How to check if a network port is open on linux?

Question

How can I know if a certain port is open/closed on linux ubuntu, not a remote system, using python? How can I list these open ports in python?

• Netstat: Is th

Answer 1

Just added to mrjandro's solution a quick hack to get rid of simple connection errors / timeouts.

You can adjust the threshold changing max_error_count variable value and add notifications of any sort.

import socket

max_error_count = 10

def increase_error_count():
    # Quick hack to handle false Port not open errors 
    with open('ErrorCount.log') as f:
        for line in f:
            error_count = line
    error_count = int(error_count)
    print "Error counter: " + str(error_count)
    file = open('ErrorCount.log', 'w')
    file.write(str(error_count + 1))
    file.close()
    if error_count == max_error_count:
        # Send email, pushover, slack or do any other fancy stuff
        print "Sending out notification"
        # Reset error counter so it won't flood you with notifications
        file = open('ErrorCount.log', 'w')
        file.write('0')
        file.close()

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(2) 
result = sock.connect_ex(('127.0.0.1',80))
if result == 0:
        print "Port is open"
else:
        print "Port is not open"
        increase_error_count()

And here you find a Python 3 compatible version (just fixed print syntax):

import socket

max_error_count = 10

def increase_error_count():
    # Quick hack to handle false Port not open errors
    with open('ErrorCount.log') as f:
        for line in f:
            error_count = line
    error_count = int(error_count)
    print ("Error counter: " + str(error_count))
    file = open('ErrorCount.log', 'w')
    file.write(str(error_count + 1))
    file.close()
    if error_count == max_error_count:
        # Send email, pushover, slack or do any other fancy stuff
        print ("Sending out notification")
        # Reset error counter so it won't flood you with notifications
        file = open('ErrorCount.log', 'w')
        file.write('0')
        file.close()

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(2) 
result = sock.connect_ex(('127.0.0.1',80))
if result == 0:
        print ("Port is open")
else:
        print ("Port is not open")
        increase_error_count()