Port: 30000 already in use with multiple connections on Linux

[amirtronix]

I have a class with a plc member. I have a thread that sends a counter to MAIN.iCamClk. I have another node which writes to a struct. The codes works well without the clock thread but as soon as I try to run the thread I get:

2024-09-13T13:52:04-0700 Warning: Port: 30000 already in use as 0x7f282fffdf80

[chrisbeardy]

Hi can you please provide a sample of your code that can reproduce the error, thanks.

[amirtronix]

Here's my python code:

import threading
import pyads
import time

REMOTE_ADS = "X.X.X.X.1.1"
PLC_PORT = 851
REMOTE_IP = "X.X.X.X"

class PlcServer(threading.Thread):
    def __init__(self):
        super().__init__()
        self._stop_event = threading.Event()
        print("PLC Server initiated!")

        self.plc = pyads.Connection(REMOTE_ADS, int(PLC_PORT), REMOTE_IP)
        self.clkCounter = 0
        self.sequence = 0

        
        self.structure_def = (
                ("arrSeqData", pyads.PLCTYPE_INT, 2),
                ("bActivated", pyads.PLCTYPE_BOOL, 1)       
            )
        
        try:
            self.plc.open()
            print(f"PLC connected at AMS Address {REMOTE_ADS}")
            time.sleep(1)
            self.stLinuxData     = self.plc.get_symbol("MAIN.stLinuxData", structure_def=self.structure_def,  array_size=1)
            self.iLinuxClk       = self.plc.get_symbol("MAIN.iLinuxClk")
            self.isPlcConnected = True

        except Exception as inst:
            d = inst
            print(d)
            print(f"AMS Address {REMOTE_ADS} not found!")
            self.isPlcConnected = False


    def send_cmd(self):
        if self.isPlcConnected:
            try:
                self.stLinuxData.write([
                    {
                        "arrSeqData": [self.sequence, self.sequence],
                        "bActivated": True
                        }
                    ])
                self.sequence += 1
                        
            except:
                print(f"Connection lost with {REMOTE_ADS}!")
                print("Trying to reconnect ...")
                self._reconnect()
                time.sleep(0.5)


    def _reconnect(self):
        try:
            self.plc.close()
            self.plc.open()
            self.plc.read_state()
            self.isPlcConnected = True
            print(f"PLC reconnected at AMS Address {REMOTE_ADS}")
        except:
            self.isPlcConnected = False

    def stop(self):
        self._stop_event.set()

    def stopped(self):
        return self._stop_event.is_set()
    
    def run(self):
        while not self._stop_event.is_set():
            self.clkCounter += 1
            time.sleep(0.005)
            self.iLinuxClk.write(self.clkCounter)
            if self.clkCounter == 60000:
                self.clkCounter = 0


    def __del__(self):
        try:
            self.plc.close()
            if self.is_alive():
                self.join()
        except:
            pass



if __name__ == "__main__":

    plc_server = PlcServer()
    plc_server.start()

    try:
        while True:
            plc_server.send_cmd()
            time.sleep(0.5)

    
    except KeyboardInterrupt:
        print("Shutting down")


    finally:
        plc_server.stop()
        plc_server.join()

And here's the Plc stuct ST_LinuxData:

{attribute 'pack_mode':='1'}
TYPE ST_LinuxData :
STRUCT
	arrSeqData : ARRAY[0..1] OF INT;
	bActicated : BOOL;
END_STRUCT
END_TYPE

And my PLC.MAIN:

PROGRAM MAIN
VAR
	stLinuxData : ST_LinuxData;
	iLinuxClk	: UINT;
	bStart : BOOL;		
END_VAR

Everything works fine as long as I have TwinCAT open on a laptop, however, as soon as I open the TwinCAT on PLC or connect an HMI as a new ads client, I get 'Port: 30000 already in use as 0x7ffe9a7eba50' error.

[chrisbeardy]

I think this may be linked to #422 and #423 as I just tested this on windows and works fine there. You may need to come up with a workaround for this as its an underlying ADS issue, see the discussion threads. It may also be worth trying a different threading style, currently you're missing the self.cmd() method from the main thread, but it's using the ADS connection on the second thread. You are better off having one ADS connection per thread, this may solve the issue.