Linux下的虚拟终端（可用于在本机上模拟串口进行调试）

浏览数：42 / 时间：2015年06月20日

转载：http://blog.sina.com.cn/s/blog_6cb543ef0100x90j.html

今日编写了一个串口通讯程序，但是本机只有一个串口，无法验证程序的正确性，于是想到在linux下面增加一对虚拟串口

Python：

#! /usr/bin/env python
#coding=utf-8

import pty
import os
import select

def mkpty():
    # 打开伪终端
    master1, slave = pty.openpty()
    slaveName1 = os.ttyname(slave)
    master2, slave = pty.openpty()
    slaveName2 = os.ttyname(slave)
    print ‘\nslave device names: ‘, slaveName1, slaveName2
    return master1, master2

if __name__ == "__main__":

    master1, master2 = mkpty()
    while True:
        rl, wl, el = select.select([master1,master2], [], [], 1)
        for master in rl:
            data = os.read(master, 128)
            print "read %d data." % len(data)
            if master==master1:
                os.write(master2, data)
            else:
                os.write(master1, data)

程序名叫mkptych.py，在终端里运行“python mkptych.py &”，这样就可以生成一个基于pty（伪终端）的虚拟端口对，两个设备名会显示在终端里。然后就可以利用这两个设备名在本机上进行虚拟串口之类的调试，使用完后用ps查看这个python进程的pid号，然后kill掉即可。

下面编写一个用上述虚拟串口的使用程序：

receiver.c

#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
#include <math.h>

#define MAX_BUFFER_SIZE 512

int fd, s;

int open_serial()
{
    //这里的/dev/pts/27是使用mkptych.py虚拟的两个串口名字之一
    fd = open("/dev/pts/27", O_RDWR|O_NOCTTY|O_NDELAY);
    if(fd == -1)
    {
        perror("open serial port error!\n");
        return -1;
    }

    printf("open /dev/ttyS0.\n");
    return 0;
}

int main()
{
    char hd[MAX_BUFFER_SIZE], *rbuf;
    int flag_close, retv;
    struct termios opt;

    retv = open_serial();
    if(retv < 0)
    {
        printf("Open serrial port error!\n");
        return -1;
    }

    tcgetattr(fd, &opt);
    cfmakeraw(&opt);
    cfsetispeed(&opt, B9600);
    cfsetospeed(&opt, B9600);
    tcsetattr(fd, TCSANOW, &opt);
    rbuf = hd;
    printf("Ready for receiving data...\n");

    while(1)
    {
        while((retv = read(fd, rbuf, 1)) > 0)
            printf( "%c ", *rbuf);
    }

    printf("\n");
    flag_close = close(fd);
    if(flag_close == -1)
        printf("Close the device failure!\n");

    return 0;
}

send.c

#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>

#define MAX_BUFFER_SIZE 512

int fd, flag_close;

int open_serial()
{
    //这里的/dev/pts/28是使用mkptych.py虚拟的两个串口名字之一
    fd = open("/dev/pts/28", O_RDWR | O_NOCTTY | O_NONBLOCK);
    if(fd == -1)
    {
        perror("open serial port error!\n");
        return -1;
    }

    printf("Open serial port success!");
    return 0;
}

int main(int argc, char* argv[])
{
    char sbuf[] = {"Hello, this is a serial port test!\n"};
    int retv;
    struct termios option;

    retv = open_serial();
    if(retv < 0)
    {
        perror("open serial port error!\n");
        return -1;
    }

    printf("Ready for sending data...\n");

    tcgetattr(fd, &option);
    cfmakeraw(&option);

    cfsetispeed(&option, B9600);
    cfsetospeed(&option, B9600);

    tcsetattr(fd, TCSANOW, &option);

    int length = sizeof(sbuf);
    retv = write(fd, sbuf, length);
    if(retv == -1)
    {
        perror("Write data error!\n");
        return -1;
    }

    printf("The number of char sent is %d\n", retv);
    return 0;
}