Connection refused trying to connect to server

Question

I am playing around with a little netcat tool of my own, but I keep getting "Connection refused" and a reference to a specific line, I've highlighted that below.

First I run the server, with the following command: python Netstatx.py -l -p 9999 -c

Then I run the "client" which tries to make a connection to the server, which is listening on port 9999: python Netstatx.py -t localhost -p 9999

As mentioned, the above gives me an "Connected refused"-exception, how come?

import sys
import socket
import getopt
import threading
import subprocess

# Define globals
listen = False
command = False
upload = False
execute = ""
target = ""
upload_destination = ""
port = 0

def usage():

    print "Netstatx - Net Tool for your convenience"
    print
    print "Usage: Netstatx.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 write to 
                                          [destination]"
    print
    print
    print "Examples: "
    print "Netstatx.py -t 192.168.0.1 -p 5555 -l -c"
    print "Netstatx.py -t 192.168.0.1 -p 5555 -l -u=\\target.exe"
    print "Netstatx.py -t 192.168.0.1 -p 5555 -l -e=\"cat /etc/passwd\""
    sys.exit(0)

def client_sender(buffer):

    client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    print "%s:%s" % (target, port)
    # Connect to our target host
    **client.connect((target, port))** <-- This is failing.

    if len(buffer):
        client.send(buffer)

    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
        buffer = raw_input("")
        buffer += "\n"

        # Send it off
        client.send(buffer)

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 our new client
        client_thread = threading.Thread(target=client_handler, 
                                         args=(client_socket,))
        client_thread.start()


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 options
    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?
# if not listen and len(target) and port > 0

        # Read in the buffer from the commandline
        # this will block, so send CTRL-D if not sending input
        # to stdin
        buffer = sys.stdin.read()

        # Send data off
        client_sender(buffer)

        # 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()
main()


def run_command(command):

    # trim the newline
    command = command.rstrip()

    # Run the command and get the output back
    try:
        output = subprocess.check_output(command, 
        stderr=subprocess.STDOUT, shell=True)
    except:
        output = "Failed to execute command. \r\n"

    # Send the output back to the client return output
    return output

def client_handler(client_socket):
    global upload
    global execute
    global command

    # Check for upload
    if len(upload_destination):

        # Read on all of the bytes and write to our destination
        file_buffer = ""

        # Keep reading data until none is available
        while True:
            data = client_socket.recv(1024)

            if not data:
                break
            else:
                file_buffer += data
        # Now we take these bytes and try to write them out
        try:
            file_descriptor = open(upload_destination, "wb")
            file_descriptor.write(file_buffer)
            file_descriptor.close()

            # Acknowledge that we rote the file out
            client_socket.send("Successfully 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("<Netstatx:#> ")

                # Now we receive until we see a linefeed (enter key)
                cmd_buffer = ""
                while "\n" not in cmd_buffer:
                    cmd_buffer += client_socket.recv(1024)

                # Send back the command output
                response = run_command(cmd_buffer)

                # Send back the response
                client_socket.send(response)

Answer 1

 import sys import socket import getopt import threading import subprocess #define some global variables listen = False command = False upload = False execute = "" target = "" upload_destination = "" port = 0 def usage(): print "Net Tool" print print "Usage : netcat.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 -intialize a command shell" print "-u --upload=destination -upon receiving connection upload a file and write to [destination]" print print print "Examples : " print "netcat.py -t 192.168.0.1 -p 5555 -l -c" print "netcat.py -t 192.168.0.1 -p 5555 -l -u=c:\\\\target.exe" print "netcat.py -t 192.168.0.1 -p 5555 -l -e=\\"cat /etc/passwd\\"" print "echo 'ABCDEEGHI' | ./netcat.py -t 192.168.11.12 -p 135" sys.exit(0) def run_command(command): #trim the newline command= command.rstrip() #run the command get the output back try: output = subprocess.check_output(command, stderr=subprocess.STDOUT, shell=True) except: output = "Failed to execute 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 our destination file_buffer= "" #keep reading data until none is available while True: data= client.socket.recv(1024) if not data: break else: file_buffer += data #now we take these bytes and try to write them out try: file_descriptor=open(upload_destination,"wb") file_descriptor.write(file_buffer) file_descriptor.close() #aknowledg that we wrote the file out client_socket.send("Successfully 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_buffer = "" while "\\n" not in cmd_buffer: cmd_buffer += client_socket.recv(1024) # send back the command output response = run_command(cmd_buffer) # send back the response client_socket.send(response) def client_sender(buffer): client= socket.socket(socket.AF_INET, socket.SOCK_STREAM) try: #connect to our target host client.connect((target,port)) if len(buffer): client.send(buffer) 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 buffer = raw_input("") buffer+= "\\n" # send it off client.send(buffer) except: print "[*] Exception! Exiting." 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 handl our new client client_thread= threading.Thread(target=client_handler, args=(client_socket,)) client_thread.start() 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 options 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 buffer from the cmdline #this will block, so send CTRL-D if not sending input #to stdin buffer = sys.stdin.read() client_sender(buffer) #we are goin to listen and potentially #upload things, execute commands, and drop a shell back #depending on our command line options above if listen : server_loop() main() 

I found some syntax errors running out your script ( it may be just from copy past), any way i did my small edits and it's working (knowing i'm under linux) Your problem may be the firewall is refusing connection on that port, try to check it out