python connect to server on same network

Question

I have got a server.py and a client.py.

If i run them on the same computer using the same port and host as 127.0.0.1 it works fine.

I got another laptop connected to the same network. I got my local ip address 129.94.209.9 and used that for the server. On the other laptop I tried connecting to the server but I couldn't.

Is this an issue with my code, with the network or I'm just using the wrong ip address?

Server.py

HOST = '129.94.209.9' 
PORT = 9999
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)
sockfd, addr = server_socket.accept()
send and receive messages etc....

Client.py

HOST = '129.94.209.9'
PORT = 9999
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
 sock.connect((HOST, PORT))
except:
 print("Cannot connect to the server")
send and receive messages etc...

Client prints "Cannot connect to the server"

Thanks!!

UPDATES: thanks for the comments

1) I did do sockfd, addr = server_socket.accept() sorry I forgot to add it, it was a few lines further down in the code.

2) The error is: [Errno 11] Resource temporarily unavailable

3) Ping does work

EDIT: It is working now when I plug both computers in by ethernet cable to the same network. Not sure why my the won't work when they are right next to each other connected to wifi. Thanks for all the suggestions! I'll investigate the network issue myself

• Klaus D.: At first you should remove the try / except or re-raise the exceptin to see the actual error message.
• Kind Stranger: Have you tried changing your except: to something like except Exception as ex:. This will allow you to see a better description of the exception with print(ex) and may provide a more information
• user6165050: Does ping from one machine to another works ?
• Friedpanseller: Yep I tried those, updated the question
• gbromios: what happens if you use HOST = '0.0.0.0' in the server.py?

Answer 1

Using the following code (my IP address rather than yours, of course) I see the expected behaviour.

so8srv.py:

import socket
HOST = '192.168.33.64' 
PORT = 9999
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)
print("Listening")
s = server_socket.accept()
print("Connected")

so8cli.py:

import socket
HOST = '192.168.33.64'
PORT = 9999
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
 sock.connect((HOST, PORT))
except Exception as e:
 print("Cannot connect to the server:", e)
print("Connected")

When I run it, the server prints "Listening". When I then run the client, both it and the server print "Connected".

You will notice that, unlike your code, my client doesn't just print hte same diagnostic for any exception that's raised, but instead reports the exception. As a matter of sound practice you should avoid bare except clauses, since your program will then take the same action whether the exception is caused by a programming error or a user action such as KeyboardInterrupt.

• Friedpanseller: Thanks. Looks like our code was all good but my wireless access point or router must have been doing some bad things. It's working now when I connect the laptops using ethernet cable rather than WiFi

Answer 2

Also try using this construction to obtain the IP address:

HOST=socket.gethostbyname(socket.gethostname())

• holdenweb: That can often end up returning the localhost address
• user6165050: Pay attention with this. On one machine you should have gethostbyname() and on another "0.0.0.0". Otherwise the connection between the two will fail
• holdenweb: That's not true, and sounds like cargo cult information. '0.0.0.0' is used on server sockets to listen on all available interfaces. It's perfectly valid to only listen on one interface, nominated by its IP address. There's absolutely no need to use hostnames at all - they are merely a convenience for human users.