I try to make a telnet connection using subprocess, threading and pexpect modules to subscript, but I constantly fail even though manual telnet connection is available. Could you help me spot the problem? The commands should be issued in this order too "microcom /dev/ttyS3" in main script > telnet connection to subscript > "root" in subscript > "microcom /dev/ttyS6" in subscript > "Response from subscript" in subscript > "Response from main script" in main script. Bear in mind, the process of "microcom /dev/ttyS3" from main script and should remain and the whole process of subscript should be executed until the "Response from main script" is executed

Main Script:

import time
import sys
import re
import subprocess
import threading
import pexpect

# Replace with your actual COM port (e.g., COM1, COM2, etc.)
COM_Num = input("Type in COM port number: ")
COM_PORT = "COM" + COM_Num  # Adjust based on your system
BAUD_RATE = 115200  # Adjust based on your device

# Open the serial connection

ser = serial.Serial(COM_PORT, baudrate=BAUD_RATE, timeout=2)
# Send 'root' command and press Enter to loginprint("Sending 'root' to login...") send_command("root")  
# Send the 'root' commandprint("Sent 'root', now waiting for Enter...") send_command("")  
# Send Enter (empty command simulates pressing Enter)
print(f"Successfully connected to {COM_PORT} at {BAUD_RATE} baud rate.")


# Function to send command and receive response
def send_command(command):
    print(f"Sending command: {command}")
    ser.write((command + '\n').encode())  # Send command (make sure to encode as bytes)
    time.sleep(1)  # Give the device time to process
    response = ser.readlines()  # Read the response (might need to adjust this depending on the device)
    response = [line.decode('utf-8').strip() for line in response]  # Decode bytes to string
    return response

def extract_ip(response):
    ip_pattern = r"\d+\.\d+\.\d+\.\d+"  # Regular expression to match an IP address
    for line in response:
        match = re.search(ip_pattern, line)
        if match:
            return match.group(0)
    return None

# Send command to get the IP address
response = send_command("")  # This can be the empty command or a specific one to get the IP
print("Response from device:", response)

# Extract the IP address
device_ip = extract_ip(response)
if device_ip:
    print(f"Device IP address extracted: {device_ip}")
else:
    print("No IP address found in the response.")
    sys.exit(1)  # Exit if no IP address is found

# Root command to be sent
root_command = 'root'
response = send_command(root_command)
response = send_command("microcom /dev/ttyS3")
def run_telnet_commands():
    max_retries = 3
    retry_delay = 2  # seconds

    for attempt in range(max_retries):
        try:
            print(f"Attempting to establish Telnet connection (attempt {attempt + 1}/{max_retries})...")

            # First verify device is reachable
            ping_result = subprocess.run(['ping', '-n', '1', device_ip], capture_output=True, text=True)

            if "Reply from" not in ping_result.stdout:
                print(f"Device {device_ip} is not responding to ping. Waiting {retry_delay} seconds...")
                time.sleep(retry_delay)
                continue

            # Start telnet3.py using pexpect, passing the IP address to it
            print(f"Starting telnet3.py to connect to {device_ip}...")
            telnet_script = pexpect.spawn(f"python telnet3.py {device_ip}", timeout=30)
            telnet_script.logfile = sys.stdout  # Optional: Log all output for debugging
            
            # Expect the end of telnet3.py and capture the output
            telnet_script.expect("Telnet script finished.")
            telnet_script.close()

            break  # Exit after successful connection and command execution

        except Exception as e:
            print(f"Error establishing Telnet connection: {e}")
            if attempt < max_retries - 1:
                print(f"Retrying in {retry_delay} seconds...")
                time.sleep(retry_delay)
            else:
                print("Failed to establish Telnet connection after maximum retries.")
                return
    else:
        print("Failed to establish Telnet connection after maximum retries.")
        return

# Run the Telnet commands
if __name__ == "__main__":
    run_telnet_commands()
    
sys.stdout.write('Press Enter to exit.')
sys.stdin.readline()
sys.exit(0)

subscript:

import time
import sys

# Device connection parameters (this will now take the IP as a command-line argument)
if len(sys.argv) < 2:
    print("Error: No IP address provided!")
    sys.exit(1)

HOST = sys.argv[1]  # Get the IP address passed from the base script
PORT = 24            # Telnet default port (can use 23 if that’s what the device uses)
TIMEOUT = 2          # Timeout for expect commands

# Login credentials
USERNAME = "root"     # Assuming the username is "root"

COMMAND_2 = "microcom /dev/ttyS6"  # Command 2 to send after logging in
response = "response from terminal two"  # The response to send after command execution

def telnet_connect():
    try:
        # Establish Telnet connection with pexpect
        print(f"Connecting to {HOST}:{PORT}...")
        tn = pexpect.spawn(f"telnet {HOST} {PORT}", timeout=TIMEOUT)

        # Expect login prompt and send the username
        tn.expect("login: ")
        tn.sendline(USERNAME)

        # Give the system some time to respond
        tn.expect("# ")  # Expect the prompt after login (adjust if necessary)

        # Execute the second command (microcom)
        tn.sendline(COMMAND_2)
        tn.expect("# ")  # Wait for prompt after executing command

        # Send response back from terminal 2
        tn.sendline(response)
        tn.expect("# ")  # Wait for prompt after executing command

        # Capture and return the output
        output = tn.before.decode('ascii')  # Grab everything before the last prompt
        print("Command executed successfully. Output captured:")
        print(output)

        # Close the Telnet session
        tn.sendline("exit")  # Send 'exit' to close the session
        tn.close()

        return output
    
    except Exception as e:
        print(f"Error during Telnet connection: {e}")
        sys.exit(1)  # Exit the script if there's an error

# Connect to the device and run the commands
if __name__ == "__main__":
    result = telnet_connect()
    print("Telnet script finished.")```