Python socket.recv exception

Question

I'm working on a very simple python socket server. I use non-blocking sockets. The server and client are running on windows 7 x64 with python 2.7.3. Here is the code where I receive data from the client :

def listenToSockets(self):
 while True:
 changed_sockets = self.currentSockets
 ready_to_read, ready_to_write, in_error = select.select(changed_sockets,[],[])
 for s in ready_to_read:
 # if its the server master socket someone is connecting
 if s == self.socket:
 (client_socket, address) = s.accept()
 print "putting " + address[0] + " onto connections\n";
 client_socket.setblocking(0)
 self.currentSockets.append(client_socket)
 print "current client count : " + str(len(self.currentSockets) - 1)
 else:
 data = ''
 try:
 while True:
 part = s.recv(4096)
 if part != '':
 data = data + part
 elif part == '':
 break
 except socket.error, (value,message): 
 print 'socket.error - ' + message
 if data != '':
 print "server received "+data
 else:
 print "Disconnected "+str(s.getsockname())
 self.currentSockets.remove(s)
 s.close()

And here is the client sending some data over and over again :

#client example
import socket
import time
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(('192.168.0.41', 9999))
while 1:
 client_socket.send("test")
 time.sleep(2) 

I see the server receiving the message "test" over and over again. But before it prints out what it received I get the following error message.

socket.error - A non-blocking socket operation could not be completed immediately.

Obviously an exception is thrown at part = s.recv(4096) but why?

Answer 1

That's precisely what a nonblocking socket is supposed to do.

• Read the available data, if any
• If nothing is available, raise an error rather than blocking

So you're getting an exception every time you try to receive and there's no data available.

• Barış Uşaklı: Found the error code on this link too. 10035 is not a fatal error and is throw when there is no data to receive. msdn.microsoft.com/en-ca/library/windows/desktop/…