In this example script, the modbus connection works properly when I call the service the first time, but it is closed unexpectedly when I call the service the second time, raising the following error:
Error processing request: Modbus Error: [Connection]
ModbusTcpClient({ip}): Connection unexpectedly closed 0.000089 seconds
into read of 8 bytes without response from unit before it closed
connection
#!/usr/bin/env python3
import rospy from pymodbus.client.sync
import ModbusTcpClient
from std_srvs.srv import Empty
driver = ModbusTcpClient("ip", port)
def srv_cb(req):
status = driver.read_holding_registers(0, 4).registers
print(status)
def close():
driver.close()
if __name__ == '__main__':
node_name = 'node'
rospy.init_node(node_name)
serv = rospy.Service('srv', Empty, srv_cb)
rospy.on_shutdown(close)
rospy.spin()
Could someone help me to understand what is happening?
Related
I'm using psycopg2 ThreadedConnectionPool.
When putting an already closed connection back in the pool using psycopg2's putconn, it doesn't get added to the pool, assuring that I won't be getting a closed connection next time I call get_conn.
Is there a case in which the connection is broken (as in not usable anymore) but not closed?
If so, how can I detect it?
For example:
from psycopg2.pool import ThreadedConnectionPool
DSN = "postgresql://User:password#localhost/db"
pool = ThreadedConnectionPool(8, 10, DSN)
def execute(query):
close = False
conn = pool.getconn()
try:
cur = conn.cursor()
cur.execute(query)
cur.commit()
except ExceptionThatIndicatesTheConnectionIsBrokenButNotClosed:
close = True
except Exception:
conn.rollback()
pool.putconn(conn, close=close)
ExceptionThatIndicatesTheConnectionIsBrokenButNotClosed - are there any specific exceptions/pgcodes/pgerros that indicate just that?
Thanks :)
This question already has answers here:
Execute multiple dependent commands individually with Paramiko and find out when each command finishes
(1 answer)
Executing command using "su -l" in SSH using Python
(1 answer)
Closed 5 days ago.
I wanted to wait the given command execution has been completed on remote machines. this case it just executed and return and not waiting till its completed.
import paramiko
import re
import time
def scp_switch(host, username, PasswdValue):
ssh = paramiko.SSHClient()
try:
# Logging into remote host as my credentials
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(host, username=username, password=PasswdValue ,timeout=30)
try:
# switcing to powerbroker/root mode
command = "pbrun xyz -u root\n"
channel = ssh.invoke_shell()
channel.send(command)
time.sleep(3)
while not re.search('Password',str(channel.recv(9999), 'utf-8')):
time.sleep(1)
print('Waiting...')
channel.send("%s\n" % PasswdValue)
time.sleep(3)
#Executing the command on remote host with root (post logged as root)
# I dont have any specific keyword to search in given output hence I am not using while loop here.
cmd = "/tmp/slp.sh cool >/tmp/slp_log.txt \n"
print('Executing %s' %cmd)
channel.send(cmd) # its not waiting here till the process completed,
time.sleep(3)
res = str(channel.recv(1024), 'utf-8')
print(res)
print('process completed')
except Exception as e:
print('Error while switching:', str(e))
except Exception as e:
print('Error while SSH : %s' % (str(e)))
ssh.close()
""" Provide the host and credentials here """
HOST = 'abcd.us.domain.com'
username = 'heyboy'
password = 'passcode'
scp_switch(HOST, username, password)
As per my research, it will not return any status code, is there any logic to get the return code and wait till the process completed?
I know this is an old post, but leaving this here in case someone has the same problem.
You can use an echo that will run in case your command executes successfully, for example if you are doing an scp ... && echo 'transfer complete', then you can catch this output with a loop
while True:
s = chan.recv(4096)
s = s.decode()
if 'transfer done' in s:
break
time.sleep(1)
I am setting up a new TCP Server connected to client through an Ethernet TCP/IP modbus and is supposed to push certain values to a given modbus register (hr = 6022), every few seconds. I do not see any exceptions/errors raised by the script but no data is received by the client. With a StartTCPserver command, I expected to see any network traffic (atleast the handshake) but I do not see any traffic on Wireshark. What could be the next possible diagnostic?
I have tried running similar script locally (without an external ethernet connection); One acting as a client and another as a server and did see the values update on the client register.
from pymodbus.server.sync import StartTcpServer
from pymodbus.device import ModbusDeviceIdentification
from pymodbus.datastore import ModbusSequentialDataBlock
from pymodbus.datastore import ModbusSlaveContext, ModbusServerContext
import time
import logging
FORMAT = ('%(asctime)-15s %(threadName)-15s'
' %(levelname)-8s %(module)-15s:%(lineno)-8s %(message)s')
logging.basicConfig(format=FORMAT)
log = logging.getLogger()
log.setLevel(logging.DEBUG)
def run_server():
store = ModbusSlaveContext(
ir=ModbusSequentialDataBlock(6022, [152, 276]),
zero_mode=True
)
context = ModbusServerContext(slaves=store, single=True)
StartTcpServer(context, address=("192.168.10.2", 502))
if __name__ == "__main__":
run_server()
The lines after run_server() are never reached. Code connecting to the server can be placed in a different script;
from pymodbus.client.sync import ModbusTcpClient as ModbusClient
cli = ModbusClient('192.168.10.2', port=502)
assert cli.connect()
res = cli.read_input_registers(6022, count=1, unit=1)
print(res.registers[0])
I'm working on a serial port using pymodbus3.
When I run the following code the output is 'None'. Whereas I can get response from the device when test for the serial port with modpoll.
How can I fix this issue?
from pymodbus3.client.sync import ModbusSerialClient as mbc
def PortTest(self):
client = mbc(method="rtu", port="/dev/ttyUSB0", stopbits=1, bytesize=8, parity='N', baudrate=9600)
try:
client.connect()
coil = client.read_coils(0, 1)
print(coil)
client.close()
except OSError as err:
raise EnvironmentError(err)
pass
pymodbus3 has a bug. Uninstall it and replace it with the python 3 branch of pymodbus 1.2.0. Go to github and download it.
https://github.com/bashwork/pymodbus/tree/python3
This question is two-fold.
1. So I need to run code for a socket server that's all defined and created in another.py, Clicking run on PyCharm works just fine, but if you exec() the file it just runs the bottom part of the code.
There are a few answers here but they are conflicting and for Python 2.
From what I can gather there are three ways:
- Execfile(), Which I think is Python 2 code.
- os.system() (But I've seen it be said that it's not correct to pass to the OS for this)
- And subprocess.Popen (unsure how to use this either)
I need this to run in the background, it is used to create threads for sockets for the recv portion of the overall program and listen on those ports so I can input commands to a router.
This is the complete code in question:
import sys
import socket
import threading
import time
QUIT = False
class ClientThread(threading.Thread): # Class that implements the client threads in this server
def __init__(self, client_sock): # Initialize the object, save the socket that this thread will use.
threading.Thread.__init__(self)
self.client = client_sock
def run(self): # Thread's main loop. Once this function returns, the thread is finished and dies.
global QUIT # Need to declare QUIT as global, since the method can change it
done = False
cmd = self.readline() # Read data from the socket and process it
while not done:
if 'quit' == cmd:
self.writeline('Ok, bye. Server shut down')
QUIT = True
done = True
elif 'bye' == cmd:
self.writeline('Ok, bye. Thread closed')
done = True
else:
self.writeline(self.name)
cmd = self.readline()
self.client.close() # Make sure socket is closed when we're done with it
return
def readline(self): # Helper function, read up to 1024 chars from the socket, and returns them as a string
result = self.client.recv(1024)
if result is not None: # All letters in lower case and without and end of line markers
result = result.strip().lower().decode('ascii')
return result
def writeline(self, text): # Helper func, writes the given string to the socket with and end of line marker at end
self.client.send(text.strip().encode("ascii") + b'\n')
class Server: # Server class. Opens up a socket and listens for incoming connections.
def __init__(self): # Every time a new connection arrives, new thread object is created and
self.sock = None # defers the processing of the connection to it
self.thread_list = []
def run(self): # Server main loop: Creates the server (incoming) socket, listens > creates thread to handle it
all_good = False
try_count = 0 # Attempt to open the socket
while not all_good:
if 3 < try_count: # Tried more than 3 times without success, maybe post is in use by another program
sys.exit(1)
try:
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # Create the socket
port = 80
self.sock.bind(('127.0.0.1', port)) # Bind to the interface and port we want to listen on
self.sock.listen(5)
all_good = True
break
except socket.error:
print('Socket connection error... Waiting 10 seconds to retry.')
del self.sock
time.sleep(10)
try_count += 1
print('Server is listening for incoming connections.')
print('Try to connect through the command line with:')
print('telnet localhost 80')
print('and then type whatever you want.')
print()
print("typing 'bye' finishes the thread. but not the server",)
print("eg. you can quit telnet, run it again and get a different ",)
print("thread name")
print("typing 'quit' finishes the server")
try:
while not QUIT:
try:
self.sock.settimeout(0.500)
client = self.sock.accept()[0]
except socket.timeout:
time.sleep(1)
if QUIT:
print('Received quit command. Shutting down...')
break
continue
new_thread = ClientThread(client)
print('Incoming Connection. Started thread ',)
print(new_thread.getName())
self.thread_list.append(new_thread)
new_thread.start()
for thread in self.thread_list:
if not thread.isAlive():
self.thread_list.remove(thread)
thread.join()
except KeyboardInterrupt:
print('Ctrl+C pressed... Shutting Down')
except Exception as err:
print('Exception caught: %s\nClosing...' % err)
for thread in self.thread_list:
thread.join(1.0)
self.sock.close()
if "__main__" == __name__:
server = Server()
server.run()
print('Terminated')
Notes:
This is created in Python 3.4
I use Pycharm as my IDE.
One part of a whole.
2. So I'm creating a lightning detection system and this is how I expect it to be done:
- Listen to the port on the router forever
The above is done, but the issue with this is described in question 1.
- Pull numbers from a text file for sending text message
Completed this also.
- Send http get / post to port on the router
The issue with this is that i'm unsure how the router will act if I send this in binary form, I suspect it wont matter, the input commands for sending over GSM are specific. Some clarification may be needed at some point.
- Recieve reply from router and exception manage
- Listen for relay trip for alarm on severe or close strike warning.
- If tripped, send messages to phones in storage from text file
This would be the http get / post that's sent.
- Wait for reply from router to indicate messages have been sent, exception handle if it's not the case
- Go back to start
There are a few issues I'd like some background knowledge on that is proving hard to find via the old Google and here on the answers in stack.
How do I grab the receive data from the router from another process running in another file? I guess I can write into a text file and call that data but i'd rather not.
How to multi-process and which method to use.
How to send http get / post to socket on router, post needed occording to the router manual is as follows: e.g. "http://192.168.1.1/cgi-bin/sms_send?number=0037061212345&text=test"
Notes: Using Sockets, threading, sys and time on Python 3.4/Pycharm IDE.
Lightning detector used is LD-250 with RLO Relay attached.
RUT500 Teltonica router used.
Any direction/comments, errors spotted, anything i'm drastically missing would be greatly appreciated! Thank you very much in advance :D constructive criticism is greatly encouraged!
Okay so for the first part none of those suggested in the OP were my answer. Running the script as is from os.system(), exec() without declaring a new socket object just ran from __name__, this essentially just printed out "terminated", to get around this was simple. As everything was put into a classes already, all I had to do is create a new thread. This is how it was done:
import Socketthread2
new_thread = Socketthread2.Server() # Effectively declaring a new server class object.
new_thread.run()
This allowed the script to run from the beginning by initialising the code from the start in Socket, which is also a class of Clientthread, so that was also run too. Running this at the start of the parent program allowed this to run in the background, then continue with the new code in parent while the rest of the script was continuously active.