Define tasks

Run and intialize a bgpy server on a host, which starts listening to the provided port. After starting the server, a INIT message with the init_task, exec_task() and exit_task() tasks are send to the server in order to complete the initialization.

• Initialization task

Task that runs once during initialization and can be used to set up the server. The return value of this function must be a dict, which is then passed to the exec_task function with every request by a client.

def init_task(client_socket: ClientSocket) -> dict:
    init_args = {"request_count": 0, "value": 1000}
    return init_args

• Execution task

Task that is called each time a request is made by a client to the server. In this task the message from the execute method of the Client class is interpreted and an action has to be defined accordingly. The input of the exec_task is the return value of the last exec_task function call (or if never called, the return value from the init_task). Using the function respond om the server, a second response can be sent to the client after the standard confirmation of the receipt of the message by the server.

def exec_task(
    client_socket: ClientSocket, init_args: dict, exec_args: dict
) -> dict:
    init_args["request_count"] += 1
    if exec_args["command"] == "increase":
            init_args["value"] += exec_args["value_change"]
    if exec_args["command"] == "decrease":
            init_args["value"] -= exec_args["value_change"]
    return init_args

• Exit task

Task that is executed once if an exit message is sent to the server by the terminate method of the Client class. The input of the exit_task is the return value of the last exec_task function call (or if never called, the return value from the init_task). With respond a second message can be sent to the client, if the client is set to be waiting for a second response (Client.terminate(..., await_response=True).

def exit_task(
    client_socket: ClientSocket, init_args: dict, exit_args: dict
) -> None:
    init_args["request_count"] += 1
    init_args["status"] = "Exited."
    respond(client_socket, init_args)
    return None

Note: If the client is set to wait for a second response (Client.execute(..., await_response=True or Client.terminate(..., await_response=True) it is important to handle this on the server side by sending a response to the client using respond. Otherwise the client may be waiting forever as there is no timeout specified.

Run the server

Run an example background process on localhost and send requests using client sockets:

from bgpy import Client, Server
from bgpy.example.tasks import init_task, exec_task, exit_task

HOST = "127.0.0.1"
PORT = 54321

# Optionally set a token for the client authentication
from bgpy import token_create
TOKEN = token_create()

# Create server context
server = Server(host=HOST, port=PORT, token=TOKEN)

# Start server in background from context
server.run_background()

# Bind client to server context
client = Client(host=HOST, port=PORT, token=TOKEN)

# Send INIT message from client to server, receive OK
response = client.initialize(init_task, exec_task, exit_task)

# Execute command 'increase' with value on server, receive OK
response = client.execute({"command": "increase", "value_change": 10})

# Execute command 'decrease' with value on server, receive OK
response = client.execute({"command": "decrease", "value_change": 100})

# Terminate and wait for response, receive OK with values
response = client.terminate(await_response=True)