利用ptmx搭建本地虚拟串口回环测试环境

留个备份,执行这个搭建程序可以在当前目录生成ttyNeo1和ttyNeo2两个互连的虚拟串口,在Linux上写上位机和下位机串口通信程序时就不需要利用物理串口测试了。

#define _XOPEN_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <poll.h>

static int alive = 0;
static char buf[8*1024] = {0};

static void neo_handler(int sig)
{
    printf("got signal(%d)\n", sig);
    alive = 0;
}

int main(int argc, char **argv)
{
    int ret = 0;
    int m1 = 0;
    int m2 = 0;
    char *pts = NULL;
    struct pollfd pollfds[2];
    signal(SIGTERM, neo_handler);
    signal(SIGINT, neo_handler);
    m1 = open("/dev/ptmx", O_RDWR);
    if (m1 < 0) {
        printf("open /dev/ptmx failed, errno=%d(%s)\n", errno, strerror(errno));
        return -1;
    }
    grantpt(m1);
    unlockpt(m1);
    m2 = open("/dev/ptmx", O_RDWR);
    if (m2 < 0) {
        printf("open /dev/ptmx failed, errno=%d(%s)\n", errno, strerror(errno));
        goto err_m2;
    }
    grantpt(m2);
    unlockpt(m2);
    pts = ptsname(m1);
    if (!pts)
        goto err_pts;
    remove("./ttyNeo1");
    ret = symlink(pts, "./ttyNeo1");
    if (ret < 0) {
        printf("create ./ttyNeo1 failed, errno=%d(%s)\n", errno, strerror(errno));
        goto err_pts;
    }
    pts = ptsname(m2);
    remove("./ttyNeo2");
    ret = symlink(pts, "./ttyNeo2");
    if (ret < 0) {
        printf("create ./ttyNeo2 failed, errno=%d(%s)\n", errno, strerror(errno));
        goto err_pts;
    }
    memset(&pollfds, 0, sizeof(pollfds));
    pollfds[0].fd = m1;
    pollfds[0].events = POLLIN;
    pollfds[1].fd = m2;
    pollfds[1].events = POLLIN;
    alive = 1;
    while (alive) {
        ret = poll(&pollfds[0], 2, 500);
        if ((ret < 0) && (errno == EINTR) || (ret == 0))
            continue;
        else if (ret < 0) {
            printf("poll failed, errno=%d(%s)\n", errno, strerror(errno));
            break;
        }
        if (pollfds[0].revents & POLLIN) {
            memset(buf, 0, sizeof(buf));
            ret = read(m1, buf, sizeof(buf));
            if (ret > 0)
                write(m2, buf, ret);
            pollfds[0].revents = 0;
        }
        if (pollfds[1].revents & POLLIN) {
            memset(buf, 0, sizeof(buf));
            ret = read(m2, buf, sizeof(buf));
            if (ret > 0)
                write(m1, buf, ret);
            pollfds[1].revents = 0;
        }
    }
err_pts:
    close(m2);
    m2 = -1;
err_m2:
    close(m1);
    m1 = -1;
    return 0;
}

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