c++ - 无法绑定(bind)到套接字

Question

代码:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
// #include <thread>
#include <arpa/inet.h>
#include <iostream>

using namespace std;

#define PORT 8888
#define BACKLOG 5

int main(int argc, char const *argv[]) {

    int status;
    struct addrinfo hints,
                    *res,
                    *temp;

    char ipstr [INET6_ADDRSTRLEN];
    int socket_fd;

    memset (&hints, 0, sizeof(hints));
    hints.ai_family = AF_UNSPEC;        // Allows both IPv4 and IPv6
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = AI_PASSIVE;        // Allows automatic fill-up of IP (allows using localhost)

    if ((status = getaddrinfo (NULL , "8000", &hints, &res)) != 0 ) {
        cout << "[-] Error: " << gai_strerror (status) << endl;
        exit (EXIT_FAILURE);
    }

    socket_fd = socket (res->ai_family, res->ai_socktype, res->ai_protocol);
    if (socket_fd == -1) {
        cout << "[-] Error : Socket couldn't be created" << endl;
        exit (EXIT_FAILURE);
    }

    if (bind (socket_fd, res->ai_addr, res->ai_addrlen) == -1 ) {
        cout << "[-] Error: Failed to bind to port" << endl;
        exit (EXIT_FAILURE);
    }

    if (connect (socket_fd, res->ai_addr, res->ai_addrlen) == -1) {
        cout << "[-] Error: Failed to connect to remote user" << endl;
        exit (EXIT_FAILURE);
    }

    freeaddrinfo (res);        // free the linked list returned by getaddrinfo ()
    return 0;
}

代码正在返回:
[-] 错误:绑定(bind)端口失败

无论我将 NULL 放在 getaddrinfo () 的第一个参数上(让它监听 localHost)还是提供一些地址，它都无法将端口绑定(bind)到套接字。正如我通过更改端口值尝试的那样，该端口可用。代码有什么问题？

Answer 1

代码很好，所以当第一次执行时，一切都按预期工作。但是，后续执行同一个程序会报

[-] Error: Failed to bind to port

如果你运行 netstat --tcp --numeric | grep 8000 你会看到8000端口的socket处于TIME_WAIT状态:

bash-4.2$ netstat --tcp --numeric | grep 8000
tcp        0      0 127.0.0.1:8000          127.0.0.1:8000          TIME_WAIT

表示连接已关闭，因此它将在操作系统指定的超时时间内终止(默认为四分钟)。超时到期后，程序将无错误地执行(同样只有一次)。