1#!/usr/bin/env python
2#
3# redirect data from a TCP/IP connection to a serial port and vice versa
4# using RFC 2217
5#
6# (C) 2009-2015 Chris Liechti <[email protected]>
7#
8# SPDX-License-Identifier:    BSD-3-Clause
9
10import logging
11import socket
12import sys
13import time
14import threading
15import serial
16import serial.rfc2217
17
18
19class Redirector(object):
20    def __init__(self, serial_instance, socket, debug=False):
21        self.serial = serial_instance
22        self.socket = socket
23        self._write_lock = threading.Lock()
24        self.rfc2217 = serial.rfc2217.PortManager(
25            self.serial,
26            self,
27            logger=logging.getLogger('rfc2217.server') if debug else None)
28        self.log = logging.getLogger('redirector')
29
30    def statusline_poller(self):
31        self.log.debug('status line poll thread started')
32        while self.alive:
33            time.sleep(1)
34            self.rfc2217.check_modem_lines()
35        self.log.debug('status line poll thread terminated')
36
37    def shortcircuit(self):
38        """connect the serial port to the TCP port by copying everything
39           from one side to the other"""
40        self.alive = True
41        self.thread_read = threading.Thread(target=self.reader)
42        self.thread_read.daemon = True
43        self.thread_read.name = 'serial->socket'
44        self.thread_read.start()
45        self.thread_poll = threading.Thread(target=self.statusline_poller)
46        self.thread_poll.daemon = True
47        self.thread_poll.name = 'status line poll'
48        self.thread_poll.start()
49        self.writer()
50
51    def reader(self):
52        """loop forever and copy serial->socket"""
53        self.log.debug('reader thread started')
54        while self.alive:
55            try:
56                data = self.serial.read(self.serial.in_waiting or 1)
57                if data:
58                    # escape outgoing data when needed (Telnet IAC (0xff) character)
59                    self.write(b''.join(self.rfc2217.escape(data)))
60            except socket.error as msg:
61                self.log.error('{}'.format(msg))
62                # probably got disconnected
63                break
64        self.alive = False
65        self.log.debug('reader thread terminated')
66
67    def write(self, data):
68        """thread safe socket write with no data escaping. used to send telnet stuff"""
69        with self._write_lock:
70            self.socket.sendall(data)
71
72    def writer(self):
73        """loop forever and copy socket->serial"""
74        while self.alive:
75            try:
76                data = self.socket.recv(1024)
77                if not data:
78                    break
79                self.serial.write(b''.join(self.rfc2217.filter(data)))
80            except socket.error as msg:
81                self.log.error('{}'.format(msg))
82                # probably got disconnected
83                break
84        self.stop()
85
86    def stop(self):
87        """Stop copying"""
88        self.log.debug('stopping')
89        if self.alive:
90            self.alive = False
91            self.thread_read.join()
92            self.thread_poll.join()
93
94
95if __name__ == '__main__':
96    import argparse
97
98    parser = argparse.ArgumentParser(
99        description="RFC 2217 Serial to Network (TCP/IP) redirector.",
100        epilog="""\
101NOTE: no security measures are implemented. Anyone can remotely connect
102to this service over the network.
103
104Only one connection at once is supported. When the connection is terminated
105it waits for the next connect.
106""")
107
108    parser.add_argument('SERIALPORT')
109
110    parser.add_argument(
111        '-p', '--localport',
112        type=int,
113        help='local TCP port, default: %(default)s',
114        metavar='TCPPORT',
115        default=2217)
116
117    parser.add_argument(
118        '-v', '--verbose',
119        dest='verbosity',
120        action='count',
121        help='print more diagnostic messages (option can be given multiple times)',
122        default=0)
123
124    args = parser.parse_args()
125
126    if args.verbosity > 3:
127        args.verbosity = 3
128    level = (logging.WARNING,
129             logging.INFO,
130             logging.DEBUG,
131             logging.NOTSET)[args.verbosity]
132    logging.basicConfig(level=logging.INFO)
133    #~ logging.getLogger('root').setLevel(logging.INFO)
134    logging.getLogger('rfc2217').setLevel(level)
135
136    # connect to serial port
137    ser = serial.serial_for_url(args.SERIALPORT, do_not_open=True)
138    ser.timeout = 3     # required so that the reader thread can exit
139    # reset control line as no _remote_ "terminal" has been connected yet
140    ser.dtr = False
141    ser.rts = False
142
143    logging.info("RFC 2217 TCP/IP to Serial redirector - type Ctrl-C / BREAK to quit")
144
145    try:
146        ser.open()
147    except serial.SerialException as e:
148        logging.error("Could not open serial port {}: {}".format(ser.name, e))
149        sys.exit(1)
150
151    logging.info("Serving serial port: {}".format(ser.name))
152    settings = ser.get_settings()
153
154    srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
155    srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
156    srv.bind(('', args.localport))
157    srv.listen(1)
158    logging.info("TCP/IP port: {}".format(args.localport))
159    while True:
160        try:
161            client_socket, addr = srv.accept()
162            logging.info('Connected by {}:{}'.format(addr[0], addr[1]))
163            client_socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
164            ser.rts = True
165            ser.dtr = True
166            # enter network <-> serial loop
167            r = Redirector(
168                ser,
169                client_socket,
170                args.verbosity > 0)
171            try:
172                r.shortcircuit()
173            finally:
174                logging.info('Disconnected')
175                r.stop()
176                client_socket.close()
177                ser.dtr = False
178                ser.rts = False
179                # Restore port settings (may have been changed by RFC 2217
180                # capable client)
181                ser.apply_settings(settings)
182        except KeyboardInterrupt:
183            sys.stdout.write('\n')
184            break
185        except socket.error as msg:
186            logging.error(str(msg))
187
188    logging.info('--- exit ---')
189