libmodbus-sys 0.8.0

FFI bindings to the libmodbus C library.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141

/*
 * 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 <signal.h>

#include <modbus.h>

#if defined(_WIN32)
#include <ws2tcpip.h>
#else
#include <sys/select.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#endif

#define NB_CONNECTION    5

static modbus_t *ctx = NULL;
static modbus_mapping_t *mb_mapping;

static int server_socket = -1;

static void close_sigint(int dummy)
{
    if (server_socket != -1) {
        close(server_socket);
    }
    modbus_free(ctx);
    modbus_mapping_free(mb_mapping);

    exit(dummy);
}

int main(void)
{
    uint8_t query[MODBUS_TCP_MAX_ADU_LENGTH];
    int master_socket;
    int rc;
    fd_set refset;
    fd_set rdset;
    /* Maximum file descriptor number */
    int fdmax;

    ctx = modbus_new_tcp("127.0.0.1", 1502);

    mb_mapping = modbus_mapping_new(MODBUS_MAX_READ_BITS, 0,
                                    MODBUS_MAX_READ_REGISTERS, 0);
    if (mb_mapping == NULL) {
        fprintf(stderr, "Failed to allocate the mapping: %s\n",
                modbus_strerror(errno));
        modbus_free(ctx);
        return -1;
    }

    server_socket = modbus_tcp_listen(ctx, NB_CONNECTION);
    if (server_socket == -1) {
        fprintf(stderr, "Unable to listen TCP connection\n");
        modbus_free(ctx);
        return -1;
    }

    signal(SIGINT, close_sigint);

    /* Clear the reference set of socket */
    FD_ZERO(&refset);
    /* Add the server socket */
    FD_SET(server_socket, &refset);

    /* Keep track of the max file descriptor */
    fdmax = server_socket;

    for (;;) {
        rdset = refset;
        if (select(fdmax+1, &rdset, NULL, NULL, NULL) == -1) {
            perror("Server select() failure.");
            close_sigint(1);
        }

        /* Run through the existing connections looking for data to be
         * read */
        for (master_socket = 0; master_socket <= fdmax; master_socket++) {

            if (!FD_ISSET(master_socket, &rdset)) {
                continue;
            }

            if (master_socket == server_socket) {
                /* A client is asking a new connection */
                socklen_t addrlen;
                struct sockaddr_in clientaddr;
                int newfd;

                /* Handle new connections */
                addrlen = sizeof(clientaddr);
                memset(&clientaddr, 0, sizeof(clientaddr));
                newfd = accept(server_socket, (struct sockaddr *)&clientaddr, &addrlen);
                if (newfd == -1) {
                    perror("Server accept() error");
                } else {
                    FD_SET(newfd, &refset);

                    if (newfd > fdmax) {
                        /* Keep track of the maximum */
                        fdmax = newfd;
                    }
                    printf("New connection from %s:%d on socket %d\n",
                           inet_ntoa(clientaddr.sin_addr), clientaddr.sin_port, newfd);
                }
            } else {
                modbus_set_socket(ctx, master_socket);
                rc = modbus_receive(ctx, query);
                if (rc > 0) {
                    modbus_reply(ctx, query, rc, mb_mapping);
                } else if (rc == -1) {
                    /* This example server in ended on connection closing or
                     * any errors. */
                    printf("Connection closed on socket %d\n", master_socket);
                    close(master_socket);

                    /* Remove from reference set */
                    FD_CLR(master_socket, &refset);

                    if (master_socket == fdmax) {
                        fdmax--;
                    }
                }
            }
        }
    }

    return 0;
}