Develop Reference

Can I make a client socket only to establish a connection using python 3.6

I'm reading about socket module in a web learning site about python, they gave us a simple steps to use socket module like follows:
import socket
with socket.socket() as client_socket:
hostname = '127.0.0.1'
port = 9090
address = (hostname, port)
client_socket.connect(address)
data = 'Wake up, Neo'
data = data.encode()
client_socket.send(data)
response = client_socket.recv(1024)
response = response.decode()
print(response)
when executing I got the error message:
ConnectionRefusedError: [WinError 10061] No connection could be made because the target machine actively refused it.
when I searched about this some sites was talking about server listening and I see in most of tutorials about server socket and they use it along with client one.
so Is the error message related to the fact that I'm not using a server socket and is it a must to use them both
Update:
after reading the answers I got, I went to the test.py file that the course instructors use to evaluate our codes and I see that they make the server socket in it , so the server is already made by them. that take me back to the Error I got why does it happen then.
def server(self):
'''function - creating a server and answering clients'''
self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self.sock.bind(('localhost', 9090))
self.ready = True
try:
self.sock.listen(1)
conn, addr = self.sock.accept()
self.connected = True
conn.settimeout(15)
while True:
data = conn.recv(1024)
self.message.append(data.decode('utf8'))
if len(self.message) > 1_000_000:
conn.send(
json.dumps({
'result': 'Too many attempts to connect!'
}).encode('utf8'))
break
if not data:
break

Each connection requires a client, which initiates the connection, and a server, which listens for the incoming connection from the client. The code you have shown is for the client end of the connection. In order for this to run successfully you will need a server listening for the connection you are trying to create.
In the code you showed us you have the lines
hostname = '127.0.0.1'
port = 9090
address = (hostname, port)
client_socket.connect(address)
These are the lines that define what server you are connecting to. In this case it is a server at 127.0.0.1 (which is localhost, the same machine you are running the code on) listening on port 9090.
If you want to make your own server then you can look at the documentation for Python sockets and the particular functions you want to know about are bind, listen, and accept. You can find examples at the bottom of that same page.
Given that you appear to have found this code as part of a course, I suspect they may provide you with matching server code at some point in order to be able to use this example.

Python | Connecting to a remote server using sockets

recently I've been messing around with sockets in python and i needed to connect to a remote server for a project. I know there are plenty of questions about this topic but none of the solutions worked for me and i am about to go mad if i can't get this to work.
Server code:
import socket
import threading
FORMAT = "UTF-8"
PORT = 55555
SERVER = ''
ADDR = ('0.0.0.0', PORT)
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(ADDR)
def handle_client(conn, addr):
print(f"[NEW CONNECTION] {addr} connected.")
conn.send("Test".encode(FORMAT))
def start():
server.listen()
print(f"[LISTENING] Server is listening on {PORT}")
while True:
connection, adress = server.accept()
thread = threading.Thread(target=handle_client, args=(connection, adress))
thread.start()
print(f"[ACTIVE CONNECTIONS] {threading.activeCount() - 1}")
print("[STARTING] server is starting...")
start()
Client Code:
import socket
import threading
FORMAT = "UTF-8"
PORT = 55555
SERVER = "xx.xxx.xxx.xxx" # public ip
print(f"\nconnecting... {PORT}\n")
ADDR = (SERVER, PORT)
client = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
client.connect(ADDR)
except:
print("Couldnt connect.")
print(client.recv(1024).decode(FORMAT))
When i change the SERVER variable in client script to my local ip (192.168.1.34), i can run these two scripts in two different pcs in the same LAN and it works well, i recieve the "Test" message in my client pc.
However, when i change the SERVER variable to my public ip and run the server in my server pc, i can't connect to the client pc. Here, my server and client pcs are NOT in the same network. Server is connected to my router whereas client is in another network. When i run the client script nothing happens and after a while i get [WINERROR 10057]
I've done port forwarding to port 55555. I tried disabling all firewalls and even creating a new rule in windows firewall to allow connections from port 55555. It still doesn't work and i can't figure out why.
If there is anyone who can see the problem here i would really appreciate it.

The only thing I can see that maybe is causing a problem is in your ADDR variable. I recently did a similar project that was successful, and in my sever code I did the equivalent of:
ADDR('',PORT)
I don't know for sure this would fix your problem, but it is my best guess from the info you provided.

Python client server

i've been trying to learn how to work with Telnet in python and I just got stuck on something.
importent to mention- I have no clue about anything in this subject. IP, telnet, sockets.. Nothing at all..
let's say this is my server:
import socket
import sys
HOST = ''
PORT = 8886
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
print 'Socket created'
try:
s.bind((HOST, PORT))
except socket.error , msg:
print 'Bind failed. Error Code : ' + str(msg[0]) + ' Message ' + msg[1]
sys.exit()
print 'Socket bind complete'
s.listen(10)
print 'Socket now listening'
conn, addr = s.accept()
print 'Connected with ' + addr[0] + ':' + str(addr[1])
print 'sending msg'
conn.sendall('My name is: ')
print 'msg sent'
data = conn.recv(1024)
print data
x="Hello %s and Thank you for your help! :)"%data
conn.sendall(x)
conn.close()
s.close()
Now this is just a basic thing for testing..
I was trying to create a client that wil connect to the server from a place far away, so I couldn't use localhost.
this is what i managed to do:
import socket
import sys
import time
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect(('85.65.110.8',8886))
data= sock.recv(1024)
lol=raw_input(data)
sock.sendall(lol)
data = sock.recv(1024)
print data
time.sleep(3)
sock.close()
the IP 85.65.110.8 is what i found from whatismyip.com- and it doesn't work even from my own computer.
I tried the IP 192.168.0.100 which works from the LAN but not from my friends house (who is testing it) and 'localhost' works aswell (still from me but not from my friend's house)
how can i change this so my friend could connect to the server?
thanks :)
(my Firewall is down and I port-forwarded.. I think... I hope so...)

If it works with the internal IP (192.168.x.x), but not with the external one (from whatsmyip, but remember it can change at any time without warning), then it is almost certainly a firewall or port-forwarding problem.
Unfortunately there's not enough information in your post to troubleshoot it (and firewalls go on SuperUser rather than StackOverflow in any case).

You probably have some router to connect to internet
so 85.65.110.8 is external address of this router.
On router you have to use port forwarding or virtual server
and set connection router 8886 <=> 192.168.0.100 8886
When someone will try to connect to 85.65.110.8 8886 then router will send this to 192.168.0.100 8886 and will send back all answers from 192.168.0.100 8886
If Internet Provider blocks some ports (for example 8886) then use 80.
It is web server port. (router 80 <=> 192.168.0.100 8886).
Then your friend will have to connect to 85.65.110.8 80 but your server will run on port 8886.
If Internet Provider changes your IP every day then you will need http://no-ip.com or http://dyndns.com .
Your friend can use telnet to test your port - or something more specialized like nmap or other port scanning tools

Why am I getting the error "connection refused" in Python? (Sockets)

I'm new to Sockets, please excuse my complete lack of understanding.
I have a server script(server.py):
#!/usr/bin/python
import socket #import the socket module
s = socket.socket() #Create a socket object
host = socket.gethostname() #Get the local machine name
port = 12397 # Reserve a port for your service
s.bind((host,port)) #Bind to the port
s.listen(5) #Wait for the client connection
while True:
c,addr = s.accept() #Establish a connection with the client
print "Got connection from", addr
c.send("Thank you for connecting!")
c.close()
and client script (client.py):
#!/usr/bin/python
import socket #import socket module
s = socket.socket() #create a socket object
host = '192.168.1.94' #Host i.p
port = 12397 #Reserve a port for your service
s.connect((host,port))
print s.recv(1024)
s.close
I go to my desktop terminal and start the script by typing:
python server.py
after which, I go to my laptop terminal and start the client script:
python client.py
but I get the following error:
File "client.py", line 9, in
s.connect((host,port))
File "/usr/lib/python2.7/socket.py", line 224, in meth
return getattr(self._sock,name)(*args)
socket.error: [Errno 111] Connection refused
I've tried using different port numbers to no avail. However, I was able to get the host name using the same ip and the gethostname() method in the client script and I can ping the desktop (server).

Instead of
host = socket.gethostname() #Get the local machine name
port = 12397 # Reserve a port for your service
s.bind((host,port)) #Bind to the port
you should try
port = 12397 # Reserve a port for your service
s.bind(('', port)) #Bind to the port
so that the listening socket isn't too restricted. Maybe otherwise the listening only occurs on one interface which, in turn, isn't related with the local network.
One example could be that it only listens to 127.0.0.1, which makes connecting from a different host impossible.

This error means that for whatever reason the client cannot connect to the port on the computer running server script. This can be caused by few things, like lack of routing to the destination, but since you can ping the server, it should not be the case. The other reason might be that you have a firewall somewhere between your client and the server - it could be on server itself or on the client. Given your network addressing, I assume both server and client are on the same LAN, so there shouldn't be any router/firewall involved that could block the traffic. In this case, I'd try the following:
check if you really have that port listening on the server (this should tell you if your code does what you think it should): based on your OS, but on linux you could do something like netstat -ntulp
check from the server, if you're accepting the connections to the server: again based on your OS, but telnet LISTENING_IP LISTENING_PORT should do the job
check if you can access the port of the server from the client, but not using the code: just us the telnet (or appropriate command for your OS) from the client
and then let us know the findings.

Assume s = socket.socket()
The server can be bound by following methods:
Method 1:
host = socket.gethostname()
s.bind((host, port))
Method 2:
host = socket.gethostbyname("localhost") #Note the extra letters "by"
s.bind((host, port))
Method 3:
host = socket.gethostbyname("192.168.1.48")
s.bind((host, port))
If you do not exactly use same method on the client side, you will get the error: socket.error errno 111 connection refused.
So, you have to use on the client side exactly same method to get the host, as you do on the server. For example, in case of client, you will correspondingly use following methods:
Method 1:
host = socket.gethostname()
s.connect((host, port))
Method 2:
host = socket.gethostbyname("localhost") # Get local machine name
s.connect((host, port))
Method 3:
host = socket.gethostbyname("192.168.1.48") # Get local machine name
s.connect((host, port))
Hope that resolves the problem.

host = socket.gethostname() # Get the local machine name
port = 12397 # Reserve a port for your service
s.bind((host,port)) # Bind to the port
I think this error may related to the DNS resolution.
This sentence host = socket.gethostname() get the host name, but if the operating system can not resolve the host name to local address, you would get the error.
Linux operating system can modify the /etc/hosts file, add one line in it. It looks like below( 'hostname' is which socket.gethostname() got).
127.0.0.1 hostname

in your server.py file make : host ='192.168.1.94' instead of host = socket.gethostname()

Pay attention to change the port number. Sometimes, you need just to change the port number. I experienced that when i made changes over changes over syntax and functions.

I was being able to ping my connection but was STILL getting the 'connection refused' error. Turns out I was pinging myself! That's what the problem was.

I was getting the same problem in my code, and after thow days of search i finally found the solution, and the problem is the function socket.gethostbyname(socket.gethostname) doesnt work in linux so instead of that you have to use socket.gethostbyname('put the hostname manually') not socket.gethostbyname('localhost'), use socket.gethostbyname('host') looking with ifconfig.

try this command in terminal:
sudo ufw enable
ufw allow 12397

Socket Server in Python

I am trying to set up a local server so that other PCs on the same local network can connect to it. When trying to do so, on the client side, I get the following error:
[Errno 10061] No connection could be made because the target machine actively refused it
I have been searching around for hours and still couldn't resolve this issue. I tried turning off my Firewall too, but nothing.
These are my server and client codes:
Server Code:
import socket
import threading
import SocketServer
import datetime
ver_codes = []
class ThreadedTCPRequestHandler(SocketServer.BaseRequestHandler):
def handle(self):
print threading.current_thread().isDaemon()
data = self.request.recv(1024)
command = data.split()[0]
if(command=="login"):
if(logged_in(data.split()[1])==False):
self.request.sendall(login(data.split()[1], data.split()[2]))
else:
self.request.sendall("already in")
class ThreadedTCPServer(SocketServer.ThreadingMixIn, SocketServer.TCPServer):
pass
def client(ip, port, message):
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((ip, port))
try:
sock.sendall(message)
response = sock.recv(1024)
print "Received: {}".format(response)
finally:
sock.close()
def logged_in(id_num):
for i in ver_codes:
if(i[0]==id_num):
return True
return False
def login(username, password):
login_file = open("Login.txt", "r")
match = login_file.readline()
while(match!="*"):
if(match.split()[0]==username):
if(match.split()[1]==password):
ver_codes.append([match.split()[0], encryption_code(match.split()[2])])
login_file.close()
return "{} {}".format(match.split()[2], encryption_code(match.split()[2]))
print "And Here"
match = login_file.readline()
return "Denied"
login_file.close()
def encryption_code(to_encrypt):
now = datetime.datetime.now()
return int(str(now.microsecond)) * int(to_encrypt)
if __name__ == "__main__":
HOST, PORT = "localhost", 7274
server = ThreadedTCPServer((HOST, PORT), ThreadedTCPRequestHandler)
ip, port = server.server_address
print server.server_address
server_thread = threading.Thread(target=server.serve_forever)
server_thread.daemon = False
server_thread.start()
print "Server loop running in thread:", server_thread.name
Client Code:
import socket
import sys
HOST, PORT = "localhost", 7274
data = " ".join(sys.argv[1:])
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
sock.connect((HOST, PORT))
sock.sendall("login mahdiNolan m1373")
received = sock.recv(1024)
finally:
sock.close()
I really appreciate any help you could give me!
Thanks A LOT beforehand!

Your issue is because you're listening on localhost - this will only accept connections from the local machine.
If you want to accept connections from anywhere, instead of "localhost" just pass the empty string "". This is equivalent to specifying INADDR_ANY to the C sockets API - see the ip man page for more information, or this page also looks like it has some useful explanation. In short, this means "accept connections on any local interface".
Instead of the empty string you can instead specify an IP address of a local interface to only accept connections on that interface - it's unlikely you need to do this unless you machine has multiple network cards inside it (e.g. acting as a gateway) and you only want to serve requests on one of the networks.
Also, on the client side you should use the actual address of the machine - replace "localhost" with the IP address or hostname of the server machine. For example, something like "192.168.0.99". If you want to find the IP address of the server under Windows, open a DOS window and run the ipconfig command, look for the line with IPv4 Address (assuming you've got an IPv4 network which is very likely).
The Windows firewall will also block the server from accepting connections as you've already found, but you shouldn't need to disable it - as soon as you run your server you should see a popup window where you can instruct it to accept connections (that was on Windows 7, it might be different on other versions). In any case, turning the software firewall off should allow everything to work, although whether that's a security risk is a matter outside of the scope of this question.