When should I explicitly call 'close()' on a socket in Python? - sockets

I'm trying to write a very simple Python 2.7 function to listen for a socket connection on a localhost port.
Question is: If something bad happens when is my code responsible for killing the socket so that is not left dangling out there? In what cases will a socket error close the socket for me so that I don't need to call 'close()'?
I want to avoid having to start my testing all over with a different port because the old one was left open.
Python code sample:
def getconn(PORT,TIMEOUT_SECS):
conn = ''
try:
HOST = ''
s1 = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s1.settimeout(TIMEOUT_SECS)
s1.bind((HOST, PORT))
s1.listen(1)
conn, addr = s1.accept()
print('Connected by', addr)
except socket.timeout as e:
conn = 'socket timeout'
except socket.error as e:
conn = 'other socket error'
except:
conn = 'deaddead'
if s1:
s1.close()
return conn
And used here (say PORT argument is 19111)...
def runtest01_normalpoll(PORT):
conn = getconn(PORT, 10.0)
if conn == 'socket timeout' or conn == 'other socket error' or conn == 'deaddead':
print 'could not establish a connection...why you ask?', conn
else:
conn.close()
print 'done...'
It seems to work but am I missing any edge cases that would leave the socket open or cause anything else bad to happen?

Related

(Python)What do I do to stop receiving this error? [WinError 10013]An attempt was made to access a socket in a way forbidden by its access permissions

I'm trying to make a python socket client/server chat app, but can't seem to work around this error. I've used netstat -a|findstr 7000 to make sure the port was available, and it was. I don't have any antivirus running besides Windows Security. I also tried it after turning off all firewalls on my computer--have not messed with firewall settings in my router. I'm running both files in Anaconda Powershell Prompt as admin.
Any help is appreciated.
Code for server.py :
from socket import AF_INET, socket, SOCK_STREAM
import threading
BUFSIZ = 1024
FORMAT = 'utf-8'
SERVER = '192.168.1.10'
ADDR = (SERVER, 7000)
server = socket(AF_INET, SOCK_STREAM)
server.bind(ADDR)
sockets = {server}
clients = {}
def accept_incoming_connections():
while True:
client, client_addr = server.accept()
print ("%s:%s has connected." % client_addr)
client.send(bytes("Enter your name and press enter."), FORMAT)
sockets[client] = client_addr
# client_thread = threading.Thread(target=handle_client, args=(client,)).start()
def handle_client(client):
client_name = client.recv(BUFSIZ).decode(FORMAT)
client.send(bytes("Type .exit when you're ready to quit.", FORMAT))
msg = "%s has entered the chat." % client_name
broadcast(bytes(msg, FORMAT))
clients[client] = client_name
while True:
msg = client.recv(BUFSIZ)
if msg == bytes(".exit", FORMAT):
client.send(bytes(".exit", FORMAT))
client.close()
del clients[client]
broadcast(bytes("%s has left the chat." % client_name, FORMAT))
break
else:
broadcast(msg, client_name)
def broadcast(msg, name=""):
for client in clients:
client.send(bytes(name, FORMAT) + msg)
if __name__ == "__main__":
server.listen()
print("Awaiting connection.")
accept_incoming_connections()
Code for client.py :
import socket
import threading
BUFSIZ = 1024
FORMAT = 'utf-8'
SERVER = '192.168.1.10'
ADDR = (SERVER, 7000)
client_sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_sock.connect(ADDR)
def receive():
msg = client_sock.recv(BUFSIZ).decode(FORMAT)
print(msg)
def send():
msg = input('Enter msg: ')
msg.encode(FORMAT)
client_sock.send(msg)
if msg == ".exit":
client_sock.close()
receive_thread = Thread(target=receive)
receive_thread.start()
EDIT: I fixed it. I set SERVER to 'localhost' and PORT to 9999 for both server and client.

python 3.5.2 UdpServer sendto() error: module 'socket' has no attribute 'sendto'

I've problem with python socket at s.sendto(data,addr)
and my code like this
import socket
def Main():
host = '127.0.0.1'
port = 5000
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.bind((host, port))
print("server started")
while True:
data, addr = s.recvfrom(1024)
print ("message from : "+ str(addr))
print ("from connected user : "+ str(data))
data = str(data.upper())
print ("sending : "+ str(data))
socket.sendto(data, addr)
and result
socket.sendto(data, addr)
AttributeError: module 'socket' has no attribute 'sendto'
s.close()
if __name__ == '__main__':
Main()
and at UdpClient s.sendto is working
It seems that you mistyped the socket.sendto(... statement: The AttributeError is raised since the method sendto() is to be called from instances of the class socket.socket (as you have in s), and not from the socketmodule itself. See here for more details about the meaning of that statement.
So you basically need to change socket.sendto(... to s.sendto(...
also, if you want to check the attributes of any x object,(apart from reading the docs) you can simply check its x.__dict__ field, as explained here
cheers

Qpython, socket connection error

I'm learning server- and client-side connections:
What I'm attempting to do is connecting server- and client-side scripts with each other on Qpython(android)
The problem is when I run it, it gives me this:
"ConnectionRefusedError: Errno [111] Connection Refused"
When I run the same scripts on my computer it gives me no error.
Background information:
I'm using 2 different apps on my phone
And 1 on my computer.
But I suppose that can't be the problem
Client
import socket
import sys
HOST, PORT = "localhost", 9999
Data = " ".join(sys.argv[1:]) + input(" Enter Message:\n"
# Create a socket (SOCK_STREAM means a TCP socket)
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try:
# Connect to server and send data
sock.connect((HOST, PORT))
sock.sendall(bytes(data + "\n", "utf-8"))
# Receive data from the server and shut down
received = str(sock.recv(1024), "utf-8")
finally:
sock.close()
print("Sent: {}".format(data))
print("Received: {}".format(received))
Server
import socketserver
class MyTCPHandler(socketserver.BaseRequestHandler):
def handle(self):
# self.request is the TCP socket connected to the client
self.data = self.request.recv(1024).strip()
print("{} wrote:".format(self.client_address[0]))
print(self.data)
# just send back the same data, but upper-cased
self.request.sendall(self.data.upper())
if __name__ == "__main__":
HOST, PORT = "localhost", 9999
# Create the server, binding to localhost on port 9999
server = socketserver.TCPServer((HOST, PORT), MyTCPHandler)
server.serve_forever()

Socket Programming Python

import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('localhost', 8021))
s.listen(10)
while True:
conn, addr = s.accept()
print 'got connected from', addr
s.send("sending to client")
conn.close()
s.close()
The problem is as soon i run my client code, it shows "got connected from ('127.0.0.1', 52764)" but then it shows the error
Traceback (most recent call last):
File "D:\Python27\server", line 13, in <module>
s.send("sending to client")
error: [Errno 10057] A request to send or receive data was disallowed because the socket is not connected and (when sending on a datagram socket using a sendto call) no address was supplied
How can I correct it?
My client code is:
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
host = 'localhost'
port = 8021
s.connect((host, port))
revieved = s.recv(1024)
print "Recieved: ", recieved
Well, the answer is simple and I may snag some reputation here!
You are confusing your general socket with the specific client connection. What you receive from running s.accept() is a tuple which consists of: remote socket connection object and remote socket address. This way you can speak to specific client, by referring to the right connection object.
So the fixed could looks like this:
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('localhost', 8021))
s.listen(10)
while True:
conn, addr = s.accept()
print 'got connected from', addr
conn.send("sending to client")
conn.close()
s.close()
Assuming that everything else is working fine!

Python Socket Multiple Clients

So I am working on an iPhone app that requires a socket to handle multiple clients for online gaming. I have tried Twisted, and with much effort, I have failed to get a bunch of info to be sent at once, which is why I am now going to attempt socket.
My question is, using the code below, how would you be able to have multiple clients connected? I've tried lists, but I just can't figure out the format for that. How can this be accomplished where multiple clients are connected at once and I am able to send a message to a specific client?
Thank you!
#!/usr/bin/python # This is server.py file
import socket # Import socket module
s = socket.socket() # Create a socket object
host = socket.gethostname() # Get local machine name
port = 50000 # Reserve a port for your service.
print 'Server started!'
print 'Waiting for clients...'
s.bind((host, port)) # Bind to the port
s.listen(5) # Now wait for client connection.
c, addr = s.accept() # Establish connection with client.
print 'Got connection from', addr
while True:
msg = c.recv(1024)
print addr, ' >> ', msg
msg = raw_input('SERVER >> ')
c.send(msg);
#c.close() # Close the connection
Based on your question:
My question is, using the code below, how would you be able to have multiple clients connected? I've tried lists, but I just can't figure out the format for that. How can this be accomplished where multiple clients are connected at once and I am able to send a message to a specific client?
Using the code you gave, you can do this:
#!/usr/bin/python # This is server.py file
import socket # Import socket module
import thread
def on_new_client(clientsocket,addr):
while True:
msg = clientsocket.recv(1024)
#do some checks and if msg == someWeirdSignal: break:
print addr, ' >> ', msg
msg = raw_input('SERVER >> ')
#Maybe some code to compute the last digit of PI, play game or anything else can go here and when you are done.
clientsocket.send(msg)
clientsocket.close()
s = socket.socket() # Create a socket object
host = socket.gethostname() # Get local machine name
port = 50000 # Reserve a port for your service.
print 'Server started!'
print 'Waiting for clients...'
s.bind((host, port)) # Bind to the port
s.listen(5) # Now wait for client connection.
print 'Got connection from', addr
while True:
c, addr = s.accept() # Establish connection with client.
thread.start_new_thread(on_new_client,(c,addr))
#Note it's (addr,) not (addr) because second parameter is a tuple
#Edit: (c,addr)
#that's how you pass arguments to functions when creating new threads using thread module.
s.close()
As Eli Bendersky mentioned, you can use processes instead of threads, you can also check python threading module or other async sockets framework. Note: checks are left for you to implement how you want and this is just a basic framework.
accept can continuously provide new client connections. However, note that it, and other socket calls are usually blocking. Therefore you have a few options at this point:
Open new threads to handle clients, while the main thread goes back to accepting new clients
As above but with processes, instead of threads
Use asynchronous socket frameworks like Twisted, or a plethora of others
Here is the example from the SocketServer documentation which would make an excellent starting point
import SocketServer
class MyTCPHandler(SocketServer.BaseRequestHandler):
"""
The RequestHandler class for our server.
It is instantiated once per connection to the server, and must
override the handle() method to implement communication to the
client.
"""
def handle(self):
# self.request is the TCP socket connected to the client
self.data = self.request.recv(1024).strip()
print "{} wrote:".format(self.client_address[0])
print self.data
# just send back the same data, but upper-cased
self.request.sendall(self.data.upper())
if __name__ == "__main__":
HOST, PORT = "localhost", 9999
# Create the server, binding to localhost on port 9999
server = SocketServer.TCPServer((HOST, PORT), MyTCPHandler)
# Activate the server; this will keep running until you
# interrupt the program with Ctrl-C
server.serve_forever()
Try it from a terminal like this
$ telnet localhost 9999
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Hello
HELLOConnection closed by foreign host.
$ telnet localhost 9999
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Sausage
SAUSAGEConnection closed by foreign host.
You'll probably need to use A Forking or Threading Mixin too
This program will open 26 sockets where you would be able to connect a lot of TCP clients to it.
#!usr/bin/python
from thread import *
import socket
import sys
def clientthread(conn):
buffer=""
while True:
data = conn.recv(8192)
buffer+=data
print buffer
#conn.sendall(reply)
conn.close()
def main():
try:
host = '192.168.1.3'
port = 6666
tot_socket = 26
list_sock = []
for i in range(tot_socket):
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,1)
s.bind((host, port+i))
s.listen(10)
list_sock.append(s)
print "[*] Server listening on %s %d" %(host, (port+i))
while 1:
for j in range(len(list_sock)):
conn, addr = list_sock[j].accept()
print '[*] Connected with ' + addr[0] + ':' + str(addr[1])
start_new_thread(clientthread ,(conn,))
s.close()
except KeyboardInterrupt as msg:
sys.exit(0)
if __name__ == "__main__":
main()
def get_clients():
first_run = True
startMainMenu = False
while True:
if first_run:
global done
done = False
Thread(target=animate, args=("Waiting For Connection",)).start()
Client, address = objSocket.accept()
global menuIsOn
if menuIsOn:
menuIsOn = False # will stop main menu
startMainMenu = True
done = True
# Get Current Directory in Client Machine
current_client_directory = Client.recv(1024).decode("utf-8", errors="ignore")
# beep on connection
beep()
print(f"{bcolors.OKBLUE}\n***** Incoming Connection *****{bcolors.OKGREEN}")
print('* Connected to: ' + address[0] + ':' + str(address[1]))
try:
get_client_info(Client, first_run)
except Exception as e:
print("Error data received is not a json!")
print(e)
now = datetime.now()
current_time = now.strftime("%D %H:%M:%S")
print("* Current Time =", current_time)
print("* Current Folder in Client: " + current_client_directory + bcolors.WARNING)
connections.append(Client)
addresses.append(address)
if first_run:
Thread(target=threaded_main_menu, daemon=True).start()
first_run = False
else:
print(f"{bcolors.OKBLUE}* Hit Enter To Continue.{bcolors.WARNING}\n#>", end="")
if startMainMenu == True:
Thread(target=threaded_main_menu, daemon=True).start()
startMainMenu = False
#!/usr/bin/python
import sys
import os
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
port = 50000
try:
s.bind((socket.gethostname() , port))
except socket.error as msg:
print(str(msg))
s.listen(10)
conn, addr = s.accept()
print 'Got connection from'+addr[0]+':'+str(addr[1]))
while 1:
msg = s.recv(1024)
print +addr[0]+, ' >> ', msg
msg = raw_input('SERVER >>'),host
s.send(msg)
s.close()