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我需要为某些程序生成端口号。谷歌告诉，与零端口绑定生成绑定未使用的端口。我要绑定零端口，记住它的号码，关闭端口。试图这样做？但 netstat 看不到我的程序的端口。Linux 2.6.27

int sfd;
struct sockaddr_in my_addr;

sfd = socket(PF_INET , SOCK_STREAM, 0);
if (sfd == -1)
{
    printf("socket error\n");
    return -1;
}

memset(&my_addr, 0, sizeof(struct sockaddr_in ));
my_addr.sin_family = AF_INET;
my_addr.sin_addr.s_addr = INADDR_ANY;
my_addr.sin_port = 0;

if (bind(sfd, (struct sockaddr_in *) &my_addr,
        sizeof(struct sockaddr_in)) == -1)
    printf("bind error\n");

if (listen(sfd, LISTEN_BACKLOG) == -1)
    printf("listen error\n");
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1 回答 1

1

bind()期望 asockaddr*不是 a sockaddr_in*：

bind(sfd, (struct sockaddr *) &my_addr, sizeof(my_addr))

除此之外，我没有看到任何其他错误。绑定到端口 0 是绑定到随机可用端口的正确方法。如果bind()并且listen()不报告失败，那么 netstat 应该会看到一个开放的端口。用于getsockname()找出bind()实际选择的端口，例如：

int sfd = socket(PF_INET , SOCK_STREAM, 0);
if (sfd == -1)
{
    printf("socket error: %d\n", errno);
    return -1;
}

struct sockaddr_in my_addr;
memset(&my_addr, 0, sizeof(my_addr));
my_addr.sin_family = AF_INET;
my_addr.sin_addr.s_addr = INADDR_ANY;
my_addr.sin_port = 0;

if (bind(sfd, (struct sockaddr *) &my_addr, sizeof(my_addr)) == -1)
{
   printf("bind error: %d\n", errno);
   close(sfd);
   return -1;
}

if (listen(sfd, LISTEN_BACKLOG) == -1)
{
    printf("listen error: %d\n", errno);
    close(sfd);
    return -1;
}

memset(&my_addr, 0, sizeof(my_addr));
socklen_t my_addrlen = sizeof(my_addr);

if (getsockname(sfd, (struct sockaddr *) &my_addr, &my_addrlen ) == -1)
{
    printf("getsockname error: %d\n", errno);
    close(sfd);
    return -1;
}

printf("listening on port: %hu\n", ntohs(my_addr.sin_port));
于 2014-04-22T08:52:10.710 回答