Question

这是我的代码：

int main(int argc, char * argv[])
{
    if (1 == argc) {  // if nothing go in 
        printf("Usage: %s <port>\n", argv[0]);
        exit(-0);
    }

    int port = strtol(argv[1], NULL, 10); //pass
    if (0 == port) {
        perror("Invalid port");
        exit(-1);
    }

    struct sigaction sa;
    sa.sa_handler = &handle_sigchld;
    sigemptyset(&sa.sa_mask);
    sa.sa_flags = SA_RESTART | SA_NOCLDSTOP;
    if (sigaction(SIGCHLD, &sa, 0) == -1) {
        perror("Unable to register sigaction");
        exit(-2);
    }

    int s = socket(AF_INET, SOCK_STREAM, 0);
    if (-1 == s) {
        perror("Unable to create server socket");
        exit(-3);
    }

    int optval = 1;
    if (0 != setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval))) {
        perror("Unable to setsockopt");
        exit(-4);
    }

    struct sockaddr_in bind_addr = {
        .sin_family = AF_INET,
        .sin_port = htons(port)
    };

    if (0 != bind(s, (struct sockaddr *) &bind_addr, sizeof(bind_addr))) {
        perror("Unable to bind socket");
        exit(-5);
    }

    if (0 != listen(s, 10)) {
        perror("Unable to listen");
        exit(-6);
    }

    while (1) {
        int s_ = accept(s, NULL, NULL); 

        sleep(BRUTE_FORCE_TIMEOUT); //here is the stop !!!(but after I delete this, it still stops but in the first line of this while loop)

        if (-1 == s_) {
            perror("Unable to accept");
            continue;
        }

        pid_t child_pid = fork();
        if (-1 == child_pid) {
            perror("Unable to fork");
            goto accept_cleanup;
        }

        if (0 == child_pid) {
            close(s);
            handle(s_);
            exit(0);
        }

accept_cleanup:
        close(s_);
    }

    exit(0);
}

void handle(int s)
{
    char inbuf[4096];
    dup2(s, 0);
    dup2(s, 1);
    setbuf(stdout, NULL);
    alarm(ALARM_TIMEOUT_SEC);
    printf("crackme> ");
    if (NULL == fgets(inbuf, sizeof(inbuf), stdin))
    {
        return;
    }
    right_trim(inbuf);
    if(is_correct(inbuf))
    {
        printf("Good job!\n");
    }
}

要运行此程序，我需要运行程序名称和端口号。例如：

./my_file 6000

问题是当我运行端口已经运行时，我收到一个错误，表明该端口已在使用中。如果我尝试使用端口0运行它，我会收到端口无效的错误：成功。如果我只使用一个随机端口运行它，Linux下行线并没有任何反应。

当我在gdb中调试它时，它会在sleep行停止，所以我删除了这一行，然后它再次停止，但现在在while循环的第一行（while (1) { int s_ = ...）。

为什么会这样？

为什么此代码的端口已被使用＆＃39;错误？

0 个答案: