Python serial to tcp

s2net.py

"""
tsb.py -- A telnet <-> serial port bridge
Copyright (C) 2005 Eli Fulkerson

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program 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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

----------------------------------------------------------------------

Other license terms may be negotiable.  Contact the author if you would
like copy that is licensed differently.

Additionally, this script requires the use of "pyserial", which is licensed
separately by its author.  This library can be found at http://pyserial.sourceforge.net/

Contact information (as well as this script) lives at http://www.elifulkerson.com

Original version available at:
https://www.elifulkerson.com/projects/telnet-serial-bridge.php

Usage: tsb [OPTIONS]
Creates a TCP<->Serial port bridge, which allows a telnet client to
cross over a Serial port.

Serial Options:
   -p, --port     :  Specify the desired serial port.
                     (0 for COM1, 1 for COM2 etc)
   -r, --baudrate :  Specify baudrate
   -s, --bytesize :  Specify bytesize
   -y, --parity   :  Specify parity options
   -b, --stopbits :  Specify number of stopbits
   -t, --timeout  :  Specify timeout
   -f, --flow     :  Specify flow-control options

TCP Options:
   -l, --listen   :  Specify a TCP port to listen on

General Options:
   -h, --help     :  Display this help messsage
"""

# standard libraries
from socket import *
from select import *
from string import *
import sys
from getopt import getopt, GetoptError

# nonstandard library
import serial

"""
print usage, then exit
"""
def usage():
    usagestring = """Usage: tsb [OPTIONS]
Creates a TCP<->Serial port bridge, which allows a telnet client to
cross over a Serial port.

Serial Options:
   -p, --port     :  Specify the desired serial port.
                     (0 for COM1, 1 for COM2 etc)
   -r, --baudrate :  Specify baudrate
   -s, --bytesize :  Specify bytesize
   -y, --parity   :  Specify parity options
   -b, --stopbits :  Specify number of stopbits
   -t, --timeout  :  Specify timeout
   -f, --flow     :  Specify flow-control options
   
TCP Options:
   -l, --listen   :  Specify a TCP port to listen on

General Options:
   -h, --help     :  Display this help messsage

"""
    print usagestring
    sys.exit(0)



"""
Function cleans up telnet's output for input into the serial port.
Telnet is fancier than serial, so we have to strip some things out.
"""
def cleanup_for_serial(text):
    """
    chr(255) is the "we are negotiating" leading bit.  If it is the first bit in
    a packet, we do not want to send it on to the serial port
    """
    if ord(text[:1]) == 255:
        return ""

    """
    For some reason, windows likes to send "cr/lf" when you send a "cr".
    Strip that so we don't get a double prompt.\
    """
    text = replace(text, chr(13) + chr(10), chr(13))

    
    return text


class Connection:
    "A connection is a class that forwards requests between TCP and Serial"
    def __init__(self, socket, com):
        self.socket = socket
        self.com = com

    def fileno(self):
        "Required, look it up"
        return self.socket.fileno()

    def init_tcp(self):
        "Set up the TCP connection and do telnet negotiation"

        "telnet negotiation:  we don't want linemode"
        "      COMMAND,   DONT,      linemode"
        data = chr(255) + chr(254) + chr(34)
        self.socket.send(data)

        "telnet negotation:  we don't want local echo"
        "      COMMAND,   DONT,      echo"
        data = chr(255) + chr(254) + chr(1)
        self.socket.send(data)

        "send the header"
        self.socket.send("************************************************\r\n")
        self.socket.send("Telnet <--> Serial Bridge by Eli Fulkerson\r\n")
        self.socket.send("http://www.elifulkerson.com for updates       \r\n")
        self.socket.send("\r\n")
        self.socket.send("This program uses non-standard python libraries:\r\n")
        self.socket.send("   - pyserial by Chris Liechti\r\n")
        self.socket.send("   - pywin32 by Mark Hammond (et al)\r\n")
        self.socket.send("\r\n")
        self.socket.send("************************************************\r\n")

        self.socket.send("\r\n")
        self.socket.send("You are now connected to %s.\r\n" % self.com.portstr)
        


    def recv_tcp(self):
        "Receive some data from the telnet client"
        data =  self.socket.recv(1024)
        return data

    def send_tcp(self, data):
        "Send some data out to the telnet client"
        self.socket.send(data)

    def recv_serial(self):
        "Recieve some data from the serial port"
        data = self.com.read(self.com.inWaiting() )
        return data

    def send_serial(self,data):
        "Send some data out to the serial port"
        data = cleanup_for_serial(data)

        try:
            if ord(data) == 3:
                self.com.sendbreak()
		return
        except:
            pass


        self.com.write(data)

    

class Handler:
    def __init__(self):
        global LISTEN
        global com
        
        self.clist = [ ]
        self.tcpconnected = False
        self.serialconnected = False

        self.start_new_listener()
        
        print "TCP to Serial bridge is up: telnet to localhost:%s to access %s." % (LISTEN, com.portstr)
        print "(Control-C to exit)"

    def start_new_listener(self):
        self.listener = socket(AF_INET, SOCK_STREAM)
        self.listener.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
        self.listener.bind(('', LISTEN))
        self.listener.listen(32)

    def run(self):
        """
        yes, this was originally going to be multi-user, I don't feel like changing it
        now though.  We shall loop.
        """
        for conn in self.clist[:]:
            if conn.com.isOpen():
                "pull data from serial and send it to tcp if possible"
                data = conn.recv_serial()
                if not data:
                    pass
                else:
                    conn.send_tcp(data)

        ready = self.clist[:]

        if self.listener:
            ready.append(self.listener)
            
        ready = select(ready, [], [], 0.1)[0]
        for conn in ready:
            if conn is self.listener:
                socket, address = self.listener.accept()


                global com

                try:
                    com.close()
                    com.open()
                except serial.SerialException:
                    print "Error opening serial port.  Is it in use?"
                    sys.exit(1)
                
                
                conn = Connection(socket, com)
                self.clist.append(conn)

                "set up our initial telnet environment"
                conn.init_tcp()

                "we don't need to listen anymore"
                self.listener = None

            else:
                "pull some data from tcp and send it to serial, if possible."
                data = conn.recv_tcp()
                if not data:
                    print "TCP connection closed."
                    self.clist.remove(conn)
                    self.start_new_listener()

                    
                else:
                    conn.send_serial(data)

        
def main(argv=None):

    "Pull in our arguments if we were not spoonfed some"
    if argv is None:
        argv = sys.argv

    "Parse our arguments"
    try:
        options, args = getopt(argv[1:], "p:r:s:y:b:t:f:l:h", ["port=", "baudrate=", "bytesize=", "parity=", "stopbits=", "timeout=", "flow=", "listen=", "help"])
    except GetoptError:
        usage()
        return    

    global LISTEN  # int, the TCP port to listen on
    global com     # the serial connection itself


    "first, loop through and open the right port"
    got_a_serial_port = False
    for o,a in options:
        if o in ("-p", "--port"):
            a = int(a)
            try:
                com = serial.Serial(a)
                #print "Serial port opened: %s" % (com.portstr)
                got_a_serial_port = True
            except:
                print "Couldn't open serial port: %s" % (a)
                print "This should be a numerical value.  0 == COM1, 1 == COM2, etc"
                sys.exit(1)
        if o in ("-h", "--help"):
            usage()
            return

    if not got_a_serial_port:
        # we don't have a port.  Fine, use the default.
        try:
            com = serial.Serial(0)
            #print "Serial port opened: %s" % (com.portstr)
        except:
            print "Couldn't open serial port: %s" % (0)
            sys.exit(1)


    # sensible defaults
    com.baudrate = 9600
    com.timeout = 0
    com.bytesize = serial.EIGHTBITS
    com.parity = serial.PARITY_NONE
    com.stopbits = serial.STOPBITS_ONE
    com.xonxoff = 0
    com.rtscts = 0
    LISTEN = 23      

    # now loop through the other options   
    for o,a in options:
        
        if o in ("-l", "--listen"):
            a = int(a)
            if a < 1 or a > 65535:
                print "Invalid listening (tcp) port.  Valid ports are 1-65535"
                sys.exit(1)
            else:
                LISTEN = a
            
        if o in ("-r", "--baudrate"):
            a = int(a)
            if a in com.BAUDRATES:
                #print "Setting baudrate to %s." % (a)
                com.baudrate = a
            else:
                print "Valid baudrates are:", com.BAUDRATES
                sys.exit(1)

        if o in ("-s", "--bytesize"):
            a = int(a)
            if a in com.BYTESIZES:
                #print "Setting bytesize to %s." % (a)
                com.bytesize = a
            else:
                print "Valid bytesizes are:", com.BYTESIZES
                sys.exit(1)

        if o in ("-y", "--parity"):
            if a in com.PARITIES:
                #print "Setting parity to %s." % (a)
                com.parity = a
            else:
                print "Valid parities are:", com.PARITIES
                sys.exit(1)

        if o in ("-b", "--stopbits"):
            a = float(a)
            if a in com.STOPBITS:
                #print "Setting stopbits to %s." % (a)
                com.stopbits = a
            else:
                print "Valid stopbits are:", com.STOPBITS
                sys.exit(1)

        if o in ("-t", "--timeout"):
            a = int(a)
            if a < 0 or a > 100:
                print "Valid timesouts are 0-100."
                sys.exit(1)
            else:
                com.timeout = a

        if o in ("-f", "--flow"):
            FLOWS = ("xonxoff", "rtscts", "none")
            if a in FLOWS:
                #print "Setting flow control to %s" % (a)

                if a == "xonxoff":
                    com.xonxoff = True
                if a == "rtscts":
                    com.rtscts = True
            else:
                print "Valid flow-controls are:", FLOWS
                sys.exit(1)
    # print out com's statistics
    print "------------------------"
    print "Serial Port Information:"
    print "------------------------"
    print "port:     %s" % com.portstr
    print "baudrate: %s" % com.baudrate
    print "bytesize: %s" % com.bytesize
    print "parity:   %s" % com.parity
    print "stopbits: %s" % com.stopbits
    print "timeout:  %s" % com.timeout
    print "xonxoff:  %s" % com.xonxoff
    print "rtscts:   %s" % com.rtscts
    print ""
    print "------------------------"
    print "TCP/IP Port Information:"
    print "------------------------"
    print "host:     %s" % "localhost"
    print "port:     %s" % LISTEN
    print ""


    # start up our run loop    
    connections = Handler()
    while 1:
        connections.run()


if __name__== "__main__":
    try:
        main()
    except KeyboardInterrupt:
        print "Keyboard Interrupt"

I also recommend having a look at the pyserial project.

The documentation provides examples on how to build:

• TCP to serial bridge
• RFC2217 single port TCP bridge
• RFC2217 multi port TCP bridge

I also develop a library called serialio which comes with a ready to use TCP bridge.
It is far less tested than the well known pyserial but if you want to have a try I would welcome the feedback :-)

@marios-stam

What I wanted was quite straight forward so I used pyserial. I used this code:

import serial
import serial.tools.list_ports as port_list
import socket

host = '127.0.0.1'
port = 23200
port1 = 23300
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

ports = list(port_list.comports())
for p in ports:
print (p)

ser = serial.Serial('com6', baudrate=9600)
print (ser.name)

while True:
data=(ser.readline())
print (data)
s.sendto(data, (host, port))
s.sendto(data, (host, port1))
ser.close()

I needed UDP but if you need TCP just change de socket definition.