Question

我在下面写了多线程TCP客户端，它基本上产生了一个单独的线程来接收数据，但数据是在主线程中写入的，只是在标准输入上从用户那里获取了输入。

现在，按下了ctrl ^ D然后实现从循环中出来（围绕getline（）调用）并关闭套接字描述符但是在线上没有看到FIN。但是，用shutdown（）替换close（）会产生影响。使用close（）时，没有FIN在线路上发送，但是关闭（fd，SHUT_WR）FIN在线路上发送？

为什么会有这种差异？

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>

void *receiver (void *arg);

pthread_t thrid;

int sockfd;

int reUse = 0;

int
main (int argc, char *argv[])
{
    struct sockaddr_in servaddr;

    struct sockaddr_in clntaddr;

    char *line;

    size_t len = 0;

    size_t read;

    int bytes;

    if (argc < 6)
    {
        printf
            ("Usage:%s <Server Ipv4 address> <Server Port> <SO_REUSEADDR Yes(1)/No(0))> <Close(0)/SHUT_RD(1)/SHUT_WR(2)/SHUT_RDWR(3)> <sleep (in sec)> [Client IPv4 address] [Client Port]\n",
             argv[0]);
        return -1;
    }

    /*
     * AF_INET, AF_INET6, AF_UNIX, AF_NETLINK
     * SOCK_STREAM (TCP), SOCK_DGRAM (UDP), SOCK_RAW
     */
    if ((sockfd = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP)) == -1)
    {
        printf ("Failed to create socket: %s\n", strerror (errno));
        return -1;
    }

    /*
     * set SO_REUSEADDR option for the UDP server socket
     */
    reUse = atoi (argv[3]);
    if (reUse)
    {
        int i = 1;

        setsockopt (sockfd, SOL_SOCKET, SO_REUSEADDR, (void *) &i,
                    sizeof (i));
    }

    bzero (&clntaddr, sizeof (struct sockaddr_in));

    if (argc == 8)
    {
        printf ("doing bind......\n");
        clntaddr.sin_family = AF_INET;
        clntaddr.sin_port = htons (atoi (argv[7]));
        inet_aton (argv[6], &clntaddr.sin_addr);

        if (bind
            (sockfd, (struct sockaddr *) &clntaddr,
             sizeof (struct sockaddr_in)) == -1)
        {
            perror ("Failed to bind");
            close (sockfd);
            return -1;
        }
    }

    bzero (&servaddr, sizeof (struct sockaddr_in));

    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons (atoi (argv[2]));
    inet_aton (argv[1], &servaddr.sin_addr);

    if (-1 ==
        connect (sockfd, (struct sockaddr *) &servaddr,
                 sizeof (struct sockaddr_in)))
    {
        printf ("Failed to connect: %s\n", strerror (errno));
        return -1;
    }

    if (pthread_create (&thrid, NULL, receiver, NULL) < 0)
    {
        printf ("Failed to create thread\n");
    }

    while ((read = getline (&line, &len, stdin)) != -1)
    {
        bytes = send (sockfd, line, len, 0);
        if (bytes < 0)
        {
            if (errno == EINTR)
                continue;
            else
                printf ("%Read error %s\n", pthread_self (),
                        strerror (errno));
        }

    }

    if (0 == atoi (argv[4]))
    {
        printf ("doing close()....\n");
        close (sockfd);
    }
    else if (1 == atoi (argv[4]))
    {
        printf ("doing shutdown(..., SHUTRD)....\n");
        shutdown (sockfd, SHUT_RD);
    }
    else if (2 == atoi (argv[4]))
    {
        printf ("doing shutdown(..., SHUTWR)....\n");
        shutdown (sockfd, SHUT_WR);
    }
    else if (3 == atoi (argv[4]))
    {
        printf ("doing shutdown(..., SHUTRDWR)....\n");
        shutdown (sockfd, SHUT_RDWR);
    }

    if (line)
        free (line);

    sleep (atoi (argv[5]));
}

void *
receiver (void *arg)
{
    char buff[512];

    int bytes;

    while (1)

    {
        bytes = recv (sockfd, buff, sizeof (buff), 0);
        if (bytes < 0)
        {
            if (errno == EINTR)
                continue;
            else
                printf ("%Read error %s\n", pthread_self (),
                        strerror (errno));
            pthread_exit (-1);
        }
        else if (bytes == 0)
        {
            printf ("connection closed by Peer\n");
            close(sockfd);
            pthread_exit (-1);
        }
        else
        {
            printf ("Msg Received:%s\n", buff);
        }
    }
}

Answer 1

呼叫关闭（WR）将发送FIN，但关闭有一点不同：如果fd引用计数不等于0将不发送FIN。

Answer 2

你可以在关闭（套接字）之前使用shutdown（socket，SHUT_WR）

对于多线程TCP客户端执行'close（）'时未发送TCP FIN

2 个答案: