How to check if a socket was closed on this end in Python
If by «this end» you meant server-side, this answer should help. If you meant client-side, the following code from this answer should work.
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How to know the if the socket connection is closed in python?
First, it is worth saying that in most situations it seems best to handle this in the main handler loop where you can simply test for EOF (empty string received by socket.recv() . However, I came across the need to test for this and the following seemed better than passing another callback in to the thread to get this state, etc)
The following is what I am using, but I am very new to this though, so please provide feedback if there is a better or more efficient way to do this and I’ll update this answer.
It seems like the best way to do this is to check getpeername() (testing socket.recv() here is bad since our test would alter the buffer, for example.)
Return the address of the remote endpoint. For IP sockets, the address info is a pair (hostaddr, port).
If this fails it raises a socket.error [Errno 9] Bad file descriptor.
def is_socket_valid(socket_instance): """ Return True if this socket is connected. """ if not socket_instance: return False try: socket_instance.getsockname() except socket.error as err: err_type = err.args[0] if err_type == errno.EBADF: # 9: Bad file descriptor return False try: socket_instance.getpeername() except socket.error as err: err_type = err.args[0] if err_type in [errno.EBADF, errno.ENOTCONN]: # 9: Bad file descriptor. return False # 107: Transport endpoint is not connected return True Note: I have the first if-check in there because I am testing an attribute that may be None as well.
- This isn’t as explicit as I’d like but in my tests it seems to be accurate.
- The original question mentions wanting to know the reason for not being connected. This doesn’t address that.
Additionally, another answer mentions fileno() returns a negative number if the local side of the socket is closed. I get the same error 9. Either way, this doesn’t test the other side in the case that this is valid.
>>> s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) >>> s.fileno() 10 >>> s.close() >>> s.fileno() --------------------------------------------------------------------------- error Traceback (most recent call last) ----> 1 s.fileno() /tools/package/python/2.7.13/lib/python2.7/socket.pyc in meth(name, self, *args) 226 227 def meth(name,self,*args): --> 228 return getattr(self._sock,name)(*args) 229 230 for _m in _socketmethods: /tools/package/python/2.7.13/lib/python2.7/socket.pyc in _dummy(*args) 172 __slots__ = [] 173 def _dummy(*args): --> 174 raise error(EBADF, 'Bad file descriptor') 175 # All _delegate_methods must also be initialized here. 176 send = recv = recv_into = sendto = recvfrom = recvfrom_into = _dummy error: [Errno 9] Bad file descriptor This will give a True/False answer.
Check if socket is closed python
Subreddit for posting questions and asking for general advice about your python code.
Hi so I have this Python socket chat program and how would I know when a client has disconnected?
What i have so far: I am running a daemon thread on each client connected to my server, it’s called «handle» because it’s handling each client/socket individually in a thread.
clients = [] #active clients nicknames = [] #active nicknames def handle(client): «»»This function will be run on every connected client, and will be recieving messages and broadcasting them to all clients connected.»»» while True: try: message = client.recv(1024).decode(‘utf-8’) print(f’Recieved ‘) broadcast(message) #for broadcasting to all clients connected the message except: print(‘something went wrong. ‘) tmp = client # A temp variable for refering to client after removal client.close() #close connection to client nickname = nicknames[clients.index(client)] clients.remove(client) #remove the client from active clients broadcast(f’ has left the chat!’) nicknames.remove(nickname) #remove the nickname from active nicknames break
So it will run in a daemon thread on every connected client/socket and will wait for a message to be recieved and then send the message to all other clients connected. The problem I am facing is that when ever a client disconnects it spams «recieved » in the console. So apparently the client sends empty bytes strings to the server after the client’s program have been terminated, but what I think should happen is that
message = client.recv(1024).decode(‘utf-8’) should raise an exception, and then trigger the exception block whenever a client disconnects, instead of recieving empty byte strings.
So my question is why is it not raising an exception and running the exception block?