLEEP_5_MS,
                                   1, tab_rp_registers);
        printf("1/2 Too small byte timeout (3ms < 5ms): ");
        ASSERT_TRUE(rc == -1 && errno == ETIMEDOUT, "");

        /* Wait remaing bytes before flushing */
        usleep(11 * 5000);
        modbus_flush(ctx);

        /* Timeout of 7ms between bytes */
        modbus_set_byte_timeout(ctx, 0, 7000);
        rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS_BYTE_SLEEP_5_MS,
                                   1, tab_rp_registers);
        printf("2/2 Adapted byte timeout (7ms > 5ms): ");
        ASSERT_TRUE(rc == 1, "");
    }

    /* Restore original byte timeout */
    modbus_set_byte_timeout(ctx, old_byte_to_sec, old_byte_to_usec);

    /** BAD RESPONSE **/
    printf("\nTEST BAD RESPONSE ERROR:\n");

    /* Allocate only the required space */
    tab_rp_registers_bad = (uint16_t *) malloc(
        UT_REGISTERS_NB_SPECIAL * sizeof(uint16_t));

    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                               UT_REGISTERS_NB_SPECIAL, tab_rp_registers_bad);
    printf("* modbus_read_registers: ");
    ASSERT_TRUE(rc == -1 && errno == EMBBADDATA, "");
    free(tab_rp_registers_bad);

    /** MANUAL EXCEPTION **/
    printf("\nTEST MANUAL EXCEPTION:\n");
    rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS_SPECIAL,
                               UT_REGISTERS_NB, tab_rp_registers);

    printf("* modbus_read_registers at special address: ");
    ASSERT_TRUE(rc == -1 && errno == EMBXSBUSY, "");

    /** SERVER **/
    if (test_server(ctx, use_backend) == -1) {
        goto close;
    }

    /* Test init functions */
    printf("\nTEST INVALID INITIALIZATION:\n");
    ctx = modbus_new_rtu(NULL, 1, 'A', 0, 0);
    ASSERT_TRUE(ctx == NULL && errno == EINVAL, "");

    ctx = modbus_new_rtu("/dev/dummy", 0, 'A', 0, 0);
    ASSERT_TRUE(ctx == NULL && errno == EINVAL, "");

    ctx = modbus_new_tcp_pi(NULL, NULL);
    ASSERT_TRUE(ctx == NULL && errno == EINVAL, "");

    printf("\nALL TESTS PASS WITH SUCCESS.\n");
    success = TRUE;

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;
    uint8_t read_raw_req[] = {
        /* slave */
        (use_backend == RTU) ? SERVER_ID : 0xFF,
        /* function, addr 1, 5 values */
        MODBUS_FC_READ_HOLDING_REGISTERS, 0x00, 0x01, 0x0, 0x05
    };
    /* Write and read registers request */
    const int RW_RAW_REQ_LEN = 13;
    uint8_t rw_raw_req[] = {
        /* slave */
        (use_backend == RTU) ? SERVER_ID : 0xFF,
        /* function, addr to read, nb to read */
        MODBUS_FC_WRITE_AND_READ_REGISTERS,
        /* Read */
        0, 0,
        (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 */
        (use_backend == RTU) ? SERVER_ID : 0xFF,
        /* 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
    };
    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");

    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;

    return 0;
close:
    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)
{
    const int EXCEPTION_RC = 2;
    uint8_t rsp[MODBUS_TCP_MAX_ADU_LENGTH];
    int j;
    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);

    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, "");
    }
    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;
}