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 there a way to integrate netstat output with python

User · Answer

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    gt  max threads       sleep 1   print final      Live Demo

User · Answer

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

User · Answer

Agree with Sachin  Just one improvement  use connect ex instead of connect  which can avoid try except  gt  gt  gt  def port check ip port           s   socket socket socket AF INET  socket SOCK STREAM          s settimeout 1          r   s connect ex ip port          return r    0       gt  gt  gt  port check loc  True  gt  gt  gt  port check loc x  False  gt  gt  gt  loc   10 3 157 24   6443   gt  gt  gt

User · Answer

In the Above I found multiple solutions But some solutions having a hanging issue or taking to much time in case of the port was not opened Below solution worked for me   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  quot 127 0 1 1 quot

User · Answer

If you only care about the local machine  you can rely on the psutil package  You can either    Check all ports used by a specific pid   proc   psutil Process pid  print proc connections    Check all ports used on the local machine   print psutil net connections      It works on Windows too   https   github com giampaolo psutil

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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 - gt 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

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

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