Fix log level in examples

[KevinWMatthews]

This sets logging.basicConfig() in several example applications so that it respects the user's selection at the CLI (see #2901).

Background

In order for Python to respect the log level that is set, logging.basicConfig() must be called.
If this is not done, then the first calls to logging functions will:

• call basicConfig() internally (see logging.debug())
• configure the handler lastResort

The lastResort handler defaults to a log level of WARNING, which I believe is why most log statements do not appear.

Examples

Info level

Setup:

% cd pymodbus/examples
% python3 -m venv .venv
% source .venv/bin/activate

For the server:

(.venv) % python3 server_async.py
INFO:/Users/kevin/src/pymodbus-dev/examples/server_async.py:### Create datastore
INFO:/Users/kevin/src/pymodbus-dev/examples/server_async.py:### start ASYNC server, listening on 5020 - tcp
INFO:asyncio:<Server sockets=(<asyncio.TransportSocket fd=7, family=30, type=1, proto=6, laddr=('::', 5020, 0, 0)>, <asyncio.TransportSocket fd=8, family=2, type=1, proto=6, laddr=('0.0.0.0', 5020)>)> is serving
2026-03-11 22:37:32,876 INFO  base:89 Server listening.
INFO:pymodbus.logging:Server listening.

For the client:

(.venv) % python3 client_async.py
INFO:__main__:### Create client object
INFO:__main__:### Client starting
INFO:__main__:### End of Program

Note that:

• __file__ has an impact
• INFO-level logs from server_async.py now appear
• INFO-level logs from client_async.py now appear

Debug level

Setup:

% cd pymodbus/examples
% python3 -m venv .venv
% source .venv/bin/activate

For the server

% python3 server_async.py --log debug
INFO:/Users/kevin/src/pymodbus-dev/examples/server_async.py:### Create datastore
INFO:/Users/kevin/src/pymodbus-dev/examples/server_async.py:### start ASYNC server, listening on 5020 - tcp
2026-03-11 22:40:24,986 DEBUG transport:265 Awaiting connections server_listener
DEBUG:pymodbus.logging:Awaiting connections server_listener
DEBUG:asyncio:Get address info None:5020, type=<SocketKind.SOCK_STREAM: 1>, flags=<AddressInfo.AI_PASSIVE: 1>
DEBUG:asyncio:Getting address info None:5020, type=<SocketKind.SOCK_STREAM: 1>, flags=<AddressInfo.AI_PASSIVE: 1> took 0.894ms: [(<AddressFamily.AF_INET6: 30>, <SocketKind.SOCK_STREAM: 1>, 6, '', ('::', 5020, 0, 0)), (<AddressFamily.AF_INET: 2>, <SocketKind.SOCK_STREAM: 1>, 6, '', ('0.0.0.0', 5020))]
INFO:asyncio:<Server sockets=(<asyncio.TransportSocket fd=7, family=2, type=1, proto=6, laddr=('0.0.0.0', 5020)>, <asyncio.TransportSocket fd=8, family=30, type=1, proto=6, laddr=('::', 5020, 0, 0)>)> is serving
2026-03-11 22:40:24,988 INFO  base:89 Server listening.
INFO:pymodbus.logging:Server listening.
DEBUG:asyncio:<Server sockets=(<asyncio.TransportSocket fd=7, family=2, type=1, proto=6, laddr=('0.0.0.0', 5020)>, <asyncio.TransportSocket fd=8, family=30, type=1, proto=6, laddr=('::', 5020, 0, 0)>)> got a new connection from ('127.0.0.1', 54996): <socket.socket fd=9, family=2, type=1, proto=0, laddr=('127.0.0.1', 5020), raddr=('127.0.0.1', 54996)>
2026-03-11 22:40:32,008 DEBUG transport:287 Connected to server
DEBUG:pymodbus.logging:Connected to server
2026-03-11 22:40:32,110 DEBUG transport:339 recv: 0x0 0x1 0x0 0x0 0x0 0x6 0x1 0x1 0x0 0x20 0x0 0x1 extra data:
DEBUG:pymodbus.logging:recv: 0x0 0x1 0x0 0x0 0x0 0x6 0x1 0x1 0x0 0x20 0x0 0x1 extra data:
2026-03-11 22:40:32,110 DEBUG base:72 Processing: 0x0 0x1 0x0 0x0 0x0 0x6 0x1 0x1 0x0 0x20 0x0 0x1
DEBUG:pymodbus.logging:Processing: 0x0 0x1 0x0 0x0 0x0 0x6 0x1 0x1 0x0 0x20 0x0 0x1
2026-03-11 22:40:32,110 DEBUG decoders:77 decoded PDU function_code(1 sub -1) -> ReadCoilsRequest(dev_id=0, transaction_id=0, address=32, count=1, bits=[], registers=[], status=1, retries=0)
DEBUG:pymodbus.logging:decoded PDU function_code(1 sub -1) -> ReadCoilsRequest(dev_id=0, transaction_id=0, address=32, count=1, bits=[], registers=[], status=1, retries=0)
2026-03-11 22:40:32,110 DEBUG transport:393 send: 0x0 0x1 0x0 0x0 0x0 0x4 0x1 0x1 0x1 0x1
DEBUG:pymodbus.logging:send: 0x0 0x1 0x0 0x0 0x0 0x4 0x1 0x1 0x1 0x1
2026-03-11 22:40:32,110 DEBUG transport:339 recv: 0x0 0x2 0x0 0x0 0x0 0x6 0x1 0x3 0x0 0x4 0x0 0x2 extra data:
DEBUG:pymodbus.logging:recv: 0x0 0x2 0x0 0x0 0x0 0x6 0x1 0x3 0x0 0x4 0x0 0x2 extra data:
2026-03-11 22:40:32,110 DEBUG base:72 Processing: 0x0 0x2 0x0 0x0 0x0 0x6 0x1 0x3 0x0 0x4 0x0 0x2
DEBUG:pymodbus.logging:Processing: 0x0 0x2 0x0 0x0 0x0 0x6 0x1 0x3 0x0 0x4 0x0 0x2
2026-03-11 22:40:32,110 DEBUG decoders:77 decoded PDU function_code(3 sub -1) -> ReadHoldingRegistersRequest(dev_id=0, transaction_id=0, address=4, count=2, bits=[], registers=[], status=1, retries=0)
DEBUG:pymodbus.logging:decoded PDU function_code(3 sub -1) -> ReadHoldingRegistersRequest(dev_id=0, transaction_id=0, address=4, count=2, bits=[], registers=[], status=1, retries=0)
2026-03-11 22:40:32,111 DEBUG transport:393 send: 0x0 0x2 0x0 0x0 0x0 0x7 0x1 0x3 0x4 0x0 0x11 0x0 0x11
DEBUG:pymodbus.logging:send: 0x0 0x2 0x0 0x0 0x0 0x7 0x1 0x3 0x4 0x0 0x11 0x0 0x11
DEBUG:asyncio:<_SelectorSocketTransport fd=9 read=polling write=<idle, bufsize=0>> received EOF
2026-03-11 22:40:32,111 DEBUG transport:356 -> transport: received eof
DEBUG:pymodbus.logging:-> transport: received eof
2026-03-11 22:40:32,111 DEBUG transport:299 Connection lost server due to None
DEBUG:pymodbus.logging:Connection lost server due to None
2026-03-11 22:40:32,111 DEBUG requesthandler:49 Handler for stream [server] has been canceled
DEBUG:pymodbus.logging:Handler for stream [server] has been canceled

For the client:

% python3 client_async.py --log debug
INFO:__main__:### Create client object
INFO:__main__:### Client starting
2026-03-11 22:40:32,007 DEBUG base:56 Connecting to 127.0.0.1:5020.
DEBUG:pymodbus.logging:Connecting to 127.0.0.1:5020.
2026-03-11 22:40:32,007 DEBUG transport:251 Connecting comm
DEBUG:pymodbus.logging:Connecting comm
2026-03-11 22:40:32,008 DEBUG transport:287 Connected to comm
DEBUG:pymodbus.logging:Connected to comm
DEBUG:asyncio:<asyncio.TransportSocket fd=6, family=2, type=1, proto=6, laddr=('127.0.0.1', 54996), raddr=('127.0.0.1', 5020)> connected to 127.0.0.1:5020: (<_SelectorSocketTransport fd=6 read=polling write=<idle, bufsize=0>>, <pymodbus.transaction.transaction.TransactionManager object at 0x10a270050>)
2026-03-11 22:40:32,109 DEBUG transport:393 send: 0x0 0x1 0x0 0x0 0x0 0x6 0x1 0x1 0x0 0x20 0x0 0x1
DEBUG:pymodbus.logging:send: 0x0 0x1 0x0 0x0 0x0 0x6 0x1 0x1 0x0 0x20 0x0 0x1
2026-03-11 22:40:32,110 DEBUG transport:339 recv: 0x0 0x1 0x0 0x0 0x0 0x4 0x1 0x1 0x1 0x1 extra data:
DEBUG:pymodbus.logging:recv: 0x0 0x1 0x0 0x0 0x0 0x4 0x1 0x1 0x1 0x1 extra data:
2026-03-11 22:40:32,110 DEBUG base:72 Processing: 0x0 0x1 0x0 0x0 0x0 0x4 0x1 0x1 0x1 0x1
DEBUG:pymodbus.logging:Processing: 0x0 0x1 0x0 0x0 0x0 0x4 0x1 0x1 0x1 0x1
2026-03-11 22:40:32,110 DEBUG decoders:77 decoded PDU function_code(1 sub -1) -> ReadCoilsResponse(dev_id=0, transaction_id=0, address=0, count=0, bits=[True, False, False, False, False, False, False, False], registers=[], status=1, retries=0)
DEBUG:pymodbus.logging:decoded PDU function_code(1 sub -1) -> ReadCoilsResponse(dev_id=0, transaction_id=0, address=0, count=0, bits=[True, False, False, False, False, False, False, False], registers=[], status=1, retries=0)
2026-03-11 22:40:32,110 DEBUG transport:393 send: 0x0 0x2 0x0 0x0 0x0 0x6 0x1 0x3 0x0 0x4 0x0 0x2
DEBUG:pymodbus.logging:send: 0x0 0x2 0x0 0x0 0x0 0x6 0x1 0x3 0x0 0x4 0x0 0x2
2026-03-11 22:40:32,111 DEBUG transport:339 recv: 0x0 0x2 0x0 0x0 0x0 0x7 0x1 0x3 0x4 0x0 0x11 0x0 0x11 extra data:
DEBUG:pymodbus.logging:recv: 0x0 0x2 0x0 0x0 0x0 0x7 0x1 0x3 0x4 0x0 0x11 0x0 0x11 extra data:
2026-03-11 22:40:32,111 DEBUG base:72 Processing: 0x0 0x2 0x0 0x0 0x0 0x7 0x1 0x3 0x4 0x0 0x11 0x0 0x11
DEBUG:pymodbus.logging:Processing: 0x0 0x2 0x0 0x0 0x0 0x7 0x1 0x3 0x4 0x0 0x11 0x0 0x11
2026-03-11 22:40:32,111 DEBUG decoders:77 decoded PDU function_code(3 sub -1) -> ReadHoldingRegistersResponse(dev_id=0, transaction_id=0, address=0, count=0, bits=[], registers=[17, 17], status=1, retries=0)
DEBUG:pymodbus.logging:decoded PDU function_code(3 sub -1) -> ReadHoldingRegistersResponse(dev_id=0, transaction_id=0, address=0, count=0, bits=[], registers=[17, 17], status=1, retries=0)
INFO:__main__:### End of Program
DEBUG:asyncio:Close <_UnixSelectorEventLoop running=False closed=False debug=True>

Open Questions

Should examples call logging.getLogger(__name__) instead of logging.getLogger(__file__)?
This is recommended by the docs and gives log messages that are more brief.

[janiversen]

please see comment on the corresponding issue.

[janiversen]

LGTM, thanks.