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Artem30801 2902db9f14 docs: updated API docs for client_core and messaging

2020-10-20 01:11:58 +03:00

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Module lib.messaging

messaging is an universal for server and clients module (running both on Python 2.7 and 3.6+). This module contains utility functions and classes implementing high level protocol for TCP socket communication.

Module functions

get_ip_address

def get_ip_address()

Returns the IP address of current computer or localhost if no network connection present.

Returns:

string: IP address of current computer or `localhost` if no network connection present

message_callback

def message_callback(action_string)

In order to register your function as callback for message or command, you can use those decorators:

Callback decorator. Functions registered by this decorator will be called upon receiving action message.

Args:

action_string (str): Functions registered by this decorator will be called upon receiving action message with `action_string` as action.

Example:


@messaging.message_callback("test_command")

def test_command(client, *args, **kwargs):

    print(client, args, kwargs)

First argument passed to decorated function is instance of ConnectionManager, representing connection by which the message was received. Arguments and keyword arguments from message will also be passed.

request_callback

def request_callback(string_command)

In order to register your function as callback for message or command, you can use those decorators:

Callback decorator. Functions registered by this decorator will be called upon receiving request message.

Args:

string_command (str): Functions registered by this decorator will be called upon receiving request message with `string_command` as requested value.

Example:


@messaging.request_callback("time")

def test_respose(client, *args, **kwargs):

    return time.time()

First argument passed to decorated function is an instance of ConnectionManager, representing connection by which the message was received. Arguments and keyword arguments from message will also be passed. Functions registered by this decorator must return requested value or raise an exception. Returned value will be sent back.

set_keepalive

def set_keepalive(sock, after_idle_sec=1, interval_sec=3, max_fails=5)

Sets keepalive parameters of given socket.

Args:

sock (socket): Socket which parameters will be changed.

after_idle_sec (int, optional): Start sending keepalive packets after this amount of seconds. Defaults to 1.

interval_sec (int, optional): Interval of keepalive packets in seconds. Defaults to 3.

max_fails (int, optional): Count of fails leading to socket disconnect. Defaults to 5.

Raises:

NotImplementedError: for unknown platform.

Class ConnectionManager

This class represents high-level protocol of TCP connection.

Attributes:

selector (selector): Related selector object.

socket (socket): Socket object of the connection.

addr (str): Address of the peer.

buffer_size (int): Size of the sending/receiving buffer.

resume_queue (bool): Whether to resume sending queue upon peer reconnection.

resend_requests (bool): Whether to resend unanswered requests in queue to reconnected client.

init

def __init__(self, whoami='computer')

Args:

whoami (str, optional): What type of system the ConnectionManager is running on (`computer` or `pi`). Defaults to "computer".

Example:


connection = ConnectionManager(whoami)

connection.connect(client_selector, client_socket, client_addr)

close

def close(self)

Closes connection with the peer.

connect

def connect(self, client_selector, client_socket, client_addr)

[summary]

Args:

client_selector (selector): Related selector object.

client_socket (socket): Socket object of the connection.

client_addr (str): Address of the peer.

get_file

def get_file(self, client_filepath, filepath=None, callback=None, callback_args=(), callback_kwargs=None)

Requests file from peer located at client_filepath. Received file will be written to the filepath if specified.

Args:

client_filepath (str): Path to file to retrieve from peer.

filepath (str, optional): Path to write file upon receiving. If `None` - file will not be written. Defaults to None.

callback (function): Callable object (function, binded method, etc.) that would be called upon receiving response to this request or None.

callback_args (tuple, optional): Arguments for the callback. Defaults to ().

callback_kwargs (dict, optional): Keyword arguments for the callback. Defaults to None.

get_response

def get_response(self, requested_value, callback, request_args=(), request_kwargs=None, callback_args=(), callback_kwargs=None)

Sends request to the client and adds it to the request queue. The callback will be called upon receiving the response (see example below).

Args:

requested_value (string): Name of requested value.

callback (function): Callable object (function, binded method, etc.) that would be called upon receiving response to this request or None.

request_args (tuple, optional): Arguments for the request. Defaults to ().

request_kwargs (dict, optional): Keyword arguments for the request. Defaults to None.

callback_args (tuple, optional): Arguments for the callback. Defaults to ().

callback_kwargs (dict, optional): Keyword arguments for the callback. Defaults to None.

Example of a callback:


def callback(client, value, *args, **kwargs):

print(value, args, kwargs)

First argument passed to callback function is an instance of ConnectionManager, representing connection by which the message was received.

Second arguments is received value. Arguments and keyword arguments from response will also be passed.

process_events

def process_events(self, mask)

Processes read\write events with given mask.

Args:

mask (bytes): mask of the selector events.

process_received

def process_received(self, message)

read

def read(self)

send_file

def send_file(self, filepath, dest_filepath)

Sends to peer a file from filepath to write it on dest_filepath.

Args:

filepath (str): Path of the file to send.

dest_filepath (str): Path on peer where recieved file will be written to.

send_message

def send_message(self, action, args=(), kwargs=None)

Sends to peer message with specified action, arguments and keyword arguments.

Args:

action (str): action(command) to perform upon receiving. Should correspond with `action_string` of function registered in `message_callback()` on the peer.

args (tuple, optional): Arguments for the command. Defaults to ().

kwargs (dict, optional): Keyword arguments for the command. Defaults to None.

write

def write(self)

Class MessageManager

MessageManager class represents single incoming by TCP stream message and contains methods to decode and extract data from incoming data. It also contains static class methods for encoding various types of messages.

Messages in protocol implemented by this class consists of 3 parts:

Fixed-length (2 bytes) protoheader - contains length of json header
json header - contains information about message contents: length, encoding, byteorder, type of message and contents, etc.
content - contains actual contents of message (json information, bytes, etc.)

Attributes:

income_raw (bytes string): Holds incoming data bytes. Append incoming data to this attribute. It may not be empty after processing.

jsonheader (dict): Headers dictionary with information about message encoding and purpose. Would be populated when receiving and processing of the json header will be completed.

content (object): Would be populated when receiving and processing of the message will be completed. Defaults to None.

init

def __init__(self)


message = MessageManager()

process_message

def process_message(self)

Attempts processing the message. Chunks of income_raw would be consumed as different parts of the message will be processed. The result of processing (body of the message) will be available at content and jsonheader.