4. Communication module

The communication module handles the low level communication between the server and the clients.

It provides functions to send and receive a request with arguments to a given socket.

It can start a connection with the server and close a socket. It also keep track of sockets to close them automatically at the end of the program.

4.1. Examples

from fand.communication import *
s = connect('myserver.example.com', 9999)
send(s, Request.GET_PWM, 'myshelf1')
req, args = recv(s)
if req == Request.SET_PWM:
    print("The fan speed of", args[0], "is", args[1])
else:
    print("The server did not answer the expected request")

4.2. Python API

4.2.1. Request

class fand.communication.Request

Bases: enum.Enum

Enumeration of known requests

ACK = 'ack'

Acknowledge a previously received Request

DISCONNECT = 'disconnect'

Notification of disconnection

GET_PWM = 'get_pwm'

Request for a Request.SET_PWM to get current PWM

GET_RPM = 'get_rpm'

Request for a Request.SET_RPM to get current RPM

PING = 'ping'

Request for a Request.ACK

SET_PWM = 'set_pwm'

Give the current PWM

SET_PWM_EXPIRE = 'set_pwm_expire'

Set the expiration date of the PWM override

SET_PWM_OVERRIDE = 'set_pwm_override'

Override the PWM value

SET_RPM = 'set_rpm'

Give the current RPM

4.2.2. add_socket

fand.communication.add_socket(sock: socket.socket) → None

Add sock to the set of managed sockets

It can be removed with reset_connection() and will automatically be when fand.util.terminate() is called.

Parameters:sock – Socket to add Raises:TerminatingError – Trying to add a socket but fand.util.terminating() is True

4.2.3. is_socket_open

fand.communication.is_socket_open(sock: socket.socket) → bool

Returns True if sock is currently managed by this module

This will be False after a socket has been closed with reset_connection().

Parameters:sock – Socket to test

4.2.4. send

fand.communication.send(sock: socket.socket, request: fand.communication.Request, *args) → None

Send a request to a remote socket

Parameters:

• sock – Socket to send the request to
• request – Request to send
• args – Request arguments

Raises:

• UnpicklableError – Given data cannot be pickled by pickle
• FandTimeoutError – Connection timed out
• SendReceiveError – Error while sending the data

4.2.5. recv

fand.communication.recv(sock: socket.socket) → Tuple[fand.communication.Request, Tuple]

Receive a request from a remote socket, returns (request, args)

Parameters:

sock – Socket to receive the request and its arguments from

Raises:

• FandTimeoutError – Connection timed out
• SendReceiveError – Error while receiving the data
• FandConnectionResetError – No data received or Request.DISCONNECT received
• CorruptedDataError – Invalid data received

4.2.6. connect

fand.communication.connect(address: str, port: int) → socket.socket

Connect to server and returns socket

Parameters:

• address – Server address
• port – Server port

Raises:

• FandTimeoutError – Connection timed out
• ConnectionFailedError – Failed to connect to remote socket

4.2.7. reset_connection

fand.communication.reset_connection(client_socket: socket.socket, error_msg: Optional[str] = None, notice: bool = True) → None

Closes a connection to a client

Parameters:

• client_socket – Socket to close
• error – Error to send
• notice – Send a notice about the reset to the remote socket