Noobish socket question

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January 13th, 2004, 09:40 PM

theperfectsoup

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Noobish socket question

I feel so ignorant...

But what's the quickest/easiest way to tell if a socket is connected, i.e., open? There's gotta be some flag I can mask to check, or a really easy way...

Thanks!

- tps

January 13th, 2004, 09:53 PM

SolarBear

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Here. I suppose you have some socket knowledge so I won't go into much explaining.

Code:

import socket

s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
ip = "127.0.0.1" #change to scan another machine
port = 10000 #or whatever you wish
if not s.connect_ex((ip, port)):
  print 'Port open.'
else:
  print 'Port closed.'

connect_ex(ip,port) is a simple method that returns 0 if the connection worked or some error error number if it failed.

January 13th, 2004, 09:57 PM

theperfectsoup

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Hey, that's dandy. Because if the socket wasn't open, I wanted to open it anyway

But just for future reference, does anyone know of a simple test to check if a socket is open (without disconnecting it if it is, or connecting it if it isn't)?

Thanks for the prompt response, SolarBear =)

- tps

January 14th, 2004, 02:29 AM

netytan

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You could always wrap connect() in a try-except statment, if it doesn't connect at first you can then get a usful error message if you want. Also if you put this inside a while loop you can have it try and connect whenever the connection is dropped.

Sorry, no example for ya

Mark.

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January 14th, 2004, 02:55 PM

SolarBear

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I DO have one example - maybe not what you're looking for, but heh. Here's a simple threaded port scanner I wrote. Nothing fancy - plus it hangs if you specify too many ports

- but it works !

Code:

# Zero24's single IP port scanner V1.0
# V1.3.1 by SolarBear
import socket,thread

def scan_port(ip,port,s):
    global openports,t_number,t_lock,open_lock
    if not s.connect_ex((ip, n)):
        open_lock.acquire()
        openports.append(n)
        open_lock.release()
    s.close()
    t_lock.acquire()
    t_number -= 1
    t_lock.release()
    
ip = socket.gethostbyname(socket.gethostname()) #local IP
Sport = input("Please enter the start port number: ")
Eport = input("Please enter the end port number: ")
Eport = Eport + 1

print "You are scanning", ip
print "for ports", Sport,"to", Eport - 1

openports = []
sockets = [socket.socket(socket.AF_INET,socket.SOCK_STREAM) for i in range(Sport,Eport)]
open_lock = thread.allocate_lock()
t_number = Eport - Sport
t_lock = thread.allocate_lock()
for n in range(Sport, Eport):
    thread.start_new_thread(scan_port,(ip,n,sockets[n-Sport]))
while t_number > 0: pass
if len(openports) > 0:
    openports = sort(openports)
    print "Open ports: ",openports
else: print "No open ports. Sorry."

This does what you asked for, though : by calling connect or connect_ex, you try connection to the remote host : if it worked you stay connected and if it didn't... well you obviously can't connect anyway !

Noobish socket question

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