Transport¶

class nmeasim::io::Transport · Library API

Abstract output channel: TCP server or client, UDP, WebSocket server, serial port, file, log or standard output.

#include <nmeasim/io/transport.hpp>

Inherits QObject

Inherited by nmeasim::io::FileTransport, nmeasim::io::LogTransport, nmeasim::io::SerialTransport, nmeasim::io::StdoutTransport, nmeasim::io::TcpClientTransport, nmeasim::io::TcpServerTransport, nmeasim::io::UdpTransport, nmeasim::io::WebSocketServerTransport

Declared in src/io/include/nmeasim/io/transport.hpp (line 35)

A transport moves through the life cycle State::Closed, State::Opening, State::Open and back to State::Closed, or to State::Failed when opening fails or the device goes away. Only an open transport delivers what write is given; every implementation silently drops lines in any other state. Transports send the payload as given, byte for byte, except LogTransport, which records each line with a timestamp in front and a single line feed at the end.

Implementations use Qt sockets, devices and timers, so a transport is used from the thread that created it, and that thread runs a Qt event loop: asynchronous events (a client connecting, a connection dropping, a reconnection timer) are processed there and the corresponding signals are emitted there.

Summary¶

Public types

Name	Description
`State`	Life-cycle state of a transport, reported through `state_changed`.

Public member functions

Name	Description
`Transport()`	Creates a transport in the `State::Closed` state.
`description()`	Returns a human-readable summary of the channel and its settings.
`open()`	Starts listening, connecting or opening the device or file.
`close()`	Stops listening, disconnects or closes the file, then moves to `State::Closed`.
`write()`	Sends one line to every connected consumer.
`state()`	Returns the current life-cycle state.
`is_open()`	Returns whether the transport is in `State::Open`.
`last_error()`	Returns the message of the most recent failure.
`client_count()`	Returns the number of consumers currently attached.
`bytes_written()`	Returns the total number of bytes written to consumers since construction.

Signals

Name	Description
`state_changed()`	Emitted when the life-cycle state changes, synchronously from inside `open`, `close` or `fail`, or from an asynchronous socket or device event.
`error_occurred()`	Emitted for every error, whether or not it moves the transport to `State::Failed`.
`client_count_changed()`	Emitted when a client connects or disconnects.

Protected member functions

Name	Description
`set_state()`	Moves to `state`.
`fail()`	Records an error and moves to `State::Failed`.
`count_bytes()`	Adds a write result to `bytes_written`.

Private data members

Name	Description
`state_`	Current life-cycle state; changed only through `set_state`.
`last_error_`	Message of the most recent failure; empty until `fail` is first called.
`bytes_written_`	Bytes written since construction, summed over every consumer.

Public types¶

State¶

enum class State

Life-cycle state of a transport, reported through state_changed.

Enumerator	Value	Description
`Closed`		Not opened yet, or closed by `close`. The initial state.
`Opening`		Opening, or waiting to reconnect (TCP client) after the peer dropped the connection.
`Open`		Ready: `write` delivers data.
`Failed`		Opening failed or the device went away; `last_error` says why. `open` may be called again. A TCP client keeps retrying by itself in this state.

Declared in src/io/include/nmeasim/io/transport.hpp:40

Public member functions¶

Transport()¶

explicit Transport(QObject* parent = nullptr)

Creates a transport in the State::Closed state.

Parameters

Name	Type	Description
`parent`	`QObject*`	Qt parent that owns the transport; null leaves ownership to the caller, as `SimulationRunner` does with its `std::unique_ptr`.

Declared in src/io/include/nmeasim/io/transport.hpp:58 · defined in src/io/src/transport.cpp:10

description()¶

virtual QString description() const = 0

Returns a human-readable summary of the channel and its settings.

Returns QString: A one-line text such as TCP server on 127.0.0.1:10110 or Serial port /dev/ttyUSB0 at 4800 baud, used in error reports and status displays.

Declared in src/io/include/nmeasim/io/transport.hpp:64

open()¶

virtual bool open() = 0

Starts listening, connecting or opening the device or file.

On success the transport ends in State::Open, or in State::Opening when the connection is made asynchronously (TCP client). On failure it moves to State::Failed and emits error_occurred. Emits state_changed for every state it passes through.

Returns bool: False when opening fails immediately; true otherwise. Asynchronous failures are reported later through error_occurred and state_changed.

Declared in src/io/include/nmeasim/io/transport.hpp:75

close()¶

virtual void close() = 0

Stops listening, disconnects or closes the file, then moves to State::Closed.

Stops any automatic reconnection and detaches every client. Safe to call in any state, including when already closed. Emits state_changed when the state changes.

Declared in src/io/include/nmeasim/io/transport.hpp:80

write()¶

virtual void write(const QByteArray& line) = 0

Sends one line to every connected consumer.

Silently drops the line while the transport is not open. Write errors are not reported by the return value; transports that detect them report them through error_occurred.

Parameters

Name	Type	Description
`line`	`const QByteArray&`	One complete line, terminator included.

Declared in src/io/include/nmeasim/io/transport.hpp:89

state()¶

State state() const noexcept

Returns the current life-cycle state.

Returns State: The state last set by the implementation; State::Closed initially.

Declared in src/io/include/nmeasim/io/transport.hpp:94

is_open()¶

bool is_open() const noexcept

Returns whether the transport is in State::Open.

Returns bool: True in State::Open, false in every other state.

Declared in src/io/include/nmeasim/io/transport.hpp:98

last_error()¶

QString last_error() const

Returns the message of the most recent failure.

Returns QString: The message passed to the last call of fail; empty when none has occurred. It is not cleared when the transport opens again.

Declared in src/io/include/nmeasim/io/transport.hpp:103

client_count()¶

virtual int client_count() const

Returns the number of consumers currently attached.

The default suits point-to-point transports; the TCP and WebSocket servers override it with their number of connected clients.

Returns int: 1 while open and 0 otherwise for point-to-point transports; the number of connected clients for servers.

Declared in src/io/include/nmeasim/io/transport.hpp:111

bytes_written()¶

qint64 bytes_written() const noexcept

Returns the total number of bytes written to consumers since construction.

Returns qint64: Bytes summed over every consumer, so a server with three clients counts each line three times. Greetings and log headers are included; failed writes are not.

Declared in src/io/include/nmeasim/io/transport.hpp:116

Signals¶

state_changed()¶

void state_changed(nmeasim::io::Transport::State state)

Emitted when the life-cycle state changes, synchronously from inside open, close or fail, or from an asynchronous socket or device event.

Not emitted when the new state equals the current one.

Parameters

Name	Type	Description
`state`	`nmeasim::io::Transport::State`	The new state.

Declared in src/io/include/nmeasim/io/transport.hpp:125

error_occurred()¶

void error_occurred(const QString& message)

Emitted for every error, whether or not it moves the transport to State::Failed.

Emitted synchronously by fail, and by implementations for socket errors that do not end the transport, such as a TCP client losing its peer before reconnecting.

Parameters