Python select.select() Examples

def interact(self):
        """
        Interact with the socket. This will send all keyboard input to the
        socket and input from the socket to the console until an EOF occurs.
        """

        sockets = [sys.stdin, self.channel]
        while True:
            ready = select.select(sockets, [], [])[0]

            if sys.stdin in ready:
                line = sys.stdin.readline().encode('latin1')
                if not line:
                    break
                self.write(line)

            if self.channel in ready:
                self.read(1, echo=True) 

def select_read(self, timeout=None):
        """
        Blocks until the socket is ready to be read from, or the timeout is hit

        :param timeout:
            A float - the period of time to wait for data to be read. None for
            no time limit.

        :return:
            A boolean - if data is ready to be read. Will only be False if
            timeout is not None.
        """

        # If we have buffered data, we consider a read possible
        if len(self._decrypted_bytes) > 0:
            return True

        read_ready, _, _ = select.select([self._socket], [], [], timeout)
        return len(read_ready) > 0 

def proxy(src, dst, callback=None):
    timeout = 10
    try:
        read_ready, _, _ = select.select([src], [], [], timeout)
        while len(read_ready):
            if callback:
                callback(src, dst)
            else:
                dst.send(src.recv(8192))
            read_ready, _, _ = select.select([src], [], [], timeout)
    except (socket.error, select.error, OSError, ValueError):
        pass
    try:
        src.shutdown(socket.SHUT_RDWR)
    except (socket.error, OSError, ValueError):
        pass
    src.close()
    try:
        dst.shutdown(socket.SHUT_RDWR)
    except (socket.error, OSError, ValueError):
        pass
    dst.close() 

def register_hstore_typecaster(conn):
    """
    Instead of using register_hstore() which converts hstore into a python
    dict, we query the 'oid' of hstore which will be different for each
    database and register a type caster that converts it to unicode.
    http://initd.org/psycopg/docs/extras.html#psycopg2.extras.register_hstore
    """
    with conn.cursor() as cur:
        try:
            cur.execute(
                "select t.oid FROM pg_type t WHERE t.typname = 'hstore' and t.typisdefined"
            )
            oid = cur.fetchone()[0]
            ext.register_type(ext.new_type((oid,), "HSTORE", ext.UNICODE))
        except Exception:
            pass 

def _doSSLHandshake(self) :
        count = 0
        while count < 10 :
            try :
                self._socket.do_handshake()
                break
            except ssl.SSLError as sslErr :
                count += 1
                if sslErr.args[0] == ssl.SSL_ERROR_WANT_READ :
                    select([self._socket], [], [], 1)
                elif sslErr.args[0] == ssl.SSL_ERROR_WANT_WRITE :
                    select([], [self._socket], [], 1)
                else :
                    raise XAsyncTCPClientException('SSL : Bad handshake : %s' % sslErr)
            except Exception as ex :
                raise XAsyncTCPClientException('SSL : Handshake error : %s' % ex)

    # ------------------------------------------------------------------------ 

def serve_forever(self, poll_interval=0.5):
        """Handle one request at a time until shutdown.

        Polls for shutdown every poll_interval seconds. Ignores
        self.timeout. If you need to do periodic tasks, do them in
        another thread.
        """
        self.__is_shut_down.clear()
        try:
            while not self.__shutdown_request:
                # XXX: Consider using another file descriptor or
                # connecting to the socket to wake this up instead of
                # polling. Polling reduces our responsiveness to a
                # shutdown request and wastes cpu at all other times.
                r, w, e = _eintr_retry(select.select, [self], [], [],
                                       poll_interval)
                if self in r:
                    self._handle_request_noblock()

                self.service_actions()
        finally:
            self.__shutdown_request = False
            self.__is_shut_down.set() 

def service_actions(self):
        """Called by the serve_forever() loop.

        May be overridden by a subclass / Mixin to implement any code that
        needs to be run during the loop.
        """
        pass

    # The distinction between handling, getting, processing and
    # finishing a request is fairly arbitrary.  Remember:
    #
    # - handle_request() is the top-level call.  It calls
    #   select, get_request(), verify_request() and process_request()
    # - get_request() is different for stream or datagram sockets
    # - process_request() is the place that may fork a new process
    #   or create a new thread to finish the request
    # - finish_request() instantiates the request handler class;
    #   this constructor will handle the request all by itself 

def handle_request(self):
        """Handle one request, possibly blocking.

        Respects self.timeout.
        """
        # Support people who used socket.settimeout() to escape
        # handle_request before self.timeout was available.
        timeout = self.socket.gettimeout()
        if timeout is None:
            timeout = self.timeout
        elif self.timeout is not None:
            timeout = min(timeout, self.timeout)
        fd_sets = _eintr_retry(select.select, [self], [], [], timeout)
        if not fd_sets[0]:
            self.handle_timeout()
            return
        self._handle_request_noblock() 

def _handle_request_noblock(self):
        """Handle one request, without blocking.

        I assume that select.select has returned that the socket is
        readable before this function was called, so there should be
        no risk of blocking in get_request().
        """
        try:
            request, client_address = self.get_request()
        except socket.error:
            return
        if self.verify_request(request, client_address):
            try:
                self.process_request(request, client_address)
            except:
                self.handle_error(request, client_address)
                self.shutdown_request(request) 

def select_wait_for_socket(sock, read=False, write=False, timeout=None):
    if not read and not write:
        raise RuntimeError("must specify at least one of read=True, write=True")
    rcheck = []
    wcheck = []
    if read:
        rcheck.append(sock)
    if write:
        wcheck.append(sock)
    # When doing a non-blocking connect, most systems signal success by
    # marking the socket writable. Windows, though, signals success by marked
    # it as "exceptional". We paper over the difference by checking the write
    # sockets for both conditions. (The stdlib selectors module does the same
    # thing.)
    fn = partial(select.select, rcheck, wcheck, wcheck)
    rready, wready, xready = _retry_on_intr(fn, timeout)
    return bool(rready or wready or xready) 

def poll_wait_for_socket(sock, read=False, write=False, timeout=None):
    if not read and not write:
        raise RuntimeError("must specify at least one of read=True, write=True")
    mask = 0
    if read:
        mask |= select.POLLIN
    if write:
        mask |= select.POLLOUT
    poll_obj = select.poll()
    poll_obj.register(sock, mask)

    # For some reason, poll() takes timeout in milliseconds
    def do_poll(t):
        if t is not None:
            t *= 1000
        return poll_obj.poll(t)

    return bool(_retry_on_intr(do_poll, timeout)) 

def _read_messages(self):
        while self.connected:
            try:
                r, w, e = select.select([self.sock], [], [])
            except select.error:
                break

            if r and self.connected:
                with self.cLock:
                    data = self.recv()
                    message = json.loads(data)

                    # If id is present -> notifies main thread to return this message as a reply
                    # Otherwise puts message into events queue so it will be dispatched as event
                    if 'id' in message:
                        self.replies[message['id']] = message
                        self.cLock.notify()
                    else:
                        self.events.put(message) 

def select_wait_for_socket(sock, read=False, write=False, timeout=None):
    if not read and not write:
        raise RuntimeError("must specify at least one of read=True, write=True")
    rcheck = []
    wcheck = []
    if read:
        rcheck.append(sock)
    if write:
        wcheck.append(sock)
    # When doing a non-blocking connect, most systems signal success by
    # marking the socket writable. Windows, though, signals success by marked
    # it as "exceptional". We paper over the difference by checking the write
    # sockets for both conditions. (The stdlib selectors module does the same
    # thing.)
    fn = partial(select.select, rcheck, wcheck, wcheck)
    rready, wready, xready = _retry_on_intr(fn, timeout)
    return bool(rready or wready or xready) 

def _retry_on_intr(fn, timeout):
        if timeout is None:
            deadline = float("inf")
        else:
            deadline = monotonic() + timeout

        while True:
            try:
                return fn(timeout)
            # OSError for 3 <= pyver < 3.5, select.error for pyver <= 2.7
            except (OSError, select.error) as e:
                # 'e.args[0]' incantation works for both OSError and select.error
                if e.args[0] != errno.EINTR:
                    raise
                else:
                    timeout = deadline - monotonic()
                    if timeout < 0:
                        timeout = 0
                    if timeout == float("inf"):
                        timeout = None
                    continue 

def _read_write(self, soc, max_idling=20):
        iw = [self.connection, soc]
        ow = []
        count = 0
        while 1:
            count += 1
            (ins, _, exs) = select.select(iw, ow, iw, 3)
            if exs:
                break
            if ins:
                for i in ins:
                    if i is soc:
                        out = self.connection
                    else:
                        out = soc
                    data = i.recv(8192)
                    if data:
                        out.send(data)
                        count = 0
            else:
                logging.warning("Idle")
            if count == max_idling:
                break 

def recv(self, *args, **kwargs):
        try:
            data = self.connection.recv(*args, **kwargs)
        except OpenSSL.SSL.SysCallError as e:
            if self.suppress_ragged_eofs and e.args == (-1, 'Unexpected EOF'):
                return b''
            else:
                raise
        except OpenSSL.SSL.ZeroReturnError as e:
            if self.connection.get_shutdown() == OpenSSL.SSL.RECEIVED_SHUTDOWN:
                return b''
            else:
                raise
        except OpenSSL.SSL.WantReadError:
            rd, wd, ed = select.select(
                [self.socket], [], [], self.socket.gettimeout())
            if not rd:
                raise timeout('The read operation timed out')
            else:
                return self.recv(*args, **kwargs)
        else:
            return data 

def _retry_on_intr(fn, timeout):
        if timeout is None:
            deadline = float("inf")
        else:
            deadline = monotonic() + timeout

        while True:
            try:
                return fn(timeout)
            # OSError for 3 <= pyver < 3.5, select.error for pyver <= 2.7
            except (OSError, select.error) as e:
                # 'e.args[0]' incantation works for both OSError and select.error
                if e.args[0] != errno.EINTR:
                    raise
                else:
                    timeout = deadline - monotonic()
                    if timeout < 0:
                        timeout = 0
                    if timeout == float("inf"):
                        timeout = None
                    continue 

def select_wait_for_socket(sock, read=False, write=False, timeout=None):
    if not read and not write:
        raise RuntimeError("must specify at least one of read=True, write=True")
    rcheck = []
    wcheck = []
    if read:
        rcheck.append(sock)
    if write:
        wcheck.append(sock)
    # When doing a non-blocking connect, most systems signal success by
    # marking the socket writable. Windows, though, signals success by marked
    # it as "exceptional". We paper over the difference by checking the write
    # sockets for both conditions. (The stdlib selectors module does the same
    # thing.)
    fn = partial(select.select, rcheck, wcheck, wcheck)
    rready, wready, xready = _retry_on_intr(fn, timeout)
    return bool(rready or wready or xready) 

def poll_wait_for_socket(sock, read=False, write=False, timeout=None):
    if not read and not write:
        raise RuntimeError("must specify at least one of read=True, write=True")
    mask = 0
    if read:
        mask |= select.POLLIN
    if write:
        mask |= select.POLLOUT
    poll_obj = select.poll()
    poll_obj.register(sock, mask)

    # For some reason, poll() takes timeout in milliseconds
    def do_poll(t):
        if t is not None:
            t *= 1000
        return poll_obj.poll(t)

    return bool(_retry_on_intr(do_poll, timeout)) 

def do_relay_udp(relay_sock, server, cfg):

	client = None

	while True:

		receiving, _, _ = select([relay_sock], [], [])

		if relay_sock in receiving:

			data, addr = relay_sock.recvfrom(BUFSIZE)

			if addr == server:
				data = proxify(data, cfg, client, server, to_server=False)
				relay_sock.sendto(data, client)

			else:
				client = addr
				data = proxify(data, cfg, client, server, to_server=True)
				relay_sock.sendto(data, server) 

def service_actions(self):
        """Called by the serve_forever() loop.

        May be overridden by a subclass / Mixin to implement any code that
        needs to be run during the loop.
        """
        pass

    # The distinction between handling, getting, processing and
    # finishing a request is fairly arbitrary.  Remember:
    #
    # - handle_request() is the top-level call.  It calls
    #   select, get_request(), verify_request() and process_request()
    # - get_request() is different for stream or datagram sockets
    # - process_request() is the place that may fork a new process
    #   or create a new thread to finish the request
    # - finish_request() instantiates the request handler class;
    #   this constructor will handle the request all by itself 

def ask_password(profile, interactive):
    """
    Prompt for profile password
    """
    if not PY3:
        profile = profile.encode(SYS_ENCODING)

    passmsg = "\nMaster Password for profile {0}: ".format(profile)

    if sys.stdin.isatty() and interactive:
        passwd = getpass(passmsg)

    else:
        # Ability to read the password from stdin (echo "pass" | ./firefox_...)
        if sys.stdin in select.select([sys.stdin], [], [], 0)[0]:
            passwd = sys.stdin.readline().rstrip("\n")
        else:
            LOG.warning("Master Password not provided, continuing with blank password")
            passwd = ""

    return py2_decode(passwd) 

def serve_forever(self, poll_interval=0.5):
        """Handle one request at a time until shutdown.

        Polls for shutdown every poll_interval seconds. Ignores
        self.timeout. If you need to do periodic tasks, do them in
        another thread.
        """
        self.__is_shut_down.clear()
        try:
            while not self.__shutdown_request:
                # XXX: Consider using another file descriptor or
                # connecting to the socket to wake this up instead of
                # polling. Polling reduces our responsiveness to a
                # shutdown request and wastes cpu at all other times.
                r, w, e = _eintr_retry(select.select, [self], [], [],
                                       poll_interval)
                if self in r:
                    self._handle_request_noblock()

                self.service_actions()
        finally:
            self.__shutdown_request = False
            self.__is_shut_down.set() 

def service_actions(self):
        """Called by the serve_forever() loop.

        May be overridden by a subclass / Mixin to implement any code that
        needs to be run during the loop.
        """
        pass

    # The distinction between handling, getting, processing and
    # finishing a request is fairly arbitrary.  Remember:
    #
    # - handle_request() is the top-level call.  It calls
    #   select, get_request(), verify_request() and process_request()
    # - get_request() is different for stream or datagram sockets
    # - process_request() is the place that may fork a new process
    #   or create a new thread to finish the request
    # - finish_request() instantiates the request handler class;
    #   this constructor will handle the request all by itself 

def handle_request(self):
        """Handle one request, possibly blocking.

        Respects self.timeout.
        """
        # Support people who used socket.settimeout() to escape
        # handle_request before self.timeout was available.
        timeout = self.socket.gettimeout()
        if timeout is None:
            timeout = self.timeout
        elif self.timeout is not None:
            timeout = min(timeout, self.timeout)
        fd_sets = _eintr_retry(select.select, [self], [], [], timeout)
        if not fd_sets[0]:
            self.handle_timeout()
            return
        self._handle_request_noblock() 

def _handle_request_noblock(self):
        """Handle one request, without blocking.

        I assume that select.select has returned that the socket is
        readable before this function was called, so there should be
        no risk of blocking in get_request().
        """
        try:
            request, client_address = self.get_request()
        except socket.error:
            return
        if self.verify_request(request, client_address):
            try:
                self.process_request(request, client_address)
            except:
                self.handle_error(request, client_address)
                self.shutdown_request(request) 

def next(self, timeout=0):
        """Return empty unless new data is ready for the client.
        Arguments:
            timeout: Default timeout=0  range zero to float specifies a time-out as a floating point
        number in seconds.  Will sit and wait for timeout seconds.  When the timeout argument is omitted
        the function blocks until at least one file descriptor is ready. A time-out value of zero specifies
        a poll and never blocks.
        """
        try:
            waitin, _waitout, _waiterror = select.select((self.streamSock,), (), (), timeout)
            if not waitin: return
            else:
                gpsd_response = self.streamSock.makefile()  # '.makefile(buffering=4096)' In strictly Python3
                self.response = gpsd_response.readline()
            return self.response

        except StopIteration as error:
            sys.stderr.write('The readline exception in GPSDSocket.next is--> {}'.format(error)) 

def next(self, timeout=0):
        """Return empty unless new data is ready for the client.
        Arguments:
            timeout: Default timeout=0  range zero to float specifies a time-out as a floating point
        number in seconds.  Will sit and wait for timeout seconds.  When the timeout argument is omitted
        the function blocks until at least one file descriptor is ready. A time-out value of zero specifies
        a poll and never blocks.
        """
        try:
            waitin, _waitout, _waiterror = select.select((self.streamSock,), (), (), timeout)
            if not waitin: return
            else:
                gpsd_response = self.streamSock.makefile()  # '.makefile(buffering=4096)' In strictly Python3
                self.response = gpsd_response.readline()
            return self.response

        except StopIteration as error:
            sys.stderr.write('The readline exception in GPSDSocket.next is--> {}'.format(error)) 

def handle_request(self):
        """Handle one request, possibly blocking.

        Respects self.timeout.
        """
        # Support people who used socket.settimeout() to escape
        # handle_request before self.timeout was available.
        timeout = self.socket.gettimeout()
        if timeout is None:
            timeout = self.timeout
        elif self.timeout is not None:
            timeout = min(timeout, self.timeout)
        fd_sets = _eintr_retry(select.select, [self], [], [], timeout)
        if not fd_sets[0]:
            self.handle_timeout()
            return
        self._handle_request_noblock() 

def _handle_request_noblock(self):
        """Handle one request, without blocking.

        I assume that select.select has returned that the socket is
        readable before this function was called, so there should be
        no risk of blocking in get_request().
        """
        try:
            request, client_address = self.get_request()
        except socket.error:
            return
        if self.verify_request(request, client_address):
            try:
                self.process_request(request, client_address)
            except:
                self.handle_error(request, client_address)
                self.shutdown_request(request)