Develop Reference

Python - A request to send or receive data was disallowed because the socket is not connected

I am creating a game in Pygame that requires a client-server part for the multiplayer.
First, I am checking if there are less than two connections. If this is the case, the client will be shown a screen that says 'waiting for connections'.
I have got the client to successfully send a '1' message to the server, which will respond with a '1' if the server is not full. Therefore, if the server does not respond with a 1, the server is full, and the client can continue.
However, I am getting this error mentioned in the title.
Server code:
import socket
import sys
import threading
from _thread import *
import time
s=socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host=socket.gethostname()
ip=socket.gethostbyname(host)
port=8000
connections=[]
print('Your local ip address is',ip)
s.bind((host,port))
s.listen(2)
def threaded_client(connection):
while True:
data=connection.recv(2048) #anything we receive
if not data:
break
connection.close()
def checkconnected(connections):
noofconn=len(connections)
while True:
print('Waiting for a connection...')
connection,address=s.accept()
print(address,'has connected to server hosted at port',address[1])
connections.append(address)
data=connection.recv(1024)
received=[]
counter=0
for letter in data:
received.append(data[counter])
counter+=1
received=(chr(received[0]))
if received=='1':#handling initial connections
if len(connections)!=2:
s.sendall(b'1')
if not data:
break
start_new_thread(threaded_client,(connection,))
s.close()
The client code that calls it:
host=socket.gethostname()
ip=socket.gethostbyname(host)
s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
address=address
port=8000
if address==ip:
ishost=True
else:
ishost=False
try:
s.connect((address,port))
connectionwaitingmenu()
connected=False
while connected==False:
s.sendall(b'1')
data=s.recv(1024)
received=[]
counter=0
for letter in data:
received.append(data[counter])
counter+=1
received=(chr(received[0]))
if received=='1':
connected=False
elif received!='1':
connected=True
classselection()
The error occurs on the s.sendall(b'1') line in the server code.

There are a few other problems in your code, but the cause of the error in the title is that you're using the wrong socket to send and receive data on the server side.
When a server accepts a new client (conn, addr = server.accept()) this returns a new socket, which represents the channel through which you communicate with the client. All further communication with this client happens by reading and writing on conn. You should not be calling recv() or sendall() on s, which is the server socket.
The code should look something like this:
# Assuming server is a bound/listening socket
conn, addr = server.accept()
# Send to client
conn.sendall(b'hello client')
# Receive from client
response = conn.recv(1024)
# NO
server.send(b'I am not connected')
this_wont_work = server.recv(1024)

UDP Server and Client Failing to Send And Recieve Messages

I am building a simple network chat in Python using UDP, however, when I run the server code on one machine and the client on another, no message is received by the server and no message is sent back to the client by the server script. Here is my code:
Server:
import socket, sys
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.bind(('', 9997)) #need higher port
while True:
x = raw_input("Enter your message: ")
sent = sock.sendto(x, ('', 9997))
data, address = sock.recvfrom(4096)
print data, " ", address
sock.close()
Client:
import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
while True:
print "Waiting to receive"
data, server = sock.recvfrom(4096)
print data
x = raw_input("Enter message: ")
sent = sock.sendto(x, server)
sock.close()
Does anyone know what I am doing wrong here? Is is possible that code is fine, but the UDP is not reliable enough and is dropping the message?

As I said, since your code seems a little unclear (to me, at least), I'm posting you a very similar working example.
Here's the Server:
import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
server_address = ('localhost', 1932)
sock.bind(server_address)
BUFFER_SIZE = 4096
try:
while True:
data, address = sock.recvfrom(BUFFER_SIZE)
print "Client sends: ", data
reply = raw_input("Your response:\n")
sock.sendto(reply,address)
except KeyboardInterrupt:
sock.close()
The server creates a socket and binds it to its address and the port it's listening to, 1932 in our case. He waits for an incoming message, asks for a reply, then sends it back to the sender.
Here's the Client:
import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
client_address = ('localhost', 1931)
server_address = ('localhost', 1932)
sock.bind(client_address)
BUFFER_SIZE = 4096
try:
first_msg = raw_input("Your first message:\n")
sock.sendto(first_msg,server_address)
while True:
data, address = sock.recvfrom(BUFFER_SIZE)
print "Client sends: ", data
reply = raw_input("Your response:\n")
sock.sendto(reply,address)
except KeyboardInterrupt:
sock.close()
It's very similar to the server, the only difference is that it sends a message before the while loop, in order to start the conversation. Then it just enters the receive/reply loop, just as the server does. It has the server address too, that is different (different port, since I'm on localhost)
The try/catch block is here just to close gracefully the whole process.
I used localhost and different ports on my computer and tested it, and it works. You should just change the addresses to get it working over LAN, and you could keep the same port if the addresses are different, it should work.

using select() method for client/ server chat in Python

I am writing a client/ server program in Python where, once the client and server have successfully connected via a socket, they may exchange messages. Below is my server and client code. When compiled, the connection is established correctly and the messages are sent successfully, but one cannot send a second message until it has received a response from the other party.
For example:
Client sends: "Hello, server!"
Server sends: "I have received your message, client!"
Client sends: "great, here's another one"
Client sends: "and a second one!"
At this point, the server terminal window has received the message saying "great, here's another one", but must first reply to this message before receiving "and a second one!".
I think my issue is that I need to use the select() method, but do not understand how to do so. How can I fix this?
#The server code
HOST = ''
PORT = 9999
s = socket(AF_INET, SOCK_STREAM)
s.bind((HOST, PORT))
print("Now listening...")
s.listen(1) #only needs to receive one connection (the client)
conn, addr = s.accept() #accepts the connection
print("Connected by: ", addr) #prints the connection
i = True
while i is True:
data = conn.recv(1024) #receives data
print('Received:' , repr(data)) #prints the message from client
reply = raw_input() #server types a response
conn.sendall(reply) #server now sends response back to client
close()
below is the client code (client.py)
The client code
from socket import*
HOST = '192.168.41.1'
PORT = 9999
s = socket(AF_INET, SOCK_STREAM)
s.connect((HOST, PORT))
while True:
message = raw_input() #client's message to the server
s.send(message) #sends message to the server
print("Waiting for response...")
reply = s.recv(1024) #receives message from server
print("New message: " + repr(reply)) #prints the message received
close()

Look at the following examples:
http://code.activestate.com/recipes/531824-chat-server-client-using-selectselect/
and
http://www.binarytides.com/code-chat-application-server-client-sockets-python/
also some similar answer here:
Python client side in chat
What you are missing is select on client side where its select if to handle input from server or from command line.
So in that case, you don't have to wait for server response and can send 2 calls one after another from the client.
Freely adapting the answers above to what you wished to accomplish.
(I didn't test it - so make sure to check it)
from socket import*
import sys
import select
HOST = '192.168.41.1'
PORT = 9999
s = socket(AF_INET, SOCK_STREAM)
s.connect((HOST, PORT))
while True:
socket_list = [sys.stdin, s]
# Get the list sockets which are readable
read_sockets, write_sockets, error_sockets = select.select(
socket_list, [], [])
for sock in read_sockets:
#incoming message from remote server
if sock == s:
data = sock.recv(1024)
if not data:
print('\nDisconnected from server')
break
else:
#print data
sys.stdout.write(data)
# prints the message received
print("New message: " + repr(data))
prompt()
#user entered a message
else:
msg = sys.stdin.readline()
s.send(msg)
prompt()
s.close()

I would strongly suggest reading and familiarizing with this document and especially the non-blocking sockets part.
Your code now blocks when waiting for the data to arrive from the user. You want to instruct your program to wait for the data from the socket and at the same time allow user to type input.

Python Socket errno 10054 only when client.py runs

There are some other posts about this issue but none did help me with mine.
I'm trying to build a total simple server - client relationship in python
server.py
#!/usr/bin/python
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(("127.0.0.1",8889))
s.listen(1)
try:
while True:
client, add = s.accept()
data = client.recv(1024)
if not data:
print 'No data'
print data
finally:
s.close()
client.py
#!/usr/bin/python
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("127.0.0.1",8889))
try:
while True:
message = 'Foo'
s.send(message)
ans = s.recv(1024)
print ans
finally:
s.close()
I start by running the server first, but when I try to run the client I'm getting this Errno 10054 --> An existing connection was forcibly closed by the remote host
While request the browser with the ip and the related port, I receive some data.
I'm quiet new to networking, so please explain what might be obvious wrong in my code.
EDIT* Main issue is, that the client is somehow wrong, because it returns also an empty string on recv
Thank you in advance

Main issue is, that the client is somehow wrong, because it returns also an empty string on recv
The client isn't receiving anything from the server because the server is not sending anything.
On the server side, after print data, adding client.send(data) will send the string back to the client.

I am guessing:
The server accepts one socket and then does
client, add = s.accept()
data = client.recv(1024)
...
client, add = s.accept()
The client does this in the mean time:
s.send(message)
ans = s.recv(1024) # blocks until timeout
If now an other client connects to the server then client is replaced, the socket garbage collected and closed. s.recv(1024) will then tell that the connection is reset.
Have a look at import select or twisted (google around) to handle multiple connections at once.

socket.send working only once in python code for an echo client

I have the following code for an echo client that sends data to an echo server using socket connection:
echo_client.py
import socket
host = '192.168.2.2'
port = 50000
size = 1024
def get_command():
#..Code for this here
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((host,port))
while 1:
msg = get_command()
if msg == 'turn on':
s.send('Y')
elif msg == 'turn off':
s.send('N')
elif msg == 'bye bye':
break
else:
s.send('X')
data = s.recv(size)
print 'Received: ',data
s.close()
echo_server.py
import socket
host = ''
port = 50000
backlog = 5
size = 1024
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((host,port))
s.listen(backlog)
while 1:
client, address = s.accept()
data = client.recv(size)
if data:
client.send(data)
client.close()
The problem im facing is that in the client s.send works only the first time even though its in an infinite loop. The client crashes with connection timed out, some time after the first send/receive has completed.
Why is s.send working only once ?. How can i fix this in my code ?
Please Help
Thank You

Your server code only calls recv once. You should call accept once if you only want to receive one connection, but then you need to loop calling recv and send.

Your problem is that you are blocking on the accept inside the server's loop.
This is expecting the server to accept connections from more than one client. If you want that, and for each client to send multiple commands, you would need to spawn a new thread (or process) after the accept, with a new while loop (for client communication) in that thread/process.
To fix your example to work with just one client, you need to move the accept outside the loop, like so:
client, address = s.accept()
while 1:
data = client.recv(size)
if data:
client.send(data)