Asio library for C++

1 Introduction

Asio is a cross-platform C++ library, commonly used for network programming, low-level I/O programming, etc. (low-level I/O). Its structural framework As follows:

2 Using Asio

##2.1 Download

Asio library is divided into Boost version and non-Boost version. Please go to the official website to download.

2.2 Configuration

1) Using Qt 5.9.1, add the following configuration to its .pro project file: Note

ASIO_STANDALONE In the non-Boost version,

INCLUDEPATH += $$PWD/../../serialport/asio-1.10.8/includeDEFINES += ASIO_STANDALONE

2) If you use VS 2015, then

ASIO_STANDALONE is configured as follows Shown:

2.3 Code example

The following is a simple serial communication example. The main steps are:

Create Serial port --> Configuration parameters --> Read and write data --> Enable event loop

#include <functional>#include "asio.hpp"#include <QDebug>using namespace asio;// 存储接收到的数据char kBuf[16];// 声明回调函数void PrintBuf();int main()
{    // 串口 COM1    io_service iosev;
    serial_port port(iosev, "COM1");    // 参数设置：波特率、流控、奇偶校验、停止位、数据位
    port.set_option(serial_port::baud_rate(115200));
    port.set_option(serial_port::flow_control(serial_port::flow_control::none));
    port.set_option(serial_port::parity(serial_port::parity::none));
    port.set_option(serial_port::stop_bits(serial_port::stop_bits::one));
    port.set_option(serial_port::character_size(8));    // 向串口写数据
    write(port, buffer("Hello Asio", 16));    // 从串口读数据（异步）    port.async_read_some(buffer(kBuf),std::bind(PrintBuf));    // 开启事件循环    iosev.run();
}// 打印接收的数据void PrintBuf()
{
    qDebug() << kBuf;
}

3 DB9 serial port

When running the above program, you will find a problem: the program first sends/writes

to the serial port COM1, "Hello Asio" data, and then go to to receive/read data. For a serial port, the data will not be received.

On the back of the desktop computer, the DB9 serial port pin numbers are as follows:

Among them, 2 --> RxD, is the pin for receiving data; 3 --> TxD, is the pin for sending data.

In order for the above program to run successfully, you can

short pin 2 and pin 3 before running the program. In this way, you can both send and receive data

4 Virtual serial port

If you use a laptop, there is generally no serial port. In this case, there are two options:

First, use the

USB to serial port data cable and install the corresponding driver, then you can communicate with the device with a serial port;

Second, use

Virtual Serial Port Software to create a virtual serial port, for example, Configure Virtual Serial Port Driver

and with

Serial Port Debugging Tool, you can flexibly Debugging the serial port program

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