First working commit

src/main.cpp

@@ -0,0 +1,8 @@
+#include <iostream>
+
+int main(){
+
+    std::cout << "Hello world";
+
+    return 0;
+}

src/modbus-data.c

@@ -0,0 +1,292 @@
+/*
+ * Copyright © Stéphane Raimbault <stephane.raimbault@gmail.com>
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#include <stdlib.h>
+
+// clang-format off
+#ifndef _MSC_VER
+#  include <stdint.h>
+#else
+#  include "stdint.h"
+#endif
+
+#include <string.h>
+#include <assert.h>
+
+#if defined(_WIN32)
+#  include <winsock2.h>
+#else
+#  include <arpa/inet.h>
+#endif
+
+#include <config.h>
+
+#include "modbus.h"
+
+#if defined(HAVE_BYTESWAP_H)
+#  include <byteswap.h>
+#endif
+
+#if defined(__APPLE__)
+#  include <libkern/OSByteOrder.h>
+#  define bswap_16 OSSwapInt16
+#  define bswap_32 OSSwapInt32
+#  define bswap_64 OSSwapInt64
+#endif
+
+#if defined(__GNUC__)
+#  define GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__ * 10)
+#  if GCC_VERSION >= 430
+// Since GCC >= 4.30, GCC provides __builtin_bswapXX() alternatives so we switch to them
+#    undef bswap_32
+#    define bswap_32 __builtin_bswap32
+#  endif
+#  if GCC_VERSION >= 480
+#    undef bswap_16
+#    define bswap_16 __builtin_bswap16
+#  endif
+#endif
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1400)
+#  define bswap_32 _byteswap_ulong
+#  define bswap_16 _byteswap_ushort
+#endif
+
+#if !defined(bswap_16)
+#  warning "Fallback on C functions for bswap_16"
+static inline uint16_t bswap_16(uint16_t x)
+{
+    return (x >> 8) | (x << 8);
+}
+#endif
+
+#if !defined(bswap_32)
+#  warning "Fallback on C functions for bswap_32"
+static inline uint32_t bswap_32(uint32_t x)
+{
+    return (bswap_16(x & 0xffff) << 16) | (bswap_16(x >> 16));
+}
+#endif
+// clang-format on
+
+/* Sets many bits from a single byte value (all 8 bits of the byte value are
+   set) */
+void modbus_set_bits_from_byte(uint8_t *dest, int idx, const uint8_t value)
+{
+    int i;
+
+    for (i = 0; i < 8; i++) {
+        dest[idx + i] = (value & (1 << i)) ? 1 : 0;
+    }
+}
+
+/* Sets many bits from a table of bytes (only the bits between idx and
+   idx + nb_bits are set) */
+void modbus_set_bits_from_bytes(uint8_t *dest,
+                                int idx,
+                                unsigned int nb_bits,
+                                const uint8_t *tab_byte)
+{
+    unsigned int i;
+    int shift = 0;
+
+    for (i = idx; i < idx + nb_bits; i++) {
+        dest[i] = tab_byte[(i - idx) / 8] & (1 << shift) ? 1 : 0;
+        /* gcc doesn't like: shift = (++shift) % 8; */
+        shift++;
+        shift %= 8;
+    }
+}
+
+/* Gets the byte value from many bits.
+   To obtain a full byte, set nb_bits to 8. */
+uint8_t modbus_get_byte_from_bits(const uint8_t *src, int idx, unsigned int nb_bits)
+{
+    unsigned int i;
+    uint8_t value = 0;
+
+    if (nb_bits > 8) {
+        /* Assert is ignored if NDEBUG is set */
+        assert(nb_bits < 8);
+        nb_bits = 8;
+    }
+
+    for (i = 0; i < nb_bits; i++) {
+        value |= (src[idx + i] << i);
+    }
+
+    return value;
+}
+
+/* Get a float from 4 bytes (Modbus) without any conversion (ABCD) */
+float modbus_get_float_abcd(const uint16_t *src)
+{
+    float f;
+    uint32_t i;
+    uint8_t a, b, c, d;
+
+    a = (src[0] >> 8) & 0xFF;
+    b = (src[0] >> 0) & 0xFF;
+    c = (src[1] >> 8) & 0xFF;
+    d = (src[1] >> 0) & 0xFF;
+
+    i = (a << 24) | (b << 16) | (c << 8) | (d << 0);
+    memcpy(&f, &i, 4);
+
+    return f;
+}
+
+/* Get a float from 4 bytes (Modbus) in inversed format (DCBA) */
+float modbus_get_float_dcba(const uint16_t *src)
+{
+    float f;
+    uint32_t i;
+    uint8_t a, b, c, d;
+
+    a = (src[0] >> 8) & 0xFF;
+    b = (src[0] >> 0) & 0xFF;
+    c = (src[1] >> 8) & 0xFF;
+    d = (src[1] >> 0) & 0xFF;
+
+    i = (d << 24) | (c << 16) | (b << 8) | (a << 0);
+    memcpy(&f, &i, 4);
+
+    return f;
+}
+
+/* Get a float from 4 bytes (Modbus) with swapped bytes (BADC) */
+float modbus_get_float_badc(const uint16_t *src)
+{
+    float f;
+    uint32_t i;
+    uint8_t a, b, c, d;
+
+    a = (src[0] >> 8) & 0xFF;
+    b = (src[0] >> 0) & 0xFF;
+    c = (src[1] >> 8) & 0xFF;
+    d = (src[1] >> 0) & 0xFF;
+
+    i = (b << 24) | (a << 16) | (d << 8) | (c << 0);
+    memcpy(&f, &i, 4);
+
+    return f;
+}
+
+/* Get a float from 4 bytes (Modbus) with swapped words (CDAB) */
+float modbus_get_float_cdab(const uint16_t *src)
+{
+    float f;
+    uint32_t i;
+    uint8_t a, b, c, d;
+
+    a = (src[0] >> 8) & 0xFF;
+    b = (src[0] >> 0) & 0xFF;
+    c = (src[1] >> 8) & 0xFF;
+    d = (src[1] >> 0) & 0xFF;
+
+    i = (c << 24) | (d << 16) | (a << 8) | (b << 0);
+    memcpy(&f, &i, 4);
+
+    return f;
+}
+
+/* DEPRECATED - Get a float from 4 bytes in sort of Modbus format */
+float modbus_get_float(const uint16_t *src)
+{
+    float f;
+    uint32_t i;
+
+    i = (((uint32_t) src[1]) << 16) + src[0];
+    memcpy(&f, &i, sizeof(float));
+
+    return f;
+}
+
+/* Set a float to 4 bytes for Modbus w/o any conversion (ABCD) */
+void modbus_set_float_abcd(float f, uint16_t *dest)
+{
+    uint32_t i;
+    uint8_t *out = (uint8_t *) dest;
+    uint8_t a, b, c, d;
+
+    memcpy(&i, &f, sizeof(uint32_t));
+    a = (i >> 24) & 0xFF;
+    b = (i >> 16) & 0xFF;
+    c = (i >> 8) & 0xFF;
+    d = (i >> 0) & 0xFF;
+
+    out[0] = a;
+    out[1] = b;
+    out[2] = c;
+    out[3] = d;
+}
+
+/* Set a float to 4 bytes for Modbus with byte and word swap conversion (DCBA) */
+void modbus_set_float_dcba(float f, uint16_t *dest)
+{
+    uint32_t i;
+    uint8_t *out = (uint8_t *) dest;
+    uint8_t a, b, c, d;
+
+    memcpy(&i, &f, sizeof(uint32_t));
+    a = (i >> 24) & 0xFF;
+    b = (i >> 16) & 0xFF;
+    c = (i >> 8) & 0xFF;
+    d = (i >> 0) & 0xFF;
+
+    out[0] = d;
+    out[1] = c;
+    out[2] = b;
+    out[3] = a;
+}
+
+/* Set a float to 4 bytes for Modbus with byte swap conversion (BADC) */
+void modbus_set_float_badc(float f, uint16_t *dest)
+{
+    uint32_t i;
+    uint8_t *out = (uint8_t *) dest;
+    uint8_t a, b, c, d;
+
+    memcpy(&i, &f, sizeof(uint32_t));
+    a = (i >> 24) & 0xFF;
+    b = (i >> 16) & 0xFF;
+    c = (i >> 8) & 0xFF;
+    d = (i >> 0) & 0xFF;
+
+    out[0] = b;
+    out[1] = a;
+    out[2] = d;
+    out[3] = c;
+}
+
+/* Set a float to 4 bytes for Modbus with word swap conversion (CDAB) */
+void modbus_set_float_cdab(float f, uint16_t *dest)
+{
+    uint32_t i;
+    uint8_t *out = (uint8_t *) dest;
+    uint8_t a, b, c, d;
+
+    memcpy(&i, &f, sizeof(uint32_t));
+    a = (i >> 24) & 0xFF;
+    b = (i >> 16) & 0xFF;
+    c = (i >> 8) & 0xFF;
+    d = (i >> 0) & 0xFF;
+
+    out[0] = c;
+    out[1] = d;
+    out[2] = a;
+    out[3] = b;
+}
+
+/* DEPRECATED - Set a float to 4 bytes in a sort of Modbus format! */
+void modbus_set_float(float f, uint16_t *dest)
+{
+    uint32_t i;
+
+    memcpy(&i, &f, sizeof(uint32_t));
+    dest[0] = (uint16_t) i;
+    dest[1] = (uint16_t) (i >> 16);
+}

src/modbus-tcp.c

@@ -0,0 +1,974 @@
+/*
+ * Copyright © Stéphane Raimbault <stephane.raimbault@gmail.com>
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+// clang-format off
+#if defined(_WIN32)
+# define OS_WIN32
+/* ws2_32.dll has getaddrinfo and freeaddrinfo on Windows XP and later.
+ * minwg32 headers check WINVER before allowing the use of these */
+# ifndef WINVER
+#   define WINVER 0x0501
+# endif
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#ifndef _MSC_VER
+#include <unistd.h>
+#endif
+#include <signal.h>
+#include <sys/types.h>
+
+#if defined(_WIN32)
+/* Already set in modbus-tcp.h but it seems order matters in VS2005 */
+# include <winsock2.h>
+# include <ws2tcpip.h>
+# define SHUT_RDWR 2
+# define close closesocket
+# define strdup _strdup
+#else
+# include <sys/socket.h>
+# include <sys/ioctl.h>
+
+#if defined(__OpenBSD__) || (defined(__FreeBSD__) && __FreeBSD__ < 5)
+# define OS_BSD
+# include <netinet/in_systm.h>
+#endif
+
+# include <netinet/in.h>
+# include <netinet/ip.h>
+# include <netinet/tcp.h>
+# include <arpa/inet.h>
+# include <netdb.h>
+#endif
+
+#if !defined(MSG_NOSIGNAL)
+#define MSG_NOSIGNAL 0
+#endif
+
+#if defined(_AIX) && !defined(MSG_DONTWAIT)
+#define MSG_DONTWAIT MSG_NONBLOCK
+#endif
+// clang-format on
+
+#include "modbus-private.h"
+
+#include "modbus-tcp-private.h"
+#include "modbus-tcp.h"
+
+#ifdef OS_WIN32
+static int _modbus_tcp_init_win32(void)
+{
+    /* Initialise Windows Socket API */
+    WSADATA wsaData;
+
+    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
+        fprintf(stderr,
+                "WSAStartup() returned error code %d\n",
+                (unsigned int) GetLastError());
+        errno = EIO;
+        return -1;
+    }
+    return 0;
+}
+#endif
+
+static int _modbus_set_slave(modbus_t *ctx, int slave)
+{
+    int max_slave = (ctx->quirks & MODBUS_QUIRK_MAX_SLAVE) ? 255 : 247;
+
+    /* Broadcast address is 0 (MODBUS_BROADCAST_ADDRESS) */
+    if (slave >= 0 && slave <= max_slave) {
+        ctx->slave = slave;
+    } else if (slave == MODBUS_TCP_SLAVE) {
+        /* The special value MODBUS_TCP_SLAVE (0xFF) can be used in TCP mode to
+         * restore the default value. */
+        ctx->slave = slave;
+    } else {
+        errno = EINVAL;
+        return -1;
+    }
+
+    return 0;
+}
+
+/* Builds a TCP request header */
+static int _modbus_tcp_build_request_basis(
+    modbus_t *ctx, int function, int addr, int nb, uint8_t *req)
+{
+    modbus_tcp_t *ctx_tcp = ctx->backend_data;
+
+    /* Increase transaction ID */
+    if (ctx_tcp->t_id < UINT16_MAX)
+        ctx_tcp->t_id++;
+    else
+        ctx_tcp->t_id = 0;
+    req[0] = ctx_tcp->t_id >> 8;
+    req[1] = ctx_tcp->t_id & 0x00ff;
+
+    /* Protocol Modbus */
+    req[2] = 0;
+    req[3] = 0;
+
+    /* Length will be defined later by set_req_length_tcp at offsets 4
+       and 5 */
+
+    req[6] = ctx->slave;
+    req[7] = function;
+    req[8] = addr >> 8;
+    req[9] = addr & 0x00ff;
+    req[10] = nb >> 8;
+    req[11] = nb & 0x00ff;
+
+    return _MODBUS_TCP_PRESET_REQ_LENGTH;
+}
+
+/* Builds a TCP response header */
+static int _modbus_tcp_build_response_basis(sft_t *sft, uint8_t *rsp)
+{
+    /* Extract from MODBUS Messaging on TCP/IP Implementation
+       Guide V1.0b (page 23/46):
+       The transaction identifier is used to associate the future
+       response with the request. */
+    rsp[0] = sft->t_id >> 8;
+    rsp[1] = sft->t_id & 0x00ff;
+
+    /* Protocol Modbus */
+    rsp[2] = 0;
+    rsp[3] = 0;
+
+    /* Length will be set later by send_msg (4 and 5) */
+
+    /* The slave ID is copied from the indication */
+    rsp[6] = sft->slave;
+    rsp[7] = sft->function;
+
+    return _MODBUS_TCP_PRESET_RSP_LENGTH;
+}
+
+static int _modbus_tcp_prepare_response_tid(const uint8_t *req, int *req_length)
+{
+    return (req[0] << 8) + req[1];
+}
+
+static int _modbus_tcp_send_msg_pre(uint8_t *req, int req_length)
+{
+    /* Subtract the header length to the message length */
+    int mbap_length = req_length - 6;
+
+    req[4] = mbap_length >> 8;
+    req[5] = mbap_length & 0x00FF;
+
+    return req_length;
+}
+
+static ssize_t _modbus_tcp_send(modbus_t *ctx, const uint8_t *req, int req_length)
+{
+    /* MSG_NOSIGNAL
+       Requests not to send SIGPIPE on errors on stream oriented
+       sockets when the other end breaks the connection.  The EPIPE
+       error is still returned. */
+    return send(ctx->s, (const char *) req, req_length, MSG_NOSIGNAL);
+}
+
+static int _modbus_tcp_receive(modbus_t *ctx, uint8_t *req)
+{
+    return _modbus_receive_msg(ctx, req, MSG_INDICATION);
+}
+
+static ssize_t _modbus_tcp_recv(modbus_t *ctx, uint8_t *rsp, int rsp_length)
+{
+    return recv(ctx->s, (char *) rsp, rsp_length, 0);
+}
+
+static int _modbus_tcp_check_integrity(modbus_t *ctx, uint8_t *msg, const int msg_length)
+{
+    return msg_length;
+}
+
+static int _modbus_tcp_pre_check_confirmation(modbus_t *ctx,
+                                              const uint8_t *req,
+                                              const uint8_t *rsp,
+                                              int rsp_length)
+{
+    unsigned int protocol_id;
+    /* Check transaction ID */
+    if (req[0] != rsp[0] || req[1] != rsp[1]) {
+        if (ctx->debug) {
+            fprintf(stderr,
+                    "Invalid transaction ID received 0x%X (not 0x%X)\n",
+                    (rsp[0] << 8) + rsp[1],
+                    (req[0] << 8) + req[1]);
+        }
+        errno = EMBBADDATA;
+        return -1;
+    }
+
+    /* Check protocol ID */
+    protocol_id = (rsp[2] << 8) + rsp[3];
+    if (protocol_id != 0x0) {
+        if (ctx->debug) {
+            fprintf(stderr, "Invalid protocol ID received 0x%X (not 0x0)\n", protocol_id);
+        }
+        errno = EMBBADDATA;
+        return -1;
+    }
+
+    return 0;
+}
+
+static int _modbus_tcp_set_ipv4_options(int s)
+{
+    int rc;
+    int option;
+
+    /* Set the TCP no delay flag */
+    /* SOL_TCP = IPPROTO_TCP */
+    option = 1;
+    rc = setsockopt(s, IPPROTO_TCP, TCP_NODELAY, (const void *) &option, sizeof(int));
+    if (rc == -1) {
+        return -1;
+    }
+
+    /* If the OS does not offer SOCK_NONBLOCK, fall back to setting FIONBIO to
+     * make sockets non-blocking */
+    /* Do not care about the return value, this is optional */
+#if !defined(SOCK_NONBLOCK) && defined(FIONBIO)
+#ifdef OS_WIN32
+    {
+        /* Setting FIONBIO expects an unsigned long according to MSDN */
+        u_long loption = 1;
+        ioctlsocket(s, FIONBIO, &loption);
+    }
+#else
+    option = 1;
+    ioctl(s, FIONBIO, &option);
+#endif
+#endif
+
+#ifndef OS_WIN32
+    /**
+     * Cygwin defines IPTOS_LOWDELAY but can't handle that flag so it's
+     * necessary to workaround that problem.
+     **/
+    /* Set the IP low delay option */
+    option = IPTOS_LOWDELAY;
+    rc = setsockopt(s, IPPROTO_IP, IP_TOS, (const void *) &option, sizeof(int));
+    if (rc == -1) {
+        return -1;
+    }
+#endif
+
+    return 0;
+}
+
+static int _connect(int sockfd,
+                    const struct sockaddr *addr,
+                    socklen_t addrlen,
+                    const struct timeval *ro_tv)
+{
+    int rc = connect(sockfd, addr, addrlen);
+
+#ifdef OS_WIN32
+    int wsaError = 0;
+    if (rc == -1) {
+        wsaError = WSAGetLastError();
+    }
+
+    if (wsaError == WSAEWOULDBLOCK || wsaError == WSAEINPROGRESS) {
+#else
+    if (rc == -1 && errno == EINPROGRESS) {
+#endif
+        fd_set wset;
+        int optval;
+        socklen_t optlen = sizeof(optval);
+        struct timeval tv = *ro_tv;
+
+        /* Wait to be available in writing */
+        FD_ZERO(&wset);
+        FD_SET(sockfd, &wset);
+        rc = select(sockfd + 1, NULL, &wset, NULL, &tv);
+        if (rc <= 0) {
+            /* Timeout or fail */
+            return -1;
+        }
+
+        /* The connection is established if SO_ERROR and optval are set to 0 */
+        rc = getsockopt(sockfd, SOL_SOCKET, SO_ERROR, (void *) &optval, &optlen);
+        if (rc == 0 && optval == 0) {
+            return 0;
+        } else {
+            errno = ECONNREFUSED;
+            return -1;
+        }
+    }
+    return rc;
+}
+
+/* Establishes a modbus TCP connection with a Modbus server. */
+static int _modbus_tcp_connect(modbus_t *ctx)
+{
+    int rc;
+    /* Specialized version of sockaddr for Internet socket address (same size) */
+    struct sockaddr_in addr;
+    modbus_tcp_t *ctx_tcp = ctx->backend_data;
+    int flags = SOCK_STREAM;
+
+#ifdef OS_WIN32
+    if (_modbus_tcp_init_win32() == -1) {
+        return -1;
+    }
+#endif
+
+#ifdef SOCK_CLOEXEC
+    flags |= SOCK_CLOEXEC;
+#endif
+
+#ifdef SOCK_NONBLOCK
+    flags |= SOCK_NONBLOCK;
+#endif
+
+    ctx->s = socket(PF_INET, flags, 0);
+    if (ctx->s < 0) {
+        return -1;
+    }
+
+    rc = _modbus_tcp_set_ipv4_options(ctx->s);
+    if (rc == -1) {
+        close(ctx->s);
+        ctx->s = -1;
+        return -1;
+    }
+
+    if (ctx->debug) {
+        printf("Connecting to %s:%d\n", ctx_tcp->ip, ctx_tcp->port);
+    }
+
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(ctx_tcp->port);
+    rc = inet_pton(addr.sin_family, ctx_tcp->ip, &(addr.sin_addr));
+    if (rc <= 0) {
+        if (ctx->debug) {
+            fprintf(stderr, "Invalid IP address: %s\n", ctx_tcp->ip);
+        }
+        close(ctx->s);
+        ctx->s = -1;
+        return -1;
+    }
+
+    rc =
+        _connect(ctx->s, (struct sockaddr *) &addr, sizeof(addr), &ctx->response_timeout);
+    if (rc == -1) {
+        close(ctx->s);
+        ctx->s = -1;
+        return -1;
+    }
+
+    return 0;
+}
+
+/* Establishes a modbus TCP PI connection with a Modbus server. */
+static int _modbus_tcp_pi_connect(modbus_t *ctx)
+{
+    int rc;
+    struct addrinfo *ai_list;
+    struct addrinfo *ai_ptr;
+    struct addrinfo ai_hints;
+    modbus_tcp_pi_t *ctx_tcp_pi = ctx->backend_data;
+
+#ifdef OS_WIN32
+    if (_modbus_tcp_init_win32() == -1) {
+        return -1;
+    }
+#endif
+
+    memset(&ai_hints, 0, sizeof(ai_hints));
+#ifdef AI_ADDRCONFIG
+    ai_hints.ai_flags |= AI_ADDRCONFIG;
+#endif
+    ai_hints.ai_family = AF_UNSPEC;
+    ai_hints.ai_socktype = SOCK_STREAM;
+    ai_hints.ai_addr = NULL;
+    ai_hints.ai_canonname = NULL;
+    ai_hints.ai_next = NULL;
+
+    ai_list = NULL;
+    rc = getaddrinfo(ctx_tcp_pi->node, ctx_tcp_pi->service, &ai_hints, &ai_list);
+    if (rc != 0) {
+        if (ctx->debug) {
+            fprintf(stderr, "Error returned by getaddrinfo: %s\n", gai_strerror(rc));
+        }
+        errno = ECONNREFUSED;
+        return -1;
+    }
+
+    for (ai_ptr = ai_list; ai_ptr != NULL; ai_ptr = ai_ptr->ai_next) {
+        int flags = ai_ptr->ai_socktype;
+        int s;
+
+#ifdef SOCK_CLOEXEC
+        flags |= SOCK_CLOEXEC;
+#endif
+
+#ifdef SOCK_NONBLOCK
+        flags |= SOCK_NONBLOCK;
+#endif
+
+        s = socket(ai_ptr->ai_family, flags, ai_ptr->ai_protocol);
+        if (s < 0)
+            continue;
+
+        if (ai_ptr->ai_family == AF_INET)
+            _modbus_tcp_set_ipv4_options(s);
+
+        if (ctx->debug) {
+            printf("Connecting to [%s]:%s\n", ctx_tcp_pi->node, ctx_tcp_pi->service);
+        }
+
+        rc = _connect(s, ai_ptr->ai_addr, ai_ptr->ai_addrlen, &ctx->response_timeout);
+        if (rc == -1) {
+            close(s);
+            continue;
+        }
+
+        ctx->s = s;
+        break;
+    }
+
+    freeaddrinfo(ai_list);
+
+    if (ctx->s < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static unsigned int _modbus_tcp_is_connected(modbus_t *ctx)
+{
+    return ctx->s >= 0;
+}
+
+/* Closes the network connection and socket in TCP mode */
+static void _modbus_tcp_close(modbus_t *ctx)
+{
+    if (ctx->s >= 0) {
+        shutdown(ctx->s, SHUT_RDWR);
+        close(ctx->s);
+        ctx->s = -1;
+    }
+}
+
+static int _modbus_tcp_flush(modbus_t *ctx)
+{
+    int rc;
+    int rc_sum = 0;
+
+    do {
+        /* Extract the garbage from the socket */
+        char devnull[MODBUS_TCP_MAX_ADU_LENGTH];
+#ifndef OS_WIN32
+        rc = recv(ctx->s, devnull, MODBUS_TCP_MAX_ADU_LENGTH, MSG_DONTWAIT);
+#else
+        /* On Win32, it's a bit more complicated to not wait */
+        fd_set rset;
+        struct timeval tv;
+
+        tv.tv_sec = 0;
+        tv.tv_usec = 0;
+        FD_ZERO(&rset);
+        FD_SET(ctx->s, &rset);
+        rc = select(ctx->s + 1, &rset, NULL, NULL, &tv);
+        if (rc == -1) {
+            return -1;
+        }
+
+        if (rc == 1) {
+            /* There is data to flush */
+            rc = recv(ctx->s, devnull, MODBUS_TCP_MAX_ADU_LENGTH, 0);
+        }
+#endif
+        if (rc > 0) {
+            rc_sum += rc;
+        }
+    } while (rc == MODBUS_TCP_MAX_ADU_LENGTH);
+
+    return rc_sum;
+}
+
+/* Listens for any request from one or many modbus masters in TCP */
+int modbus_tcp_listen(modbus_t *ctx, int nb_connection)
+{
+    int new_s;
+    int enable;
+    int flags;
+    struct sockaddr_in addr;
+    modbus_tcp_t *ctx_tcp;
+    int rc;
+
+    if (ctx == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    ctx_tcp = ctx->backend_data;
+
+#ifdef OS_WIN32
+    if (_modbus_tcp_init_win32() == -1) {
+        return -1;
+    }
+#endif
+
+    flags = SOCK_STREAM;
+
+#ifdef SOCK_CLOEXEC
+    flags |= SOCK_CLOEXEC;
+#endif
+
+    new_s = socket(PF_INET, flags, IPPROTO_TCP);
+    if (new_s == -1) {
+        return -1;
+    }
+
+    enable = 1;
+    if (setsockopt(new_s, SOL_SOCKET, SO_REUSEADDR, (char *) &enable, sizeof(enable)) ==
+        -1) {
+        close(new_s);
+        return -1;
+    }
+
+    memset(&addr, 0, sizeof(addr));
+    addr.sin_family = AF_INET;
+    /* If the modbus port is < to 1024, we need the setuid root. */
+    addr.sin_port = htons(ctx_tcp->port);
+    if (ctx_tcp->ip[0] == '0') {
+        /* Listen any addresses */
+        addr.sin_addr.s_addr = htonl(INADDR_ANY);
+    } else {
+        /* Listen only specified IP address */
+        rc = inet_pton(addr.sin_family, ctx_tcp->ip, &(addr.sin_addr));
+        if (rc <= 0) {
+            if (ctx->debug) {
+                fprintf(stderr, "Invalid IP address: %s\n", ctx_tcp->ip);
+            }
+            close(new_s);
+            return -1;
+        }
+    }
+
+    if (bind(new_s, (struct sockaddr *) &addr, sizeof(addr)) == -1) {
+        close(new_s);
+        return -1;
+    }
+
+    if (listen(new_s, nb_connection) == -1) {
+        close(new_s);
+        return -1;
+    }
+
+    return new_s;
+}
+
+int modbus_tcp_pi_listen(modbus_t *ctx, int nb_connection)
+{
+    int rc;
+    struct addrinfo *ai_list;
+    struct addrinfo *ai_ptr;
+    struct addrinfo ai_hints;
+    const char *node;
+    const char *service;
+    int new_s;
+    modbus_tcp_pi_t *ctx_tcp_pi;
+
+    if (ctx == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    ctx_tcp_pi = ctx->backend_data;
+
+#ifdef OS_WIN32
+    if (_modbus_tcp_init_win32() == -1) {
+        return -1;
+    }
+#endif
+
+    if (ctx_tcp_pi->node[0] == 0) {
+        node = NULL; /* == any */
+    } else {
+        node = ctx_tcp_pi->node;
+    }
+
+    if (ctx_tcp_pi->service[0] == 0) {
+        service = "502";
+    } else {
+        service = ctx_tcp_pi->service;
+    }
+
+    memset(&ai_hints, 0, sizeof(ai_hints));
+    /* If node is not NULL, than the AI_PASSIVE flag is ignored. */
+    ai_hints.ai_flags |= AI_PASSIVE;
+#ifdef AI_ADDRCONFIG
+    ai_hints.ai_flags |= AI_ADDRCONFIG;
+#endif
+    ai_hints.ai_family = AF_UNSPEC;
+    ai_hints.ai_socktype = SOCK_STREAM;
+    ai_hints.ai_addr = NULL;
+    ai_hints.ai_canonname = NULL;
+    ai_hints.ai_next = NULL;
+
+    ai_list = NULL;
+    rc = getaddrinfo(node, service, &ai_hints, &ai_list);
+    if (rc != 0) {
+        if (ctx->debug) {
+            fprintf(stderr, "Error returned by getaddrinfo: %s\n", gai_strerror(rc));
+        }
+        errno = ECONNREFUSED;
+        return -1;
+    }
+
+    new_s = -1;
+    for (ai_ptr = ai_list; ai_ptr != NULL; ai_ptr = ai_ptr->ai_next) {
+        int flags = ai_ptr->ai_socktype;
+        int s;
+
+#ifdef SOCK_CLOEXEC
+        flags |= SOCK_CLOEXEC;
+#endif
+
+        s = socket(ai_ptr->ai_family, flags, ai_ptr->ai_protocol);
+        if (s < 0) {
+            if (ctx->debug) {
+                perror("socket");
+            }
+            continue;
+        } else {
+            int enable = 1;
+            rc =
+                setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (void *) &enable, sizeof(enable));
+            if (rc != 0) {
+                close(s);
+                if (ctx->debug) {
+                    perror("setsockopt");
+                }
+                continue;
+            }
+        }
+
+        rc = bind(s, ai_ptr->ai_addr, ai_ptr->ai_addrlen);
+        if (rc != 0) {
+            close(s);
+            if (ctx->debug) {
+                perror("bind");
+            }
+            continue;
+        }
+
+        rc = listen(s, nb_connection);
+        if (rc != 0) {
+            close(s);
+            if (ctx->debug) {
+                perror("listen");
+            }
+            continue;
+        }
+
+        new_s = s;
+        break;
+    }
+    freeaddrinfo(ai_list);
+
+    if (new_s < 0) {
+        return -1;
+    }
+
+    return new_s;
+}
+
+int modbus_tcp_accept(modbus_t *ctx, int *s)
+{
+    struct sockaddr_in addr;
+    socklen_t addrlen;
+
+    if (ctx == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    addrlen = sizeof(addr);
+#ifdef HAVE_ACCEPT4
+    /* Inherit socket flags and use accept4 call */
+    ctx->s = accept4(*s, (struct sockaddr *) &addr, &addrlen, SOCK_CLOEXEC);
+#else
+    ctx->s = accept(*s, (struct sockaddr *) &addr, &addrlen);
+#endif
+
+    if (ctx->s < 0) {
+        return -1;
+    }
+
+    if (ctx->debug) {
+        char buf[INET_ADDRSTRLEN];
+        if (inet_ntop(AF_INET, &(addr.sin_addr), buf, INET_ADDRSTRLEN) == NULL) {
+            fprintf(stderr, "Client connection accepted from unparsable IP.\n");
+        } else {
+            printf("Client connection accepted from %s.\n", buf);
+        }
+    }
+
+    return ctx->s;
+}
+
+int modbus_tcp_pi_accept(modbus_t *ctx, int *s)
+{
+    struct sockaddr_in6 addr;
+    socklen_t addrlen;
+
+    if (ctx == NULL) {
+        errno = EINVAL;
+        return -1;
+    }
+
+    addrlen = sizeof(addr);
+#ifdef HAVE_ACCEPT4
+    /* Inherit socket flags and use accept4 call */
+    ctx->s = accept4(*s, (struct sockaddr *) &addr, &addrlen, SOCK_CLOEXEC);
+#else
+    ctx->s = accept(*s, (struct sockaddr *) &addr, &addrlen);
+#endif
+
+    if (ctx->s < 0) {
+        return -1;
+    }
+
+    if (ctx->debug) {
+        char buf[INET6_ADDRSTRLEN];
+        if (inet_ntop(AF_INET6, &(addr.sin6_addr), buf, INET6_ADDRSTRLEN) == NULL) {
+            fprintf(stderr, "Client connection accepted from unparsable IP.\n");
+        } else {
+            printf("Client connection accepted from %s.\n", buf);
+        }
+    }
+
+    return ctx->s;
+}
+
+static int
+_modbus_tcp_select(modbus_t *ctx, fd_set *rset, struct timeval *tv, int length_to_read)
+{
+    int s_rc;
+    while ((s_rc = select(ctx->s + 1, rset, NULL, NULL, tv)) == -1) {
+        if (errno == EINTR) {
+            if (ctx->debug) {
+                fprintf(stderr, "A non blocked signal was caught\n");
+            }
+            /* Necessary after an error */
+            FD_ZERO(rset);
+            FD_SET(ctx->s, rset);
+        } else {
+            return -1;
+        }
+    }
+
+    if (s_rc == 0) {
+        errno = ETIMEDOUT;
+        return -1;
+    }
+
+    return s_rc;
+}
+
+static void _modbus_tcp_free(modbus_t *ctx)
+{
+    if (ctx->backend_data) {
+        free(ctx->backend_data);
+    }
+    free(ctx);
+}
+
+static void _modbus_tcp_pi_free(modbus_t *ctx)
+{
+    if (ctx->backend_data) {
+        modbus_tcp_pi_t *ctx_tcp_pi = ctx->backend_data;
+        free(ctx_tcp_pi->node);
+        free(ctx_tcp_pi->service);
+        free(ctx->backend_data);
+    }
+
+    free(ctx);
+}
+
+// clang-format off
+const modbus_backend_t _modbus_tcp_backend = {
+    _MODBUS_BACKEND_TYPE_TCP,
+    _MODBUS_TCP_HEADER_LENGTH,
+    _MODBUS_TCP_CHECKSUM_LENGTH,
+    MODBUS_TCP_MAX_ADU_LENGTH,
+    _modbus_set_slave,
+    _modbus_tcp_build_request_basis,
+    _modbus_tcp_build_response_basis,
+    _modbus_tcp_prepare_response_tid,
+    _modbus_tcp_send_msg_pre,
+    _modbus_tcp_send,
+    _modbus_tcp_receive,
+    _modbus_tcp_recv,
+    _modbus_tcp_check_integrity,
+    _modbus_tcp_pre_check_confirmation,
+    _modbus_tcp_connect,
+    _modbus_tcp_is_connected,
+    _modbus_tcp_close,
+    _modbus_tcp_flush,
+    _modbus_tcp_select,
+    _modbus_tcp_free
+};
+
+const modbus_backend_t _modbus_tcp_pi_backend = {
+    _MODBUS_BACKEND_TYPE_TCP,
+    _MODBUS_TCP_HEADER_LENGTH,
+    _MODBUS_TCP_CHECKSUM_LENGTH,
+    MODBUS_TCP_MAX_ADU_LENGTH,
+    _modbus_set_slave,
+    _modbus_tcp_build_request_basis,
+    _modbus_tcp_build_response_basis,
+    _modbus_tcp_prepare_response_tid,
+    _modbus_tcp_send_msg_pre,
+    _modbus_tcp_send,
+    _modbus_tcp_receive,
+    _modbus_tcp_recv,
+    _modbus_tcp_check_integrity,
+    _modbus_tcp_pre_check_confirmation,
+    _modbus_tcp_pi_connect,
+    _modbus_tcp_is_connected,
+    _modbus_tcp_close,
+    _modbus_tcp_flush,
+    _modbus_tcp_select,
+    _modbus_tcp_pi_free
+};
+
+// clang-format on
+
+modbus_t *modbus_new_tcp(const char *ip, int port)
+{
+    modbus_t *ctx;
+    modbus_tcp_t *ctx_tcp;
+    size_t dest_size;
+    size_t ret_size;
+
+#if defined(OS_BSD)
+    /* MSG_NOSIGNAL is unsupported on *BSD so we install an ignore
+       handler for SIGPIPE. */
+    struct sigaction sa;
+
+    sa.sa_handler = SIG_IGN;
+    if (sigaction(SIGPIPE, &sa, NULL) < 0) {
+        /* The debug flag can't be set here... */
+        fprintf(stderr, "Could not install SIGPIPE handler.\n");
+        return NULL;
+    }
+#endif
+
+    ctx = (modbus_t *) malloc(sizeof(modbus_t));
+    if (ctx == NULL) {
+        return NULL;
+    }
+    _modbus_init_common(ctx);
+
+    /* Could be changed after to reach a remote serial Modbus device */
+    ctx->slave = MODBUS_TCP_SLAVE;
+
+    ctx->backend = &_modbus_tcp_backend;
+
+    ctx->backend_data = (modbus_tcp_t *) malloc(sizeof(modbus_tcp_t));
+    if (ctx->backend_data == NULL) {
+        modbus_free(ctx);
+        errno = ENOMEM;
+        return NULL;
+    }
+    ctx_tcp = (modbus_tcp_t *) ctx->backend_data;
+
+    if (ip != NULL) {
+        dest_size = sizeof(char) * 16;
+        ret_size = strlcpy(ctx_tcp->ip, ip, dest_size);
+        if (ret_size == 0) {
+            fprintf(stderr, "The IP string is empty\n");
+            modbus_free(ctx);
+            errno = EINVAL;
+            return NULL;
+        }
+
+        if (ret_size >= dest_size) {
+            fprintf(stderr, "The IP string has been truncated\n");
+            modbus_free(ctx);
+            errno = EINVAL;
+            return NULL;
+        }
+    } else {
+        ctx_tcp->ip[0] = '0';
+    }
+    ctx_tcp->port = port;
+    ctx_tcp->t_id = 0;
+
+    return ctx;
+}
+
+modbus_t *modbus_new_tcp_pi(const char *node, const char *service)
+{
+    modbus_t *ctx;
+    modbus_tcp_pi_t *ctx_tcp_pi;
+
+    ctx = (modbus_t *) malloc(sizeof(modbus_t));
+    if (ctx == NULL) {
+        return NULL;
+    }
+    _modbus_init_common(ctx);
+
+    /* Could be changed after to reach a remote serial Modbus device */
+    ctx->slave = MODBUS_TCP_SLAVE;
+
+    ctx->backend = &_modbus_tcp_pi_backend;
+
+    ctx->backend_data = (modbus_tcp_pi_t *) malloc(sizeof(modbus_tcp_pi_t));
+    if (ctx->backend_data == NULL) {
+        modbus_free(ctx);
+        errno = ENOMEM;
+        return NULL;
+    }
+    ctx_tcp_pi = (modbus_tcp_pi_t *) ctx->backend_data;
+    ctx_tcp_pi->node = NULL;
+    ctx_tcp_pi->service = NULL;
+
+    if (node != NULL) {
+        ctx_tcp_pi->node = strdup(node);
+    } else {
+        /* The node argument can be empty to indicate any hosts */
+        ctx_tcp_pi->node = strdup("");
+    }
+
+    if (ctx_tcp_pi->node == NULL) {
+        modbus_free(ctx);
+        errno = ENOMEM;
+        return NULL;
+    }
+
+    if (service != NULL && service[0] != '\0') {
+        ctx_tcp_pi->service = strdup(service);
+    } else {
+        /* Default Modbus port number */
+        ctx_tcp_pi->service = strdup("502");
+    }
+
+    if (ctx_tcp_pi->service == NULL) {
+        modbus_free(ctx);
+        errno = ENOMEM;
+        return NULL;
+    }
+
+    ctx_tcp_pi->t_id = 0;
+
+    return ctx;
+}

src/modbus-version.h.in

@@ -0,0 +1,51 @@
+/*
+ * Copyright © Stéphane Raimbault <stephane.raimbault@gmail.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef MODBUS_VERSION_H
+#define MODBUS_VERSION_H
+
+/* The major version, (1, if %LIBMODBUS_VERSION is 1.2.3) */
+#define LIBMODBUS_VERSION_MAJOR (@LIBMODBUS_VERSION_MAJOR@)
+
+/* The minor version (2, if %LIBMODBUS_VERSION is 1.2.3) */
+#define LIBMODBUS_VERSION_MINOR (@LIBMODBUS_VERSION_MINOR@)
+
+/* The micro version (3, if %LIBMODBUS_VERSION is 1.2.3) */
+#define LIBMODBUS_VERSION_MICRO (@LIBMODBUS_VERSION_MICRO@)
+
+/* The full version, like 1.2.3 */
+#define LIBMODBUS_VERSION @LIBMODBUS_VERSION@
+
+/* The full version, in string form (suited for string concatenation)
+ */
+#define LIBMODBUS_VERSION_STRING "@LIBMODBUS_VERSION@"
+
+/* Numerically encoded version, eg. v1.2.3 is 0x010203 */
+#define LIBMODBUS_VERSION_HEX                                                                      \
+    ((LIBMODBUS_VERSION_MAJOR << 16) | (LIBMODBUS_VERSION_MINOR << 8) |                            \
+     (LIBMODBUS_VERSION_MICRO << 0))
+
+/* Evaluates to True if the version is greater than @major, @minor and @micro
+ */
+#define LIBMODBUS_VERSION_CHECK(major, minor, micro)                                               \
+    (LIBMODBUS_VERSION_MAJOR > (major) ||                                                          \
+     (LIBMODBUS_VERSION_MAJOR == (major) && LIBMODBUS_VERSION_MINOR > (minor)) ||                  \
+     (LIBMODBUS_VERSION_MAJOR == (major) && LIBMODBUS_VERSION_MINOR == (minor) &&                  \
+      LIBMODBUS_VERSION_MICRO >= (micro)))
+
+#endif /* MODBUS_VERSION_H */