mqtt-sn-serial-bridge.c

/*
  MQTT-SN serial bridge
  Copyright (C) 2014-2016 Nicholas Humfrey

  Permission is hereby granted, free of charge, to any person obtaining
  a copy of this software and associated documentation files (the
  "Software"), to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify, merge, publish,
  distribute, sublicense, and/or sell copies of the Software, and to
  permit persons to whom the Software is furnished to do so, subject to
  the following conditions:

  The above copyright notice and this permission notice shall be
  included in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

//#define _POSIX_SOURCE 1 /* POSIX compliant source */

#include <stdio.h>
#include <unistd.h>
#include <getopt.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <netdb.h>
#include <fcntl.h>
#include <termios.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <signal.h>
#include <errno.h>

#include "mqtt-sn.h"


const char *mqtt_sn_host = "127.0.0.1";
const char *mqtt_sn_port = MQTT_SN_DEFAULT_PORT;
const char *serial_device = NULL;
speed_t serial_baud = B9600;
uint8_t debug = 0;
uint8_t frwdencap = FALSE;

uint8_t keep_running = TRUE;


static void usage()
{
    fprintf(stderr, "Usage: mqtt-sn-serial-bridge [opts] <device>\n");
    fprintf(stderr, "\n");
    fprintf(stderr, "  -b <baud>      Set the baud rate. Defaults to %d.\n", (int)serial_baud);
    fprintf(stderr, "  -d             Increase debug level by one. -d can occur multiple times.\n");
    fprintf(stderr, "  -dd            Enable extended debugging - display packets in hex.\n");
    fprintf(stderr, "  -h <host>      MQTT-SN host to connect to. Defaults to '%s'.\n", mqtt_sn_host);
    fprintf(stderr, "  -p <port>      Network port to connect to. Defaults to %s.\n", mqtt_sn_port);
    fprintf(stderr, "  --fe           Enables Forwarder Encapsulation. Mqtt-sn packets are encapsulated according to MQTT-SN Protocol Specification v1.2, chapter 5.5 Forwarder Encapsulation.\n");
    exit(EXIT_FAILURE);
}

static void parse_opts(int argc, char** argv)
{

    static struct option long_options[] =
    {
        {"fe",    no_argument,       0, 1000 },
        {0, 0, 0, 0}
    };

    int ch;
    /* getopt_long stores the option index here. */
    int option_index = 0;

    // Parse the options/switches
    while ((ch = getopt_long (argc, argv, "b:dh:p:?", long_options, &option_index)) != -1)
    {
        switch (ch) {
        case 'b':
            serial_baud = atoi(optarg);
            break;

        case 'd':
            debug++;
            break;

        case 'h':
            mqtt_sn_host = optarg;
            break;

        case 'p':
            mqtt_sn_port = optarg;
            break;

        case 1000:
            mqtt_sn_enable_frwdencap();
            frwdencap = TRUE;
            break;
        case '?':
        default:
            usage();
            break;
        } // switch
    } // while

    // Final argument is the serial port device path
    if (argc-optind < 1) {
        fprintf(stderr, "Missing serial port.\n");
        usage();
    } else {
        serial_device = argv[optind];
    }
}


static int serial_open(const char* device_path)
{
    struct termios tios;
    int fd;

    mqtt_sn_disable_frwdencap();

    mqtt_sn_log_debug("Opening %s", device_path);

    fd = open(device_path, O_RDWR | O_NOCTTY | O_NDELAY);
    if (fd < 0) {
        perror(device_path);
        exit(EXIT_FAILURE);
    }

    // Turn back on blocking reads
    fcntl(fd, F_SETFL, 0);

    // Read existing serial port settings
    tcgetattr(fd, &tios);

    // Set the input and output baud rates
    cfsetispeed(&tios, serial_baud);
    cfsetospeed(&tios, serial_baud);

    // Set to local mode
    tios.c_cflag |= CLOCAL | CREAD;

    // Set serial port mode to 8N1
    tios.c_cflag &= ~PARENB;
    tios.c_cflag &= ~CSTOPB;
    tios.c_cflag &= ~CSIZE;
    tios.c_cflag |= CS8;

    // Turn off flow control and ignore parity
    tios.c_iflag &= ~(IXON | IXOFF | IXANY);
    tios.c_iflag |= IGNPAR;

    // Turn off output post-processing
    tios.c_oflag &= ~OPOST;

    // set input mode (non-canonical, no echo,...)
    tios.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);

    // Set VMIN high, so that we wait for a gap in the data
    // http://www.unixwiz.net/techtips/termios-vmin-vtime.html
    tios.c_cc[VMIN]     = 255;
    tios.c_cc[VTIME]    = 1;

    tcsetattr(fd, TCSAFLUSH, &tios);

    // Flush the input buffer
    sleep(1);
    tcflush(fd, TCIOFLUSH);

    return fd;
}

static void* serial_read_packet(int fd)
{
    static uint8_t buf[MQTT_SN_MAX_PACKET_LENGTH+1];

    // First get the length of the packet
    int bytes_read = read(fd, buf, 1);
    if (bytes_read != 1) {
        mqtt_sn_log_err("Error reading packet length from serial port: %d, %d", bytes_read, errno);
        return NULL;
    }

    if (buf[0] == 0x00) {
        mqtt_sn_log_err("Packets of length 0 are invalid.");
        return NULL;
    }

    // Read in the rest of the packet
    bytes_read = read(fd, &buf[1], buf[0]-1);
    if (bytes_read <= 0) {
        mqtt_sn_log_err("Error reading rest of packet from serial port: %d, %d", bytes_read, errno);
        return NULL;
    } else {
        bytes_read += 1;
    }

    if (mqtt_sn_validate_packet(buf, bytes_read) == FALSE) {
        return NULL;
    }

    // NULL-terminate the packet
    buf[bytes_read] = '\0';

    if (debug) {
        const char* type = mqtt_sn_type_string(buf[1]);
        mqtt_sn_log_debug("Serial -> UDP (bytes_read=%d, type=%s)", bytes_read, type);
        if (debug > 1) {
            int i;
            fprintf(stderr, "  ");
            for (i=0; i<buf[0]; i++) {
                fprintf(stderr, "0x%2.2X ", buf[i]);
            }
            fprintf(stderr, "\n");
        }
    }

    return buf;
}

void serial_write_packet(int fd, const void* packet)
{
    size_t sent, len = ((uint8_t*)packet)[0];

    sent = write(fd, packet, len);
    if (sent != len) {
        mqtt_sn_log_warn("Warning: only sent %d of %d bytes", (int)sent, (int)len);
    }
}

static void termination_handler (int signum)
{
    switch(signum) {
    case SIGHUP:
        mqtt_sn_log_debug("Got hangup signal.");
        break;
    case SIGTERM:
        mqtt_sn_log_debug("Got termination signal.");
        break;
    case SIGINT:
        mqtt_sn_log_debug("Got interrupt signal.");
        break;
    }

    // Signal the main thead to stop
    keep_running = FALSE;
}


int main(int argc, char* argv[])
{
    int fd = -1;
    int sock = -1;

    // Parse the command-line options
    parse_opts(argc, argv);

    mqtt_sn_set_debug(debug);

    // Setup signal handlers
    signal(SIGTERM, termination_handler);
    signal(SIGINT, termination_handler);
    signal(SIGHUP, termination_handler);

    // Create a UDP socket
    sock = mqtt_sn_create_socket(mqtt_sn_host, mqtt_sn_port);

    // Open the serial port
    fd = serial_open(serial_device);

    while (keep_running) {
        fd_set fdset;

        FD_ZERO(&fdset);                // Clear the socket set
        FD_SET(fd, &fdset);             // Add serial into fdset
        FD_SET(sock, &fdset);           // Add socket into fdset

        if (select(FD_SETSIZE, &fdset, NULL, NULL, NULL) < 0) {
            if (errno != EINTR) {
                perror("select");
            }
            break;
        }

        // Read serial line
        if (FD_ISSET(fd, &fdset)) {
            void *packet = serial_read_packet(fd);
            if (packet) {
                if (frwdencap) {
                    mqtt_sn_send_frwdencap_packet(sock, packet, NULL, 0);
                } else {
                    mqtt_sn_send_packet(sock, packet);
                }
            }
        }

        if (FD_ISSET(sock, &fdset)) {
            void *packet = mqtt_sn_receive_packet(sock);
            if (packet) {
                serial_write_packet(fd, packet);
            }
        }
    }

    close(sock);
    close(fd);

    mqtt_sn_cleanup();

    return 0;
}