this code below is working fine between two computers on the same network but it doesn't work between two computers on two different networks and i have tried to use the public IP address
clint
import socket
s = socket.socket()
port = 10000
ip=input("what is ip : ")
s.connect((ip, port))
print (s.recv(1024))
s.close
server
import socket
s = socket.socket()
ip=socket.gethostbyname(socket.gethostname())
print (ip)
port = 10000
s.bind((ip, port))
s.listen(1)
while True:
c, addr = s.accept()
print ('Got connection from', addr)
c.send(bytes([int(1)]))
c.close()
this question have already been asked many times but all the answers i could found is that i have to do " port forwarding " with out any code examples how to do it in some of the answers they say i should download application that will do the port forwarding to me but i don't know how to use it then in my python code ?
Port forwarding is something you do at the router level. For example if the two computers you are trying to connect are behind two different WiFi routers at two different homes then you need to set both WiFi routers in both locations to forward port 10000 (the one you're using) to forward to the internal IP of the computer where your code is running.
Your WiFi router has a public IP (what you're probably using now) and your computers running your python code have local IPs internal to the network that are assigned by the WiFi routers. Port forwarding takes traffic going to the public IP of a router and forwards it internally in the local network to the computer at some local IP that runs your program.
In other words this is not something you will do in your code — this is something you will do in your router's software.
If you are feeling ambitious you can follow this tutorial that removes the need to configure your devices for port forwarding. Assuming you have uPNP capable routers.
https://www.electricmonk.nl/log/2016/07/05/exploring-upnp-with-python/
And there may even be a module that takes all the leg work out.(not checked how it works)
https://pypi.python.org/pypi/UPnP/1.3
Related
So far I have made a VERY basic client/server application that creates a TCP connection. I have a lot of programming experience, just never did this low-level stuff and especially nothing with networks. Note that all the prints are just to help me figuring out what is going on. One of the known issues is that jsonip sometimes gives me an IPv4 and sometimes v6, I don't know why but that doesn't matter for now, just to warn anyone who wants to recreate my code.
Server:
import socket
import requests
port = int(input("Enter port you want to open:\n"))
#todo: add errorhandling
print("Adding socket...")
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
hostname = socket.gethostname()
print(f"Hostname: {hostname}")
ip_address = socket.gethostbyname(hostname)
print(f"Host address: {ip_address}")
r = requests.get(r'http://jsonip.com')
public_ip_address = r.json()['ip']
s.bind((ip_address, port))
print("Is open for connections on IP: "+public_ip_address+" and Port: "+str(port))
s.listen(5)
print("Done initialisation, listening for incoming connections...")
while True:
clientsocket, address = s.accept()
print(f"Connection from {address} has been established")
clientsocket.send(bytes(f"You have connected to server: {hostname}", "utf-8"))
Client:
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ip = input("Enter IP to connect to:\n")
port = int(input("Enter Port to connect to:\n"))
print(f"Connecting to server {ip} ...")
s.connect((ip, port))
msg = s.recv(1024)
print(msg.decode("utf-8"))
On my local machine: Open 20000 in my server.py, it tells me the host is 127.0.1.1, I then enter 127.0.1.1 into my client script and 20000, and they connect. So the Socket has been bound with the 127.0.1.1. (Side question: What is this IP address, is it like the internal IP address of processes in my PC or something? If running ip a on my other machine it is the first one shown of 2)
Using Virtmanager on my machine and running one Linux Server (command line only) and one normal Ubuntu, the server tells me the host is, again, 127.0.1.1 which I don't need to enter into the other VM to know it won't work, what does work however, is getting the IP-address of the Server via ip a, which in this case is 192.168.122.37, and when I enter this IP address into the client, it connects. But in the socket here I bind, again, the 127.0.1.1, so is it arbitrary what I put here? What SHOULD I bind here, the public, the weird or the 192. address?
The first thing I could not get to work was using 2 physical devices. When opening a server on my Linux machine, I cannot connect with my windows machine at all, no matter if I use my public, my 127. or my 192. IP-address. Now my end goal is doing this over the internet so I am walking myself up, describing here the steps I took to try and get where I want to be but here I hit a brick wall where I don't know what is wrong. Am I binding the wrong address on the server, is my router being a problem, is there something else wrong?
I also tried leaving my network using my friends pc a few countries over, but this also just results in a timeout (my theory is that the Router port he is trying to open is closed and I have now idea how I can make the router send data to his PC, which should be not impossible as firefox and every application using internet does it without me having to manually forward every port, I just don't know how). This is my end goal, creating a connection between my friends PC and mine, and this is how far I got (I wouldn't mind skipping the local network if it is not relevant for fixing the global connection problem), so, tl;dr: what did i do wrong, what do i need to bind and what do i need to do for the final result to work?
There are many questions to answer.
Addresses 127.X.X.X are reserved for the loopback interface, most common one is 127.0.0.1. The loopback is a virtual, but important interface and as you have probably guessed, it is usable on the local machine only. You cannot use 127.X.X.X address to make two hosts to communicate with each other.
Addresses 192.168.X.X (and also 10.X.X.X and 172.16-31.X.X.) are reserved for local LANs. They are not valid on the Internet.
You cannot use these addresses to make two hosts to communicate with each other over the public Internet (unless you create a tunnel, an advanced networking topic)
Almost everybody uses them, because we ran out of IPv4 addresses long time ago, they were difficult to get, expensive, etc. Also such hosts are isolated from the Internet, they can be reached only via a router that translates addresses. Such router feature is called NAT. A typical router has one valid Internet address and all connections to the Internet appear as coming from the router. If you contant a service like jsonip.com from a PC, you get your router's address, not your PC's address.
See also: Finding local IP addresses using Python's stdlib
To make your program working, make it to accept connections on all interfaces. See the first example in the socket docs. On Linux, use port numbers >= 1024. Ports < 1024 are reserved, not available to regular users.
Final point is that a firewall may prevent connections to your server. It depends on your system and setup.
I need my own IP in a small script and in order not to hardcode it, I`ve found a piece of code from here(stackoverflow) that works.
This--
with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
s.connect(("8.8.8.8", 80))
print(s.getsockname()[0])
--
What is not clear for me is why it only works on UDP and not TCP? It has something to do with the google dns server? Thanks in advance.
This has nothing to do with Google and nothing to do with DNS.
All what this code does is to "connect" a UDP socket to an external IP, so that the OS kernel figures out which local IP address it needs to use in order to reach this external system. This is no real connection, i.e. there is no traffic involved but the OS kernel is only checking routing tables and local interfaces in order to decide which IP address to use as source in case one would actually use the socket to send data.
One could do the same with TCP. But in this case a real TCP connection would be established which means that actual traffic would be exchanged and that the connect would fail if the external system would not be reachable on this port (i.e. no listener, firewall in between etc).
With UDP instead connect will not produce any traffic and would fail only if no route to the destination IP address could be determined. This also means that an arbitrary external IP address and port could be used, i.e. ('1.1.1.1',11) would work the same as ('8.8.8.8',80).
I've been struggling with this for a few hours now and really just don't know where to go from here. I've got an arduino uno with a wifi shield connected to a network, and a laptop with Ubuntu connected to the same network. I'm using the arduino Wifi Library to connect to the network.
I can send data to my laptop from the arduino and print it successfully using: sudo nc -l 25565
I am also trying to use the following python code to do the same thing I did with nc which is also being run as sudo just in case:
#!/usr/bin/env python
import socket
TCP_IP = '127.0.0.1'
TCP_PORT = 25565
BUFFER_SIZE = 1024
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP,TCP_PORT))
s.listen(1)
(conn,addr) = s.accept()
print 'Connection address: ',addr
while True:
data = conn.recv(BUFFER_SIZE)
if not data: break
print 'received data: ',data
conn.send('ECHO')
conn.close()
s.close()
But it just hangs at (conn,addr) = s.accept(). Using a client python script on the same laptop I can connect to the above server and I can send data to it which the server then prints.
I just have no idea why nc will print from the arduino but the python server script won't, even though it will print from a python client. Could the arduino libraries be failing to follow some standard that python expects? Thanks in advance.
No, the arduino libraries are not "failing to follow some standard".
Your program is binding to the localhost interface, IP address 127.0.0.1. This means that only programs running on the same PC will be able to connect to your Python server.
Try this:
s.bind(('',TCP_PORT))
Reference:
https://docs.python.org/2/library/socket.html :
For IPv4 addresses, two special forms are accepted instead of a host address: the empty string represents INADDR_ANY, and the string '<broadcast>' represents INADDR_BROADCAST. The behavior is not available for IPv6 for backward compatibility, therefore, you may want to avoid these if you intend to support IPv6 with your Python programs.
https://docs.python.org/2/howto/sockets.html#creating-a-socket :
A couple things to notice: we used socket.gethostname() so that the socket would be visible to the outside world. If we had used s.bind(('localhost', 80)) or s.bind(('127.0.0.1', 80)) we would still have a “server” socket, but one that was only visible within the same machine. s.bind(('', 80)) specifies that the socket is reachable by any address the machine happens to have.
An eye-tracking application I use utilizes UDP to send packets of data. I made a python socket on the same computer to listen and dump the data into a .txt file. I already have this much working.
A separate application also written in python (what the eye-tracked subject is seeing) is running on a separate computer. Because the eye-tracking application is continuous and sends unnecessary data, so far I've had to manually parse out the instances when the subject is looking at desired stimuli. I did this based on a manually synchronized start of both the stimuli and eye-tracking applications and then digging through the log file.
What I want to do is have the second computer act as a second UDP client, sending a packet of data to the socket on the eye-tracking computer everytime the subject is looking at stimuli (where a marker is inserted into the .txt file previously mentioned). Is it possible to have a socket listening to two IP addresses at one time?
Here's my socket script:
#GT Pocket client program
import datetime
import socket
now = datetime.datetime.now()
filename = 'C:\gazelog_' + now.strftime("%Y_%m_%d_%H_%M") + '.txt'
UDP_IP = '127.0.0.1' # The remote host (in this case our local computer)
UDP_PORT = 6666 # The same port as used by the GT server by default
sock = socket.socket(socket.AF_INET, #internet
socket.SOCK_DGRAM) #UDP
sock.bind( (UDP_IP, UDP_PORT) )
while True:
data, addr = sock.recvfrom( 1024) #I assume buffer size is 1024 bytes.
print "Received Message:", data
with open(filename, "a") as myfile:
myfile.write(str(data + "\n"))
sock.close()
myfile.close()
EDIT:
#abarnert I was able to bind to the host address on the Ethernet interface and send a message from computer B to computer A, but computer A was no long able to receive packets from itself. When I specified UDP_IP = '0.0.0.0' computer B was no longer able to send data across the Ethernet. When I specified UDP_IP = '' I received the `error: [Errno 10048] Only one usage of each socket address (protocol/network address/port) is normally permitted
This have to do with the script I used on the Computer B to send the data:
import socket
UDP_IP = "169.254.35.231" # this was the host address I was able to send through.
UDP_PORT = 6666
MESSAGE = "Start"
print ("UDP target IP:"), UDP_IP
print ("UDP target port:"), UDP_PORT
print ("message:"), MESSAGE
sock = socket.socket(socket.AF_INET,
socket.SOCK_DGRAM)
sock.sendto(MESSAGE, (UDP_IP, UDP_PORT) )
I didn't know where (or if at all) I needed to specify INADDR_ANY, so I didn't. But I did try once where import socket.INADDR_ANY but got ImportError: No module named INADDR_ANY
Seems like a simple issue based on your response, so I'm not sure where I'm messing up.
EDIT2: I just reread your answer again and understand why socket.INADDR_ANY doesn't work. Please disregard that part of my previous edit
EDIT3: Okay so the reason that I wasn't picking up data when specifying the host IP was that the application I was collecting data from on Computer A was still specified to send to 127.0.0.1. So I figured it out. I am still curious why 0.0.0.0 didn't work though!
No. A socket can only be bound to a single address at a time.*
If there happens to be a single address that handles both things you want, you can use a single socket to listen to it. In this case, the INADDR_ANY host (0.0.0.0) may be exactly what you're looking for—that will handle any (IPv4) connections on all interfaces, both loopback and otherwise. And even if there is no pre-existing address that does what you want, you may be able to set one up via, e.g., an ipfilter-type interface.
But otherwise, you have to create two sockets. Which means you need to either multiplex with something like select, or create two threads.
In your case, you want to specify a host that can listen to both the local machine, and another machine on the same Ethernet network. You could get your host address on the Ethernet interface and bind that. (Your machine can talk to itself on any of its interfaces.) Usually, getting your address on "whatever interface is the default" works for this too—you'll see code that binds to socket.gethostname() in some places, like the Python Socket Programming HOWTO. But binding to INADDR_ANY is a lot simpler. Unless you want to make sure that machines on certain interfaces can't reach you (which is usually only a problem if you're, e.g., building a server intended to live on a firewall's DMZ), you'll usually want to use INADDR_ANY.
Finally, how do you bind to INADDR_ANY? The short answer is: just use UDP_IP = '', or UDP_IP = '0.0.0.0' if you want to be more explicit. Anyone who understands sockets, even if they don't know any Python, will understand what '0.0.0.0' means in server code.(You may wonder why Python doesn't have a constant for this in the socket module, especially when even lower-level languages like C do. The answer is that it does, but it's not really usable.**)
* Note that being bound to a single address doesn't mean you can only receive packets from a single address; it means you can receive packets from all networks where that single address is reachable. For example, if your machine has a LAN connection, where your address is 10.0.0.100, and a WAN connection, where your address is 8.9.10.11, if you bind 10.0.0.100, you can receive packets from other LAN clients like 10.0.0.201 and 10.0.0.202. But you can't receive packets from WAN clients like 9.10.11.12 as 10.0.0.100.
** In the low-level sockets API, dotted-string addresses like '0.0.0.0' are converted to 32-bit integers like 0. Python sometimes represents those integers as ints, and sometimes as 4-byte buffers like b'\0\0\0\0'. Depending on your platform and version, the socket.INADDR_ANY constant can be either 0 or b'\0\0\0\0'. The bind method will not take 0, and may not take b'\0\0\0\0'. And you can't convert to '0.0.0.0' without first checking which form you have, then calling the right functions on it. This is ugly. That's why it's easier to just use '0.0.0.0'.
I believe you can bind a raw socket to an entire interface, but you appear to be using two different interfaces.
It's probably best to use two sockets with select().
I am trying to make a simple server/client program pair.
On LAN they work fine, but when i try to connect from the "outside" it says connection refused. I shut down firewalls on both machines but i am still unable to connect, and i double checked the ip.
What am i doing wrong?
Thanks
Jake
Code:
import socket
host = ''
port = 9888
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((host,port))
s.listen(1)
conn, adrr = s.accept()
conn.send("Hello, world!")
s.close()
Client:
import socket
host = '68.x.x.x'
port = 9888
s = socket.socket(socket.AF_INET, socket_SOCK_STREAM)
s.connect((host,port))
print s.recv(200)
s.close()
You have one of two possible issues.
Erroneous network configuration
Bug(s) in code
The way to debug this is to try and rule one out. If we can get rid of the Code issue then we know it is a network issue.
Get a Socket Server and client that you know works and then try them as standalone programs. inside and outside of the firewall.
Go to this site and download the examples. Change the ports in both the client and the server, compile and run them. First on same machine within network, second from two machines on same network and then server from within and client from outside of network.
How's the argument you're passing to the .bind call for your server socket? That's the single likeliest cause -- e.g. if you're using 192.168.x.y for whatever values of x and y, or 10.x.y.z likewise, that's a local-network address only, not routed by inter-network routers by internet conventions (most routers can be programmed to forward some incoming packets to a specific local-network address, typically depending on ports, but that's very specific to router's brands and models).