如何检查网络端口是否打开？

You can using the socket module to simply check if a port is open or not.

It would look something like this.

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

Netstat tool simply parses some /proc files like /proc/net/tcp and combines it with other files contents. Yep, it's highly platform specific, but for Linux-only solution you can stick with it. Linux kernel documentation describes these files in details so you can find there how to read them.

Please also notice your question is too ambiguous because "port" could also mean serial port (/dev/ttyS* and analogs), parallel port, etc.; I've reused understanding from another answer this is network port but I'd ask you to formulate your questions more accurately.

If you only care about the local machine, you can rely on the psutil package. You can either:

1. Check all ports used by a specific pid:

   proc = psutil.Process(pid)
   print proc.connections()
   

2. Check all ports used on the local machine:

   print psutil.net_connections()
   

It works on Windows too.

https://github.com/giampaolo/psutil

Just added to mrjandro's solution some improvements like automatic resource management (making sure that the opened socket also gets closed), handling timeouts, getting rid of simple connection errors / timeouts and printing out results:

import socket
from contextlib import closing


hosts = ["host1", "host2", "host3"]
port = 22
timeout_in_seconds = 2


hosts_with_opened_port = []
hosts_with_closed_port = []
hosts_with_errors = []




def check_port(host, port, timeout_in_seconds):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(timeout_in_seconds)
with closing(socket.socket(socket.AF_INET, socket.SOCK_STREAM)) as sock:
try:
result = sock.connect_ex((host, port))
if result == 0:
print("Port {} is *** OPEN *** on host: {}".format(port, host))
hosts_with_opened_port.append(host)
else:
print("Port {} is not open on host: {}".format(port, host))
hosts_with_closed_port.append(host)
except socket.gaierror:
print("Port {} check returns a network *** ERROR *** on host: {}".format(port, host))
hosts_with_errors.append(host)




for host in hosts:
check_port(host, port, timeout_in_seconds)


print("\nHosts with opened port:")
print(hosts_with_opened_port)
print("\nHosts with closed port:")
print(hosts_with_closed_port)
print("\nHosts with errors:")
print(hosts_with_errors)

If you want to use this in a more general context, you should make sure, that the socket that you open also gets closed. So the check should be more like this:

import socket
from contextlib import closing
   

def check_socket(host, port):
with closing(socket.socket(socket.AF_INET, socket.SOCK_STREAM)) as sock:
if sock.connect_ex((host, port)) == 0:
print("Port is open")
else:
print("Port is not open")

For me the examples above would hang if the port wasn't open. Line 4 shows use of settimeout to prevent hanging

import socket


sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(2)                                      #2 Second Timeout
result = sock.connect_ex(('127.0.0.1',80))
if result == 0:
print 'port OPEN'
else:
print 'port CLOSED, connect_ex returned: '+str(result)

In case when you probing TCP ports with intention to listen on it, it’s better to actually call listen. The approach with tring to connect don’t 'see' client ports of established connections, because nobody listen on its. But these ports cannot be used to listen on its.

import socket




def check_port(port, rais=True):
""" True -- it's possible to listen on this port for TCP/IPv4 or TCP/IPv6
connections. False -- otherwise.
"""
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.bind(('127.0.0.1', port))
sock.listen(5)
sock.close()
sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
sock.bind(('::1', port))
sock.listen(5)
sock.close()
except socket.error as e:
return False
if rais:
raise RuntimeError(
"The server is already running on port {0}".format(port))
return True

Please check Michael answer and vote for it. It is the right way to check open ports. Netstat and other tools are not any use if you are developing services or daemons. For instance, I am crating modbus TCP server and client services for an industrial network. The services can listen to any port, but the question is whether that port is open? The program is going to be used in different places, and I cannot check them all manually, so this is what I did:

from contextlib import closing
import socket
class example:
def __init__():


self.machine_ip = socket.gethostbyname(socket.gethostname())
self.ready:bool = self.check_socket()


def check_socket(self)->bool:
result:bool = True
with closing(socket.socket(socket.AF_INET, socket.SOCK_STREAM)) as sock:
modbus_tcp_port:int = 502
if not sock.connect_ex((self.machine_ip, modbus_tcp_port)) == 0:
result = False
return result

Here's a fast multi-threaded port scanner:

from time import sleep
import socket, ipaddress, threading


max_threads = 50
final = {}
def check_port(ip, port):
try:
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # TCP
#sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) # UDP
socket.setdefaulttimeout(2.0) # seconds (float)
result = sock.connect_ex((ip,port))
if result == 0:
# print ("Port is open")
final[ip] = "OPEN"
else:
# print ("Port is closed/filtered")
final[ip] = "CLOSED"
sock.close()
except:
pass
port = 80
for ip in ipaddress.IPv4Network('192.168.1.0/24'):
threading.Thread(target=check_port, args=[str(ip), port]).start()
#sleep(0.1)


# limit the number of threads.
while threading.active_count() > max_threads :
sleep(1)


print(final)

Live Demo

Building upon the psutil solution mentioned by Joe (only works for checking local ports):

import psutil
1111 in [i.laddr.port for i in psutil.net_connections()]

returns True if port 1111 currently used.

psutil is not part of python stdlib, so you'd need to pip install psutil first. It also needs python headers to be available, so you need something like python-devel

I found multiple solutions in this post. But some solutions have a hanging issue or takeing too much time in case of the port is not opened.Try below solution :

import socket


def port_check(HOST):
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(2) #Timeout in case of port not open
try:
s.connect((HOST, 22)) #Port ,Here 22 is port
return True
except:
return False


port_check("127.0.1.1")

Agree with Sachin. Just one improvement, use connect_ex instead of connect, which can avoid try except

>>> def port_check(ip_port):
...     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
...     s.settimeout(1)
...     return s.connect_ex(ip_port) == 0
...
>>> port_check(loc)
True
>>> port_check(loc_x)
False
>>> loc
('10.3.157.24', 6443)
>>>

This will find a random port in the given range:

import socket
import random
from typing import Tuple


def find_listening_port(
port_range:Tuple[int,int]=None,
host='',
socket_type='tcp',
default:int=None
) -> int:
"""Find an available listening port
    

Arguments:
port_range: Optional tuple of ports to randomly search, ``[min_port, max_port]``
If omitted, then randomly search between ``[6000, 65534]``
host: Host interface to search, if omitted then bind to all interfaces
socket_type: The socket type, this should be ``tcp`` or ``udp``
default: The port to try first before randomly searching the port range


Returns:
Available port for listening
"""
def _test_port(host, port, socket_protocol):
with socket.socket(socket.AF_INET, socket_protocol) as sock:
try:
sock.bind((host, port))
if socket_type == 'tcp':
sock.listen(1)
return port
except:
pass


return -1


if port_range is None:
port_range = (6000,65534)


if socket_type == 'tcp':
socket_protocol = socket.SOCK_STREAM
elif socket_type == 'udp':
socket_protocol = socket.SOCK_DGRAM
else:
raise Exception('Invalid socket_type argument, must be: tcp or udp')


searched_ports = []
if default is not None:
port = _test_port(host, default, socket_protocol)
if port != -1:
return port
searched_ports.append(default)


for _ in range(100):
port = random.randint(port_range[0], port_range[1])
if port in searched_ports:
continue


port = _test_port(host, port, socket_protocol)
if port != -1:
return port


searched_ports.append(port)


raise Exception(f'Failed to find {socket_type} listening port for host={host}')

Example usage:

# Find a TCP port,
# first check if port 80 is availble
port = find_listening_port(
port_range=(4000, 60000),
host='',
socket_type='tcp',
default=80
)
print(f'Available TCP port: {port}')