Develop Reference

Connection time out on sockets

Good day everyone! I'm still doing research on this so please pardon if I make any mistake. I'm currently working on a small project that need socket connection between 2 device, problem is, when ever I used the client and the server on the same device, it worked out okay. But when I moved the client into a different device, then started the process again(same LAN connection), it just gave me the time out error [WinError 10060]. Here is my code:
Server side:
HOST = '10.0.0.32'
PORT = 44132
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind((HOST, PORT))
server.listen()
client, address = server.accept()
Client side:
HOST = '10.0.0.32'
PORT = 44132
client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client.connect((HOST, PORT))
I have tried disabling the Firewall and restart computer, changing port or trying to check in cmd if server is really Listening or not, is there anything that I'm missing here? Thank you.
The full error report is: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond
edit:
Here is also my port listening on 44132 using netstat:
Proto Local Address Foreign Address State
TCP 0.0.0.0:44132 0.0.0.0:* LISTENING
edit2: Another update on my end, I've tried turning off the firewall on target machine and ping it, the ping now went through successfully but the client and server still refused to reconnect and continue on timing out. Could it be that there is another firewall between my 2 devices and are implemented by the router to prevent the connection taking place?

Probably you are using the wrong ip address, my advice is to use the command arp -a to check if the server's ip is correct (if you have access to the router you could check there otherwise).
Moreover, be aware when you use socket.gethostbyname(socket.gethostname()), take a look here Python socket.gethostname

Peer to peer socket communication without port forwarding

First of all I am not talking about a tcp or udp or socket implemented in a vps or server
My question is just like client to client socket communication.
Imagine listening at your home pc with a tcp socket. You can connect to this from home inter network anyway. But suppose someone wants to connect to it via the internet. Then you can create a forwarding rule on the router and bring it to working condition. Then the router knows that if an incoming connection comes from a port, the connection will be forwarded to the device in the relevant inter network.
But the ISP I use does not support port forwarding.
I thought these were not impossible because of the team-viewer software. Because when I was connected to a friend in team-viewer, I opened the wire-shark and reviewed it.
Then I saw that the data packet is exchanged peer to peer. Because the destination source addresses were my ip and friend's ip
This means that the video data is exchanged without the participation of an additional server
I highlighted the team-viewer connection.
61.245.175.81 is my friend's public IP. 192.168.1.130 is my internal IP
I want to do the same
Here is my simple socket code. This does not work through the internet because there is no router forwarding rule. I am very new to socket and networking side
Sever
import socket
server_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server_socket.bind(('', 12000))
while True:
message, address = server_socket.recvfrom(1024)
message = repr(message)
print("Connected from -> " + str(address) )
print("Received data -> " + message)
reply = b"Hi from server :) "
server_socket.sendto(reply, address)
Client
import time , datetime
import socket
client_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
client_socket.settimeout(1.0)
message = bytes(str(datetime.datetime.now()),'utf-8')
addr = ("192.168.1.130", 12000)
client_socket.sendto(message, addr)
try:
data, server = client_socket.recvfrom(1024)
print( repr(data) )
except: #socket.timeout:
print('REQUEST TIMED OUT')
Can anyone give an explanation for my question

Pretty sure they do it using UDP hole punching, you'd need to do something similar to implement this.
In a nutshell two clients behind NAT (which is what your router is doing) can use a third server acting as a sort of mediator to establish a connection.

Python socket connection not working over Local Network

I'm trying to get two computers (my PC and my laptop) to communicate over the Local Network using the Socket module in python.
This is the Server side code running on my PC (connected via LAN):
import socket
HOST = '192.168.1.3' #local PC IP
print(HOST)
PORT = 8080 # Port to listen on (non-privileged ports are > 1023)
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
s.bind((HOST, PORT))
s.listen()
conn, addr = s.accept()
with conn:
print('Connected by', addr)
while True:
data = conn.recv(1024)
print(data)
if not data:
break
conn.sendall(data)
And this is the Client side code, running on my Laptop (connected over WiFi):
import socket
TCP_IP = '192.168.1.3'
TCP_PORT = 8080
BUFFER_SIZE = 1024
MESSAGE = b"Hello, World!"
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((TCP_IP, TCP_PORT))
s.send(MESSAGE)
data = s.recv(BUFFER_SIZE)
s.close()
print("received data:", data)
The thing is: when I execute both codes, the Server side stays idle waiting for a connection and the Client side, after a while stops and returns the following timeout error:
Traceback (most recent call last):
File "C:\Users\...\client.py", line 13, in <module>
s.connect((TCP_IP, TCP_PORT))
TimeoutError: [WinError 10060] A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond
I can't understand why it won't connect from another device in the same network while it works perfectly if I execute the Client code on the same machine as the Server, even if when I run netstat -an in the CMD I can see the computer listening on that port:
TCP 192.168.1.3:8080 0.0.0.0:0 LISTENING
I tough it had something to do with the port forwarding so I tried playing around with it but I'm having troubles with that too (the ports seem to remain closed).
I really don't know what to do next, if you have some advice or know something else I could try please reply.

It actually was a firewall problem, I just needed to disable the windows defender firewall for the local network and now everything is working fine

In Windows 10, I had to open the port I was using for the socket, and it worked for me.
Here is a link to the instructions.

You're listening and connecting to the same IP - you need to listen to the client's IP(or just any IP with the correct port number) on the server and connect to the server's IP on the client.
For example, if the client's IP is 1.2.3.4 and the server's is 1.2.3.5, then
# server side
s.bind(('1.2.3.4', 8080)) # CLIENT_IP = '1.2.3.4'; PORT = 8080
# can also be s.bind(('0.0.0.0', 8080)) if you want multiple clients to connect.
# client side
s.connect(('1.2.3.5', 8080)) # SERVER_IP = '1.2.3.5'; PORT = 8080

Python3 TCP Server not seeing incoming messages from external device

I want to create a small TCP server that takes incoming TCP connections from a device that is hooked up via Ethernet to my computer.
The physical port for that has the IP 192.168.1.100 statically assigned to it.
The scripts I use as a client and server are listed at the bottom.
The setup works if I want to send messages between the python scripts. However, I am unable to receive anything from the external device (screenshot from Wireshark capture below). From what I have read I can define an interface to listen to by defining its IP. So I defined the IP of the interface as the host variable. However, I do not receive anything in my script but the messages sent by the other script. I had a similar situation already here on stackoverflow. I thought that defining the correct IP as the host would resolve this issue but it did not.
I am also having a hard time capturing the traffic between the two scripts with Wireshark at all. They did not show up anywhere.
I need to pick up these connections on the eth0 interface with the static IP 192.168.1.100:
tcp_server.py
import socket
# create a socket object
serverSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# get local machine name
# host = socket.gethostname()
host = "192.168.1.100"
port = 9002
# bind to the port
serverSocket.bind((host, port))
# queue up to 5 requests
serverSocket.listen(5)
while True:
# establish a connection
clientSocket, addr = serverSocket.accept()
print("Got a connection from %s" % str(addr))
msg = 'Thank you for connecting' + "\r\n"
clientSocket.send(msg.encode('ascii'))
clientSocket.close()
and this as a client:
tcp_client.py
import socket
# create a socket object
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
# get local machine name
# host = socket.gethostname()
host = "192.168.1.100"
port = 9002
# connection to hostname on the port.
s.connect((host, port))
# Receive no more than 1024 bytes
msg = s.recv(1024)
s.close()
print(msg.decode('ascii'))

Hijacking a client socket

I have set up a server socket (plain raw socket) listening on port A. A client now connects to this server. OS opens up a port for the client for this purpose. Say port B is allocated to this client. Now my question is, can a 3rd script connect to this port B and send data. Or in other words can I spoof a response to the client as if it was coming from the server? I tried spoofing it using scapy, but it wasnt working.
server.py
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(("localhost", A))
s.listen(10)
ns, cli_addr = s.accept()
time.sleep(30) # so that i can trigger my 3rd script
goodclient.py
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("localhost", A))
print s.getsockname() # to get the local port of client - B
s.recv(1024)
badboy.py
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("localhost", B)) # connection refused error
s.send("hihihi")
scapybadboy.py
pack = IP(src="localhost", dst="localhost") / TCP(sport=A, dport=B) / "Hello"
send(pack) # Packet sent but not received by the client

Because server and client using SOCK_STREAM sockets, they both aware of TCP session(including port, IP and (SEQ_NUMBER,ACK_NUMBER)), so when session is already in process, you will have to perform TCP hikacking and IP spoofing in order to send messages in stream.
In other words, you will have to guess(or steal) ACK number of server in order to send fake messages to client using badclient.
However, if you will make somehow goodclient answer you and not a server you should run the following:
iptables -A FORWARD -j NFQUEUE --queue-num 1 , because your operating system doesn't know about session that you just "opened" with goodclient and it will send RST packet. This command will prevent it.