Creating New Process For Each Request On Ssl Socket Gives "typeerror: Cannot Serialize Socket Object", But Doing Same With Normal/non Ssl Socket Works

I am trying to use keys and certificate generated using java keytool in python server and java client. I have created key & keystore, exported certificate, added certificate to

Solution 1:

I worked around this problem by accept the socket in the clear wrapping it with SSLContext within the child process. Everything I needed to create the SSLContext multiprocessing had no issues serializing.

UPDATE: The following is a server sudo code which illustrates the explanation above:

defclient_connection_handler(client_socket, client_address, ssl_settings):
    context = ssl.SSLContext()
    context.load_cert_chain(certfile=ssl_settings['certfile'], keyfile=ssl_settings['keyfile'],)
    context.verify_mode = ssl_settings["verify_mode"]
    context.load_verify_locations(cafile=ssl_settings["cafile"])
    client_secured_socket = context.wrap_socket(client_socket, server_side=True)
    ## send and receive data#
    client_secured_socket.close()


defserver():
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    server_socket.bind((hostname, port))
    server_socket.listen(5)
    whileTrue:
        # Waiting for client connection
        client_socket, client_address = server_socket.accept()
        concurrent_connections = len(multiprocessing.active_children())
        if max_concurrent_clients > concurrent_connections:
            p = multiprocessing.Process(target=client_connection_handler, args=(client_socket, client_address, ssl_settings))
            p.daemon = True
            p.start()
            continue# Max client connection has been reached
        client_socket.close()

Solution 2:

I dont know whether I understood the exact reason, but I am stating it here.

Looking at following stacktrace lines:

17        ForkingPickler(file, protocol).dump(obj)
18      File "D:\Programs\python\python-3.6.6-amd64\lib\socket.py", line 185, in __getstate__
19        raise TypeError("Cannot serialize socket object")
20TypeError: Cannot serialize socket object

it seems that multiprocessing module's Process.start() method serializes the parameters passed to it for passing them to new process. And it further seems that SSLSocket objects cannot be serialized. However, it seems that Socket objects can be serialized. This issue states the same and thats why the Socket based server works. However, I dont get why is this so (SSLSocket is not serializable but Socket objects can be serialized). I mean is there any method that is implemented by Socket objects which are not implemented by SSLSocket. Also note that the error occurs at socket.py, line 185, in __getstate__, that is in Socket class, but not in SSLSocket class.

I will like if someone confirms above reason (that is SSLSocket objects are not serializable and Socket objects are serializable), explains exactly why is this the case and provides solution for using SSLSocket with multiprocessing module.

Workaround

I ended up forking new process using os.fork. (Examples of os.fork can be found here). Its supported on linux only. So, I installed python on cygwin and then used it.