python2.7 netcat program running with subprocesses - python-2.7

Question

I am trying to make a script to mimic netcat and it kinda runs but i don't get the result i'm meant to, when trying to debug it i managed to do a bit but after days of searching and trial and errors i am at a loss at how to fix the issue. This is my whole code:
import sys
import socket
import getopt
import threading
import subprocess
import os
# define the global variables
listen = False
command = False
upload = False
execute = ""
target = ""
upload_destination = ""
port = 0
def usage():
print "BHP Net Tool"
print "Usage: netcat2.py -t target_host -p port"
print "-l --listen - listen on [host]:[port] for incoming
connections"
print "-e --execute=file_to_run - execute the given file upon receiving
a connection"
print "-c --command - initialize a command shell"
print "-u --upload=destination - upon receiving connection upload a
file and wrtie to [destination]"
print "Examples: "
print "netcat2.py -t 192.168.0.1 -p 5555 -l -c"
print "netcat2.py -t 192.168.0.1 -p 5555 -l -u=C:\\target.exe"
print "netcat2.py -t 192.168.0.1 -p 5555 -l -e=\"cat /etc/passwd\""
print "echo 'ABCDEFGHI' | ./netcat2.py -t 192.168.0.1 -p 135"
sys.exit(0)
def main():
global listen
global port
global execute
global command
global upload_destination
global target
if not len(sys.argv[1:]):
usage()
# read the commandline option
try:
opts, args = getopt.getopt(sys.argv[1:], "hle:t:p:cu", ["help",
"listen", "execute", "target", "port", "command", "upload"])
except getopt.GetoptError as err:
print str(err)
usage()
for o, a in opts:
if o in ("-h", "--help"):
usage()
elif o in ("-l", "--listen"):
listen = True
elif o in ("-e", "--execute"):
execute = a
elif o in ("-c", "--commandshell"):
command = True
elif o in ("-u", "--upload"):
upload_destination = a
elif o in ("-t", "--target"):
target = a
elif o in ("-p", "--port"):
port = int(a)
else:
assert False, "Unhandled Option"
# are we going to listen or just send data from stdin?
if not listen and len(target) and port > 0:
# read in the line from the commandline
# this will block, so send CTRL-D if not sending input
# to stdin
line = sys.stdin.readline()
print (line)
# send data off
client_sender(line)
# we are going to listen and potentially
# upload things, execute commands, and drop a shell back
# depending on our command line options above
if listen:
server_loop()
def client_sender(line):
client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
# connect to our target host
client.connect((target, port))
if len(line):
client.send(line)
while True:
# now wait for data back
recv_len = 1
response = ""
while recv_len:
data = client.recv(4096)
recv_len = len(data)
response += data
if recv_len < 4096:
break
print "response"
# wait for more input
line = raw_input("")
line += "\n"
# send it off
client.sendline()
except:
print "[*] Exception! Exiting."
# tear down the connection
client.close()
def server_loop():
global target
# if no target is defined, we listen on all interfaces
if not len(target):
target = "0.0.0.0"
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind((target, port))
server.listen(5)
while True:
client_socket, addr = server.accept()
# spin off a thread to handle out new client
client_thread = threading.Thread(target=client_handler, args=
(client_socket,))
client_thread.start()
def run_command(command):
# trim the newline
command = command.rstrip()
# run the command and get the output back
try:
with open(os.devnull, 'w') as devnull:
output = subprocess.check_output(command,
stderr=subprocess.STDOUT, shell=True)
except:
output = "Failed to execite command. \r\n"
# send the output back to the client
return output
def client_handler(client_socket):
global upload
global execute
global command
# check for upload
if len(upload_destination):
# read in all of the bytes and write to out destination
file_line = ""
# keep reading data until none is available
while True:
data = client_socket.recv(1024)
if not data:
break
else:
file_line += data
# now we take these bytes and try to write them out
try:
file_descriptor = open(upload_destination, "wb")
file_descriptor.write(file_line)
file_descriptor.close()
# acknowledge that we wrote the file out
client_socket.send("Succesfully saved file to %s\r\n" %
upload_destination)
except:
client_socket.send("Failed to save file to %s\r\n" %
upload_destination)
# check for command execution
if len(execute):
# run the command
output = run_command(execute)
client_socket.send(output)
# now we go into another loop if a command shell was requested
if command:
while True:
# show a simple prompt
client_socket.send("<BHP:#> ")
# now we receive until we see a linefeed (enter key)
cmd_line = ""
while "\n" not in cmd_line:
cmd_line += client_socket.recv(1024)
# send back the command output
response = run_command(cmd_line)
# send back the response
client_socket.send(response)
main()
when i run it, and close it with CTRL+D it exits and when i close the terminal i get this message in localhost:
<BHP:#> Failed to execite command.
<BHP:#>
if anyone can help me fix this or even point me in the right direction i'd really appreciate it :), i'm trying to run this in python 2.7