Portscanner, host and list of ports

Code was taken from Violent Python book

Author: geekcomputers

portscanner.py

@@ -0,0 +1,61 @@
+# Script Name	: portscanner.py
+# Author		: Craig Richards
+# Created		: 20 May 2013 
+# Last Modified	: 
+# Version		: 1.0
+
+# Modifications	: 
+
+# Description	: Port Scanner, you just pass the host and the ports
+
+import optparse				# Import the module
+from socket import *		# Import the module
+from threading import *		# Import the module
+
+screenLock = Semaphore(value=1)		# Prevent other threads from preceeding
+
+def connScan(tgtHost, tgtPort):		# Start of the function
+	try:
+		connSkt = socket(AF_INET, SOCK_STREAM)	# Open a socket
+		connSkt.connect((tgtHost, tgtPort))
+		connSkt.send('')
+		results=connSkt.recv(100)
+		screenLock.acquire()		# Acquire the lock
+		print '[+] %d/tcp open'% tgtPort
+		print '[+] ' + str(results)
+	except:
+		screenLock.acquire()
+		print '[-] %d/tcp closed '% tgtPort
+	finally:
+		screenLock.release()
+		connSkt.close()
+		
+def portScan(tgtHost, tgtPorts):	# Start of the function
+	try:
+		tgtIP = gethostbyname(tgtHost)	# Get the IP from the hostname
+	except:
+		print "[-] Cannot resolve '%s': Unknown host"%tgtHost
+		return
+	try:
+		tgtName = gethostbyaddr(tgtIP)	# Get hostname from IP
+		print '\n[+] Scan Results for: ' +tgtName[0]
+	except:
+		print '\n[+] Scan Results for: ' + tgtIP
+	setdefaulttimeout(1)
+	for tgtPort in tgtPorts:	# Scan host and ports
+		t = Thread(target=connScan, args=(tgtHost, int(tgtPort)))
+		t.start()
+
+def main():
+	parser = optparse.OptionParser('usage %prog -H'+' <target host> -p <target port>')
+	parser.add_option('-H', dest='tgtHost', type='string', help='specify target host')
+	parser.add_option('-p', dest='tgtPort',type='string', help='specify target port[s] seperated by a comma')
+	(options, args) = parser.parse_args()
+	tgtHost = options.tgtHost
+	tgtPorts = str(options.tgtPort).split(',')
+	if (tgtHost == None) | (tgtPorts[0] == None):
+		print parser.usage
+		exit(0)
+	portScan(tgtHost, tgtPorts)
+if __name__ == '__main__':
+	main()