I have the following client/server python code. The print line from the server where i used f-string interpolation does not show anything when the code is executed and I would like to know why?
I followed this tutorial and on their end the print line shows result.
tutorial: https://www.tutorialspoint.com/python/python_networking.htm
line: Got connection from ('127.0.0.1', 48437)
my server code:
#!/usr/bin/python
# Server.py
# Import socket module
import socket
# Create a socket object
s = socket.socket()
# Get local machine name
host = socket.gethostname()
# Reserve a port number for the socket service
port = 22226
# Bind the host address and the port number
s.bind((host, port))
# Listens for the client connections made for the socket.
# The argument shows maximum number of queued connections and it is 1 at minimum
s.listen(5)
while True:
# Establish connection with client.
c, addr = s.accept()
print(f"Got connection from {addr}")
c.send(b'Thank you for connecting')
c.close() # Close the connection
my client code:
#!/usr/bin/python
# client.py
# Import socket module
import socket
# Create a socket object
s = socket.socket()
# Get local machine name
host = socket.gethostname()
# Reserve a port number for the socket service
port = 22226
# Connect the host address and the port number
s.connect((host, port))
# Read at most 1024 bytes
print(s.recv(1024))
s.close() # Close the socket when done
I've recently been tinkering around with the python socket module and I have come across an issue.
Here is my python server side script (im using python3.8.2)
import socket
#defin socket object
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((socket.gethostname(), 0))
s.listen(5)
while True:
clientsocket, address = s.accept()
print(f"connection from client has been established")
clientsocket.send(bytes("welcome to the server!", "utf-8"))
My server side script runs fine, however when i run the client script
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((socket.gethostname(127.0.0.1), 0))
msg = s.recv(1024)
print(msg.decode("utf-8"))
i get the following:
File "client.py", line 3
s.connect((socket.gethostname(127.0.0.1), 0))
^
SyntaxError: invalid syntax
I've tried changing the IP to my computer host name and gives the following:
raceback (most recent call last):
File "client.py", line 3, in <module>
s.connect(socket.gethostname((LAPTOP-XXXXXXX), 0))
NameError: name 'LAPTOP' is not defined
There are multiple issues:
when specifying IP addresses and hostnames, they must be formatted as strings (e.g. "127.0.0.1" and "LAPTOP-XXXXXXX"). Specifying them without quotes causes Python to attempt to interpret them as other tokens, such as variable names, reserved keyword, numbers, etc., which fails causing erros such as SyntaxError and NameError.
socket.gethostname() does not take an argument
specifying port 0 in the socket.bind() call results in a random high numbered port being assigned, so you either need to hardcode the port you use or dynamically specify the correct port in your client (e.g. by specifying it as an argument when executing the program)
in the server code, socket.gethostname() may not end up using the loopback address. One option here is using an empty string, which results in accepting connections on any IPv4 address.
Here's a working implementation:
server.py
import socket
HOST = ''
PORT = 45555
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((HOST, PORT))
host_addr = s.getsockname()
print("listening on {}:{}".format(host_addr[0], host_addr[1]))
s.listen(5)
while True:
client_socket, client_addr = s.accept()
print("connection from {}:{} established".format(client_addr[0], client_addr[1]))
client_socket.send(bytes("welcome to the server!", "utf-8"))
client.py
import socket
HOST = '127.0.0.1'
PORT = 45555
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
msg = s.recv(1024)
print(msg.decode("utf-8"))
Output from the server:
$ python3 server.py
listening on 0.0.0.0:45555
connection from 127.0.0.1:51188 established
connection from 127.0.0.1:51244 established
Output from client:
$ python3 client.py
welcome to the server!
$ python3 client.py
welcome to the server!
Put the 127.0.0.1 as string in gethostname
In the /etc/hosts file content, You will have an IP address mapping with '127.0.1.1' to your hostname. This will cause the name resolution to get 127.0.1.1. Just comment this line. So Every one in your LAN can receive the data when they connect with your ip (192.168.1.*). Used threading to manage multiple Clients.
Here's the Server and Client Code:
Server Code:
import socket
import os
from threading import Thread
import threading
import time
import datetime
def listener(client, address):
print ("Accepted connection from: ", address)
with clients_lock:
clients.add(client)
try:
while True:
client.send(a)
time.sleep(2)
finally:
with clients_lock:
clients.remove(client)
client.close()
clients = set()
clients_lock = threading.Lock()
host = socket.getfqdn() # it gets ip of lan
port = 10016
s = socket.socket()
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((host,port))
s.listen(3)
th = []
print ("Server is listening for connections...")
while True:
client, address = s.accept()
timestamp = datetime.datetime.now().strftime("%b %d %Y,%a, %I:%M:%S %p")
a = ("Hi Steven!!!" + timestamp).encode()
th.append(Thread(target=listener, args = (client,address)).start())
s.close()
Client Code:
import socket
import os
import time
s = socket.socket()
host = '192.168.1.43' #my server ip
port = 10016
print(host)
print(port)
s.connect((host, port))
while True:
print((s.recv(1024)).decode())
s.close()
Output:
(base) paulsteven#smackcoders:~$ python server.py
Server is listening for connections...
Accepted connection from: ('192.168.1.43', 38716)
(base) paulsteven#smackcoders:~$ python client.py
192.168.1.43
10016
Hi Steven!!!Feb 19 2020,Wed, 11:13:17 AM
Hi Steven!!!Feb 19 2020,Wed, 11:13:17 AM
Hi Steven!!!Feb 19 2020,Wed, 11:13:17 AM
I've got a simple client and server I found on an online tutorial
#server.py
import socket # Import socket module
s = socket.socket() # Create a socket object
host = 'localhost' # Get local machine name
port = 12345 # Reserve a port for your service.
s.bind((host, port)) # Bind to the port
s.listen(5) # Now wait for client connection.
while True:
c, addr = s.accept() # Establish connection with client.
print 'Got connection from', addr
c.send('Thank you for connecting')
c.close() # Close the connection
#client # This is client.py file
import socket # Import socket module
s = socket.socket() # Create a socket object
host = 'localhost'
port = 12345 # Reserve a port for your service.
s.connect((host, port))
print s.recv(1024)
s.close # Close the socket when done
When I run my client.py all it does is print an empty string when it should print ('Thank you for connecting'). When I connect localhost 12345 from telnet it sends the message fine so I don't know why my client isn't receiving the message
Any thoughts. I'm very new to socket programming and would love to find a solution so I can move on.
While running your script as is, I got this error:
Waiting connections ...
Got connection from ('127.0.0.1', 63875)
Traceback (most recent call last):
File "serv.py", line 14, in <module>
c.send('Thank you for connecting')
TypeError: a bytes-like object is required, not 'str'
Few things here:
Ensure you're sending bytes instead of str. you could do this by replacing line 14 with:
c.send(b'Thank you for connecting')
Also, it's always useful to declare your sockets s like this:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
Further read:
Py2: https://docs.python.org/2/library/socket.html
Py3: https://docs.python.org/3/library/socket.html
Hope it works! :)
I'm trying to make simple Client-Server program but it's only working when I'm running both scripts on same computer, when moving it to other computer - It does not make connection at all.
Server:
__author__ = 'user-pc'
import socket # Import socket module
s = socket.socket() # Create a socket object
host="0.0.0.0" # Bind with everyone
port = 13254 # Reserve a port for your service.
s.bind((host, port)) # Bind to the port
s.listen(5) # Now wait for client connection.
while True:
c, addr = s.accept() # Establish connection with client.
print 'Got connection from', addr
c.send('Thank you for connecting')
c.close() # Close the connection
Client:
__author__ = 'user-pc'
import socket # Import socket module
s = socket.socket() # Create a socket object
host = "192.168.10.4" # Server Ip
port = 13254 # Reserve a port for your service.
s.connect((host, port))
print s.recv(1024)
s.close # Close the socket when done
Can you please help me to figure the problem?
Thanks.
As it works when you run both scripts on the server it is likely your port is closed.
Verify your port is open. Go to this website: http://www.canyouseeme.org/
Enter your port and IP. It is highly likely your port is closed. This will verify that. Assuming your port is open you need to look into your firewall settings as reccomended by dmg in the comment above. Then, it is no longer a python issue!
I learned sockets in python. When I tried to programming sockets script in one computer, it worked, but when I tried to programming sockets script with two different computers and open socket with connection, it didn't work.
One computer(the server):
import socket
s = socket.socket()
host = socket.gethostname()
port = 1234
s.bind((host, port))
s.listen(5)
while True:
c, addr = s.accept()
print 'Got connection from', addr
c.send('Thank you for connecting')
c.close()
Second computer(the client):
import socket
s = socket.socket()
host = raw_input("The ip you want to connect to: ")
port = 1234
s.connect((host, port))
print s.recv(1024)
Error:
socket.error: [Errno 10061]
What is the problem in the scripts? Why it doesn't work?
Errno 10061:
It means the server you are trying to connect to is not waiting for one.
Make sure you have the port number open.
Try killing all python processes and start server again.
Update
Instead of
host = socket.gethostname()
use
host = ""